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How to shoot a scene of someone riding a bike?
I'm shooting a short film and there is a scene I'd like to film where a guy is biking and the camera follows him through his bike ride. All I have to film on is a Sony a3000 camera, I don't own anything fancy. How can I film this scene without buying any expensive equipment?

Well, its a bit of a generic question.
Almost like asking how to take a movie like shot using your camera.
The answer is equally generic.

Lighting, to prevent blowout or shadows take the shot when its cloudy, or near sunrise or sunset. (Unless you wanted a grunge harsh hot feel and maybe over exposed is the effect you are after, so take it at noon).
Make sure the light is behind you so you capture the image flush.
Make sure you take shots in scenes. A closeup of peddling (running alongside with a macro lens can work). Take a closeup shot. Take a shot that first places them in the scene (unless you are adding mystery and sometimes you place that scene at the end).
Tell a story, have an element in the foreground like a thumbs up to hitch a ride, out of focus is the rider coming up, then comes into focus the thumb is blurred. Then cut reaction shot, or maybe maybe headphones not seeing shot. etc, I mean just go with the story, and tell the story with your shots.
I guess I could also go with settings, I am a big fan of large apertures (low f stops) like f2.0 - f4.0. And high shutter speed 1/125th or higher to minimize blur on fast moving objects, again depending how you want the end result to look, all these rules can be broken. Large apertures (low f stops)  tends to create a bokeh effect (out of focus the background if focus is on subject) making it obvious to the audience what is the focus of the story.

High shutter speed will reduce the film-like quality of the footage, especially if your goal is to shoot 180 degrees. Most films shift to 90 to capture action without blur.

Yup, that is true. It would look more like a gopro shot then. Again it depends on the style of all the other shots. If he is just using off the shelf items I suspect its going to look a lot like go pro footage anyways. There was no indication of previous settings of the other shots.

Wow broad question, do you have anything to narrow it down, only want wide, closeup, POV (from front or back), moving with the actor etc.
what is the context of the film or story does it need the shots (Storyboard)
If it was me, using a wheelchair could produce some nice shots from behind, if it is on a road/street you could film out the back of a cars boot or pickup (consult H&S first), We did some shots like this of a car behind us and someone running behind a car being chased
could go really simple and just have the rider scoot across the screen (left to right / right to left) without panning and static on a tripod, or the rider could ride up to you ans pass you as you follow through (handheld or tripod)
{EDIT}
beg, borrow some go-pros and mount them in all places to get some action shots
SOOOO many options depending on what you want out of it in the end, good to have a storyboard of basic visuals first then work off those


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Battlestar Galactica Style Lens Flare?
How are lens flares akin to that in shows like Battlestar Galactica, SGU, etc. achieved?
Here is an example:

I think the type of lens flare you're looking for is anamorphic lens flare.

Best to do it with a real anamorphic lens, but those are crazy expensive, and I hear diopters are a PITA to focus.

Ah, yes, that's exactly what I'm looking for! Thanks!

All the main editing packages have lens flare as an option, so this is incredibly easy in post.
To do it live is less controllable, but is still simple - in fact avoiding lens flare is one of the challenges, as many lens configurations give unpleasant flare when shooting anywhere near the sun.

If you have an editing package, you can see if any of the popular lens flare plug-ins are available for it. For example:
mFlare
Knoll Light Factory
I know that Motion has a built-in lens flare generator. I'd assume most other packages do, too.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

sort: votes


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Can I use h.264 codec inside .mp4 container for my website
I would like to use h.264 as the codec inside .mp4 container for my user uploaded videos for my website. But I saw somewhere that h.264 is non free. I am unsure whether I can use this technology or not. My question whether I can use it to compress my user uploaded videos in my website? If yes, then its great. And if no, what other solution can I go with? Thank you.

You are correct: h.264 is non-free and content producers as well as developers are obliged to pay royalties to MPEGLA for its use - but only if they are charging for their content, and the volume goes over the threshold MPEGLA sets (which is in the order of 100,000 paying subscribers or > 12 minutes in length if charging title-by-title). Thjey have also said that they will never charge for h.264 video that is freely distributed.
See MP4 / h.264 patent issues?
for more info.
TL;DR if your video is free to view, then h.264 is free for you to use, and as @LordNeckbeard points out, it's a ripper of a codec, so knock yourself out.

Just to be more clear, it will be a video sharing website like keek or youtube, and I won't take any fees from the users, just will show ads. Therefore just to be on the safer side, following your answer, I don't have to pay even if my users are more that 100,000 right?

Remember rhat my legal advice is worth all the money you're paying me. To be "on the safer side" I'd get a lawyer once your user base > 100,000. But there's links to the MPEGLA terms in the other question I mentioned, if you want to judge for yourself.

Yeah, I've seen people ask before if making money from adds still counts as free.  The consensus on the doom9.org thread was that it's fine, you only need to pay the MPEG-LA if you're requiring money for content.  (So I think even free but donation-supported would be ok.)

Use it. Nothing else can provide the the same quality per bitrate as x264 (the top-class H.264 encoder) while not taking 10,000 years to encode (x265 'n VP9).
Some tips:

Use a recent ffmpeg build since development is so active. Static builds are available and easy.
Add -movflags +faststart to your command. Once encoding is finished this option will relocate the moov atom to the beginning of the file allowing playback to begin for your viewer before the file is completely downloaded.
Because ffmpeg attempts to avoid chroma subsampling using -pix_fmt yuv420p is recommended to ensure a widely compatible pixel format.
Some devices may require you to use a more restrictive profile and level. You can do this with the -profile:v and -level options. Be aware of attempting to force a specific level on outputs that will not conform (such as trying to force -level 3 on a 1920x1080 video). ffmpeg will give level limit warnings in the console output if this is the case.
See the H.264 and AAC encoding guides for more info.

Very informative! Thank you. I can't accept the answer as it does not state much regarding my question, but I have vote your answer. Thank you again for such an informative answer!

VP9 does required 10,000 years to encode , while x265 able to do mealtime encoding even on my weak VPS for SD format which is impossible with VP9

@SalemF Looks like x265 may have gotten faster since this answer was written. I'll have to give it a try and maybe update this answer. Now there is an even slower newcomer, AV1, which when stable will put the others to shame in this slow race.

Offtopic can you take look at my question here as it on of HEVC downside it's harder to create live broadcast using current tools 'that's mostly support H264 with FLV container'

If I am right, HTML5 supports H.264 codec with mp4 container. In this case the company which developed the browser has paid it's license.
You can also use video servers for VOD playing, like Wowza Streaming Engine.

That's not true. Although the software has paid a license, if you are charging viewers for the content and you go above the threshold for number of subscribers you owe MPEGLA royalty fees for using the codec.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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How can I save the project for premiere cs 5.5?
I edited a project in Premiere CC and my client owns Premiere CS 5.5, how can I save the project file so he can use it too?

Short answer: You can't. Unfortunately, there is no way to save a project so that it can be used in older versions of the program. That's a major downside of Premiere Pro, especially since this is possible with most other programs of the Adobe Creative Cloud (InDesign, Illustrator, Photoshop, ...). But at the moment, you can't do that with Premiere Pro.
You could use EDL files (Editing decision list). From Wikipedia:

An edit decision list or EDL is used in the post-production process of
  film editing and video editing. The list contains an ordered list of
  reel and timecode data representing where each video clip can be
  obtained in order to conform the final cut.

However, only the order and timecodes of the clips in your sequence will be carried over. All effects and other settings you already put in place will be lost.


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How to animate the outlines of text (After Effects)
Is there a method in After Effects of animating the outlines of text as seen in the example below?

This question is relevant: http://video.stackexchange.com/q/14592/2178

Simplest way is to use the Stroke Effect on a solid layer with separate letters as masks.

Create a new solid
Write your text in Illustrator
Convert it to a path
Separate all letters  with the path finder or ungroup it
Setup same document size as in After Effects
Import your paths into after effects, pasting should also work with CTRL+V. Requirement is to have all of your paths from Illustrator as separate masks on the solid in After Effects.
Note: you can create separate paths from an image of letters within After Effects with the auto trace option (Layer > Auto Trace) - use black and white option and set it to the current frame (Note: Tracing letters isn't really accurate)
Apply the stroke effect to the solid layer which should be full of masks now
Tick All Masks option to make use of all masks
Set the paint style to transparent
Go to your first frame and set the End value of the effect to 0%
Click the stop watch of it to enable animation
Go to your last frame and set the End value to 100%

You can play with the settings of the effect, but in general this should do what you want to achieve.
Note: The order of masks determines the order of the animation. To reverse the effect simply duplicate the first keyframe and move it behind the second one.

This answer is brilliant, thanks a lot. I would however like each letter to be independent from another (so I followed the steps separately for each letter's outline). Also, I was hoping for it not to be a linear 0 to 100 stroke being drawn across the letter but instead continuous looping portions of the outline's strokes moving across the letter's outline. If the letter's outline was a train track the strokes would be several trains moving along it, with gaps in between.

@sstaccato Nice - to loop it you can write an expression for the end value with something like loop_out("cycle",0) or you can simply loop the composition, but to clarify that would be a new question :)

This process is mostly manual, but it shouldn't take long to accomplish.  I'll assume the background of your finished video is going to be a solid color, as it is in your example.

Create your text.  Make the "body" of each letter either transparent or matching the background color.  Add a stroke (outline) around all the text.  (This can be done in Photoshop; I'm not sure about After Effects.)
As a separate file, create a small circle or other shape that matches the background color.  (This can be done in Photoshop or even in MS Paint.)
In After Effects or Premiere, place your text.  Also place several instances of the small circles/shapes, which should be impossible to see unless they are over a text stroke.
Animate the small circles/shapes so they travel around the text strokes.

In After Effects,
-Create the text.
-Right-click on text > 'Create Shapes from Text'.
-Hide the fills of the shapes, unhide the stroke of the shapes.
-Expand the layer properties. Beside 'Contents,
click "Add: ►" > 'Trim Paths'.
-Playing with the 'Start', 'End', and 'Offset' properties.
that's all.


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Waving flag in After Effects from vector
Could anyone provide some insight on how to go about animating a vector flag (such as the one pictured below) to wave in the wind. Simultaneously, how could also animate what's "printed" on the flag to match? (Another example below). Thanks for any help.

The simplest way would be:

Create your flag in Illustrator
Think about or simply test how many frames/steps are key for animation
Draw your frames/steps on seperate Illustrator layers in to get the same position for all of it
Paste your frame/path with CTRL+V on 1 solid layer every 4-20 frames by switching between After Effects and Illustrator back and forth - time depends on your animation

Explanation: Through pasting the masks at a different time, After Effects automatically creates keyframes of the mask shape property. All copied shapes become interpolated keyframes like a roto shape animation to get soft transitions.
Note: The only limitation is that the number of anchor points per vector image should remains the same to get soft interpolation between the shape keys.

Thanks for the help. Ideally I'd wanted to do this in just After Effects and not frame by frame, but I realize it might not be possible.

@sstaccato You don't have to do it frame by frame... but you need a minimum of 4 I think. It's not possible to do this in ae - you need something like a wave modifier, but ae doesn't have a real 3d space to "simulate" something like this.

@sstaccato BTW: A upvote would be nice if this answer helped you to realize that this is not possible :)

I've drawn each "frame" of the waving flag in Illustrator but am having some difficulty applying each drawing as a keyframe in a solid layer. Where exactly do I paste the pen-tool drawn lines from Illustrator into After Effects? A photo/video would be helpful if it's not too much bother, otherwise I will upload a video of what I'm doing so you can see what's going wrong. Thanks again.

@sstaccato Please see the comment below your question.


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Acceptable to adjust colour levels dynamically
I am using Premiere Pro CS6 to produce a short film and have some questions about the levels video effect.
Is it generally considered good practice to make adjustments to the RGB levels throughout a clip? For example, I have a single take clip where the scene changes drastically over a few seconds from an environment with heavy reds to an environment with heavy greens and blues. Trying to even out the scope at only 1 of these points means that I'm clipping the highlights at the other unless I make some changes.
Obviously this is an extreme scenario but I'm thinking about perhaps scenes where a character walks across the shot wearing brightly coloured clothing that causes one or more channels to clip. Should you adjust the levels dynamically then or just set them so that they won't clip at the highest points so as to avoid strange color casts during that short period. Or should it even be more involved with something like rotoscoping to create a mask over the object and adjust that separately?
I know these are pretty loose examples but I'm just trying to avoid getting into bad practices if there's generally a right way to go about things like this.

What you're describing is color grading / color correction and yes, it's perfectly acceptable, almost mandatory for a good presentation. Usually it's done scene by scene, but it's not at all unusual to correct within a single shot, or even different areas within a shot.
To do it well you should explore a dedicated grading tool like DaVinci Resolve Lite.

Thanks for the confirmation. I've experimented with SpeedGrade but I don't find it that 'intuitive' so I'll investigate Resolve.

Just be aware of the $25K+ difference between Resolve (with hardware) and Resolve Lite (-:


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I have a TS file. How do I render it?
(I decided to post this here because it doesn't fit very well into the Gaming category, but it is a gaming question.)
I had the idea to try streaming video to Twitch one on computer and to record it with VLC on another, using Livestreamer. The result is a TS file.
If I wanted to upload it to YouTube, how would I convert it to mp4 (Or is there a better format?) without loosing quality?
Also, I hear people talk about rendering their video. I understand that when a video is first recorded it is in 'raw' format. What does rendering entail?

Post the output of mediainfo (https://mediaarea.net/en/MediaInfo, or apt-get install mediainfo on Debian/Ubuntu.)  The MPEG-TS container format can hold multiple different formats.  If it's just the same h.264 stream that your desktop encoded and sent to twitch (so there haven't been any lossy re-encode steps), and it's not too big a file to upload to youtube, then just upload it directly.  Or remux it to an mp4 container (without transcoding).  I assume there's a gui for this, if you don't have command-line MP4Box installed.

You can tell you're remuxing instead of transcoding because it goes as fast as a file copy, instead of at best a few times faster than realtime.

Here is the output: http://pastebin.com/5MRLNJY9

I've since realized, though, that the stream wasn't as HD as I thought. I do have one final question though: I read a while ago that sometimes video uses a technique to decrease size by 'chunking'? areas of the video. When the video moves a lot it then becomes all pixelated. What is this called?

ya that stream is weird.  H.264 Main (not high) profile, and 1088x576p30.  mp3 audio.  Does Vlc use a lot of CPU time while recording?  (It might be transcoding, instead of just saving the stream.)  If no, then that's what your twitch streaming setup is outputting.  And yeah, it should be fine to just upload it to youtube.  3500kb/s is a reasonable bitrate.

never heard of "chunking" in this context, unless you're talking about blocks / macroblocks.  Or possibly NAL units for streaming.  Or maybe slices for parallelism, instead of frame-level multithreading.

re: pixelation during movement.  This kind of artifact is called blocking.  You'll often see ringing ("detail" at edges that shouldn't be there), too.  This is what happens when an encoder doesn't have enough bits to spend to make the output look much like the input.  It's the same thing you get when you turn down the quality on a JPEG (the math is the same, they're both based on a DCT of blocks).  It happens during high motion because when the image is changing a lot, most blocks can't be encoded as "same as a block in the previous frame" (which saves a TON of space).

How do I fix it? Is this my PC's specs or a setting I need to configure?

Configure your streaming setup to use more CPU time and/or bandwidth for the video stream leaving your desktop.  Like always, video encoding trades off encode time vs. bitrate vs. distortion.  (assuming you're not decoding / encoding the video again when you record it, which would be introducing more distortion.)

"Raw" ususally refers to uncompressed video (though this is technically wrong), meaning you probably have a very large file. Rendering is the process of re-encoding the video using another codec, usually to reduce file-size while maintaining a decent enough video quality. The reason that .mp4-files with the H264-codec are widely used is that they offer a very good filesize-quality-ratio.
In your case, a very compressed file is not what you might want, since Youtube reencodes your video when you upload it. Every reencoding reduces the video quality, so the double reencoding will result in poor quality.
If you cant upload the .ts-file directly (I don't think Youtube allows this), you could reencode it to an mp4 or avi (imho, the latter is better in this case, though getting the encoding settings right is a bit tougher for beginners). The key is to chose a very high bitrate and the same framerate and resolution as the original video. Using a high bitrate, the quality-loss resulting from the reencoding can be minimized. However, this will result in very large files (espacially if you choose avi), which depending on your internet connection might take very long to upload.
There is a range of free encoding programs out there. I'd recommend XMedia-Recode, but you could also try Xilisoft Video Converter or Format Factory.
Edit: If you want to cut your video (i.e. add an intro and an outro, put different videos together, remove unwanted parts, ...), you'll need a video editing program. There are some freeware programs for this (none of which are as good as professional, paid programs), you can find a list of video editing software at wikipedia.

What bitrate do I use? The default in XMedia Recode is 2000. Is this sufficient?
Update: I used mp4, the result was higher quality but it's still not very HD. If you don't mind, I can upload the TS file somewhere today and see if you can help.

That depends on your original file. You can check it's bitrate with software like MediaInfo. To minimize quality loss, I would set the bitrate to roughly equal the original video's bitrate or slightly lower. Make sure to use a variable bitrate as well. If the resulting file is to big for you to upload, lower the bitrate before trying anything else.
If the bitrate is over 8000~10000 kb, don't use a bitrate that high for reencoding. Above that, you won't see much of a difference with gaming videos and the file would get really big ...

Assuming you want to use h.264 instead of next-gen VP9 or h.265, then you should use x264, or a GUI that uses libx264.  mediainfo on the resulting file will show that it was encoded with x264, if you aren't sure what a GUI uses.  You can trade off more CPU time for smaller files with the same quality by using --preset slower, or even --preset veryslow.  For rate-control, you might want to use CRF 20 or so, rather than a target bitrate.  A given CRF will give you similar quality for all inputs, and the output bitrate will vary depending on how compressible it was.

If I wanted to upload it to YouTube, you neeed convert ts video to webm mp4 first,  total video converter is a converter transcoding .. avhcd mts ts file to mp4 with raw quality.


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What are ways to show phone conversations?
Suppose you have person A in one room, placing a phone call to person B in another room. How would you show the resulting phone conversation?
I can think of two ways: One is to split the screen, so person A is shown on the left side, and person B on the right side.
The other way, is to have alternating "full shots" switching back and forth between persons A and B.
What are these video techniques called? Are there other techniques that I've overlooked?

The technique of intercutting two scenes in different locations is called 'Parallel Editing'. http://is.gd/C9x55l

I like to think of alternate ways to do things, so here are a few.

One variation of the split screen is a picture-in-picture layout, where Caller B is in a small (often rectangular) box overlaid on the main shot of Caller A.
Another variation of the split screen is a "cloudy" picture-in-picture, where Caller B appears as a cloud-shaped image with fuzzy edges overlaid on the main shot of Caller A, usually floating above Caller A's head. This is sometimes used to make it look as though Person A is thinking of Person B, but I'm pretty sure I've seen it as a phone call too.
If the call occurs in present day, a video call on a computer screen can show Caller A and Caller B in a variety of layouts.  It could even include Callers C, D, E, etc.
Some scenes only show Caller A, and Caller B is heard without being seen.
In the movie The Player, there is a creepy scene in which Tim Robbins calls a woman he's attracted to / stalking.  He's on his cell phone, outside of her house, at night. She can't see him but he is looking in through her windows while they talk. So there are some 2-shots that show both of them on the phone simultaneously. (It's briefly included in the trailer at 1:10.)


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3D layers not affected by camera zoom in After Effects
The composition I'm working with has a 3D object I created in Cinema 4D Lite, as well as another layer which is controlled in After Effects (the content on the screen):

When I zoom in using the Camera layer the only thing affected by the zoom is the layer in After Effects, and the 3D layers stay in place.
Normal zoom:

Increased zoom:

Is there a way that I can zoom in/out of the entire composition, including the 3D layer? I'd like to begin zoomed in entirely on the screen, and at one point zoom out and make it apparent that it's all taking place on the computer screen, which is 3D because it eventually rotates.
Thanks for any help.

In After Effects, make sure your Cineware effect on the Cinema4D track has the Project Settings --> Camera set to Comp Camera, as shown below:

This setting means that the camera in your After Effects comp will control the viewpoint of the object, instead of any camera in your Cinema 4D project (I think C4D creates a camera by default, even though you can't see it in the Objects panel, otherwise nothing would render).


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What software is available for recording in 1/60 FPS?

I am recording my computer screen which updates once a minute. I want to record for around 8-12 hours uninterrupted, and I would prefer not to compress the video because the details are very fine and any grainy pixelation would potentially make the video unreadable.
Is there any (preferably free) software I can use which records at 1/60fps and can output a lossless (or very close to that) format?

OBS is what I use to record my screen. It is mainly for streaming to websites like twitch but they put a functionality of recording the stream as its going that records in lossless. Also you don't need to be streaming to record. Better than any program I have ever used, it's free, and you can change the frame rate!

Note: look up on YouTube how to setup your desktop for capture

Can you select just a portion of the screen to capture, or does it have to be the whole screen?

@IDontWorkAtNASA It can record whatever part of the screen you want

AutoScreenRecorder (currently version 3.1) appears to allow you to record as low as 1 frame per minute in the Pro version only (the free version does not allow altering the framerate).

Fraps also allows you to record at any frame rate you want.
Though the free version has watermarks in its recordings.


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Handbrake CLI command not working
I am trying to get the HB CLI to run this command removing the framerate (as the default ATV2 is 30fps and in the UK that looks rubbish, I want it to use the source fps
./HandBrakeCLI -i DVD -o ~/Movies/movie.mp4 -e x264  -q 20.0 -a 1,1 -E faac,copy:ac3 -B 160,160 -6 dpl2,none -R Auto,Auto -D 0.0,0.0 --audio-copy-mask aac,ac3,dtshd,dts,mp3 --audio-fallback ffac3 -f mp4 -4 -X 1280 -Y 720 --loose-anamorphic --modulus 2 -m --x264-preset medium --h264-profile high --h264-level 3.1
This is the default I changed the Bold well removed it
./HandBrakeCLI -i DVD -o ~/Movies/movie.mp4 -e x264  -q 20.0 -r 30 --pfr  -a 1,1 -E faac,copy:ac3 -B 160,160 -6 dpl2,none -R Auto,Auto -D 0.0,0.0 --audio-copy-mask aac,ac3,dtshd,dts,mp3 --audio-fallback ffac3 -f mp4 -4 -X 1280 -Y 720 --loose-anamorphic --modulus 2 -m --x264-preset medium --h264-profile high --h264-level 3.1
but it doesn't seem to work, I don't know if I have missed something, any help would be useful

figured it out by the looks of it
{{{
   ./HandBrakeCLI -i DVD -o ~/Movies/movie.mp4 -e x264  -q 20.0 -a 1,1 -E faac,copy:ac3 -B 160,160 -6 dpl2,none -R Auto,Auto -D 0.0,0.0 --audio-copy-mask aac,ac3,dtshd,dts,mp3 --audio-fallback ffac3 -f mp4 -4  -4 -X 1280 -Y 720 --decomb --loose-anamorphic --modulus 2 -m --x264-preset medium --h264-profile high --h264-level 4.1
}}}
I was missing the {{{ }}} which there was nothing about in the manual unless I missed it


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What portion of m2t video file size is audio?
What portion of a video file is audio information? I have a large number of m2t video files where the audio is worthless to me. I'm curious if removing the audio portion from these files will notably decrease the file size. Could someone give me a ballpark estimate of how much this will decrease file size? For example, how much will a 5 GB m2t video file be reduced?

Not enough to bother re-encoding it - typically single figure %

You can check that with MediaInfo. It will tell you exactly how much space each stream (in your case, the video and the audio stream) of a video takes up and give both the absolute and the relative (i.e. percentage) value! To get the average proportions of the audio stream, just check a few of your videos and calculate ...

There are variables you don't mention, but you can make a quick estimate based on the video bit rate and the audio bit rate. With (say) 4800Kb/s video and 48Kb/s audio, the audio represents 1% of the file.


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How was this magic smoke animation done?
Hi I was hoping any experienced video producer could tell me how an animation like the one showing at ~0:29-0:50 on the left side of this video is done?:

and is it possible to convert such an animation to separate transparent .png frames?

If you want to do this from scratch you would need a software that has a particle simulation system. A popular tool for that is After Effects in conjunction with the plugin Particular from Red Giant. Its rather easy to use.
If you want even more realistic results you probably want to go with a more sophisticated solution often found in 3D packages like 3Ds Max, Cinema 4D or the the free and open source Blender.
If you dont want to render something yourself you can also buy stock-footage. A popular package is the Action Essentials 2 from Video Copilot. It offers pre-keyed (e.g. with transparency) footage from real smoke and fire and other misc. effects. You can easily colorize these to your liking and export them as a transparent png sequence.

Thanks a lot for the answer! do you think trapcode's form or particular is better to get a similar result? the action essentials 2 is a really cool option as well.

I'd say particular. Form is more for animating "surfaces", while in this case you can probably achieve similar results with form, you will have more freedom with Particular.

As Professor Sparkles pointed out, After Effects can generate smoke with its particle simulation.
Basically, you blur the particles and reduce their opacity and add shadowlets  (apparently requires Trapcode plugin) and lighting to make them look more volumetric.
Maybe you can nicely ask the makers of that video how they did it, because anything you create yourself might look much different, unless you know all parameters involved.
But then again, you probably shouldn't copy others' work.
You can generate smoke visuals with Blender (see e.g. this video) or other renderers with smoke/fluid simulation.
There are probably some costly dedicated generators out there, I guess
nVidia also has programming samples for its graphics cards, including one that generate smoke, so if you're a developer, you could take that, adapt it and record the output and import into AE.

After Effects has a built-in particle system. While its not exactly the most advanced one, you can certainly generate smoke.

Ok, thanks @ProfessorSparkles, so now I learned something interesting trying to answer.

Thanks a lot for the answer! do you think trapcode's form or particular is better to get a similar result? I am not looking to copy the creators work just want to learn how to create something similar. I might ask them how it was done though it's a pretty big company so I am not sure who I should refer to.


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Automatic motion blur in video editor?
Is there an alternative to the automatic motion blur in After Effects for Adobe Premiere, Sony Vegas or Final Cut?
I use it mainly to sync text/image animations with sound cues, however After Effects is not a real-time editor and is difficult to work with several layers.
Is this possible?

Google: RSMB (Real Smart Motion Blur)
I know it is available for after effects and Sony Vegas, not sure about final cut.
Note: It dramatically increases your render time, but it is definitely worth it

Thank you, I'm using it right now. Definitely a time saver!

The Answer is a bit short :) Could you please elaborate? Why I should use it?

@poor Short, yet appropriate to the question. I think the best way to see why it is the best out there is to look it up YouTube! :)

Motion from Apple has a setting for Motion Blur on all projects. This section of the documentation explains how to set it (in the project settings). (It's under "Motion Blur and Reflection Settings".)
Once the project setting is set, you may also need to turn it on in the canvas to see it while editing. See here for information on turning it on in the Canvas. (It's under the section named "Render pop-up menu.")
Motion renders a lot of stuff in real time, though turning on Motion Blur will slow it down. You can always set the number of samples to something low-ish (like 4 or 8) while working and turn it up for renders.
I believe that if you're using a Motion template in FCP that it will render the Motion Blur if you set the canvas to "Better Quality" playback.

Thank you, Motion is another vfx editor, I would to see this behavior in a standard real-time editor rather than a vfx package.


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Video in After Effects composition panel is pixelated during scrubbing
I am new to AE and following a Lynda.com essentials course.  In the course, the video in the composition panel stays sharp during scrubbing, as below:

But in my AE application, it shows as pixelated during scrubbing, as below:

My AE CC 2014.0 installation is brand new, without any configuration tweaks.  I am on Windows 8.1, using an Acer V5-571 laptop (i5).

It's because you're using Adaptive Resolution, where AE will attempt to let you scrub through quickly, by reducing the resolution it shows in the viewer.  Higher powered computers will be able to show higher resolution in the viewer more quickly.
There's an explanation in Adobe's help here:
https://helpx.adobe.com/after-effects/using/previewing.html
There are also many things you can do to adjust the quality of your preview, depending upon what you're working on.. For example, if you're checking the movement of something, maybe you don't need as high resolution an image but full frame rate... Whereas if you're checking the pixel-perfect quality of a matte, maybe you don't need as high frame rate during preview.
Also bear in mind that there are different render engines in AE now - if you're using the 3D raytrace renderer for 3D work, previews will be very slow unless using a super-fast machine.

Thank you, your answer led me to Preferences -> Previews -> Fast Previews, where I set the Adaptive Resolution Limit to 1/2 (was 1/8).  Now the rendering is much, much better.  I was disappointed to learn that my video card does not qualify for the GPU requirements, but there seems to be a widely used tweak for that, which I am going to try next.

By the way, I have no idea what 1/2 or 1/8 means and why the former is faster!

@Sabuncu For preview purposes you can set the resolution to 1/2 (half resolution), 1/4 (quarter resolution) and so on...

@poor Thanks. So half resolution yields faster results but better video? I am confused.

@Sabuncu Half resolution means faster caching to the ram (because of the lower image size) to faster preview the result of the animation with the ram preview.

@poor OK, now I understand - many thanks.

Just found it, might help someone else.
In the panel there are dropdowns in the bottom bar.
Change the drop down that says "quarter" (see 2nd images) to full (see first image).
That's it.


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GoPro Studio Editing HD Videos
Looking at buying a MacBook Pro with this Spec:-
2.2GHz Quad-core Intel Core i7, Turbo Boost up to 3.4GHz
16GB 1600MHz DDR3L SDRAM
256GB PCIe-based Flash Storage
Intel Iris Pro Graphics
Backlit Keyboard (British) & User's Guide (English)
Will this run the studio without any glitches etc etc. Thanks For your help Will

if this meets the minimum spec for the software then that would be your answer, reading the min spec it will be fine to run the software
Mac OS X 10.8 or later
Intel® Dual Core™
  Recommended: Intel Quad Core™ i7 or better
Any graphics card shipped with Intel® Dual Core™ Macs or better
Recommended for 4K editing and playback: Intel HD4000 or better
4GB
Minimum: 5400 RPM internal drive
Recommended: 7200 RPM drive.
If external, use Thunderbolt, USB 3.0, Firewire or eSATA
Version 7.6 or greater
if there is something more specific you would like to know we would need the specifics then

Thanks Adam. Looks like I will buy a Mac this weekend:-).

Obviously making sure the Apple Mac is the right choice for you of course. dont just buy one if you are not 1000% sure it is for you, going by the question the specs are fine and would be the same answer if it was a Windows PC as the specs are enough to cope with it all

Only other thing I would mention is getting a external HDD or two for working on and backup and the SSD will fill up quick with GoPro files


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Get effect to overcome image size [After Effects]
Quick question, how can I get a transition effect on an image (CC light wipe) to fill the composition?
Is there an easy way to do this?
Thanks
Using Adobe CC 2014

If you are applying the light wipe to an image which is smaller than your full comp size, then the light wipe effect will only fill the size of the image, not the full screen.
To overcome this, you could add a full screen solid behind your image, and pre comp the image and the solid.  Then add the light-wipe to the comp, not the individual images.
Alternatively, you could try putting an adjustment layer between your two images, and applying the light wipe to that.


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After affects transition help
I need to do a transition that puts random circles that expand over a video but each circle needs to start at random times.
Does anyone know the best way to achieve this?

Do these circles act as a wipe between two full screen images, or do they contain individual images, or...? Does each circle cover only a portion of the screen, or would each eventually expand to cover the whole screen? Details, please -- maybe a drawing?

Two full screen images

I apologize Jim, I was checking on my phone and only saw half of your comment. Yes, it is two full screen images. Each circle only needs to grow to a certain size say 75 pixels but there needs to be enough to fill the screen at the end of the transition.

You could use the particle engine CC Particle World.
Set the particles to be shaded spheres, adjust the X&Y radius of the producer to fill the screen, adjust the birth rate to produce particles at the rate you need, turn off gravity and velocity.  set the end size to be so big that they fill the screen.  Set the Particle Transfer Mode to "black matte", and you'll get something like this:

then precomp the particle layer, moving everything inside the comp
Now add your two layers (the files for before & after the transition). Put the "before" layer at the bottom, then the "after" layer, then the "particle" comp layer.
Turn of the particle layer by clicking the eyeball.
In the example below, I'm using a pink and blue layer for the before and after.
Add a "Set Matte" to the "after" layer, and set the "Take matte from layer" setting to your particle layer.
When you drag through the comp, your "before" layer should reveal the "after" layer via your circles.

That sound perfect i will try this asap. Thanks tomh. This takes me back to my days of playing with particles in Lightwave 3d.

One way to do this would be to construct a matte layer out of white circles expanding as needed, then key one video layer over the other using the matte to reveal. You can animate graphic circles for the matte, as many as you like.

Thanks Jim, this is similar to what I was expecting but can you point me in the direction of how to create the matte? In my tests so far, I have created each circle on a seperate layer however this will be ridiculous to have to produce 100 or so layers

I'm not an AE maven so I can't give you specific directions, but there's likely a way to combine layers (mix down or render) each time you add, say, four layers. Then when you're done you have a single rendered layer you can import into your main project. Honestly, if I were doing this I'd write code (a script or similar) to create the circles but I'm not sure if AE can be scripted like that. Maybe someone else here knows.

There is. It's called pre-comping. It's been a while since I've done it, but if you check the docs for "pre comp" or "precompose" you should find more info.


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What means "Data: Skeleton" in an .ogv file?
My Question: I made a screencast with recordmydesktop (Version 0.3.8.1). When I investigate the rendered file with avprobe I see, that there is Stream #0.0: Data: skeleton in the produced file. I guess ffprobe will produce the same results...
What is "Data: Skeleton"? What is stored inside such a stream? Is it necessary to play the media file?
What I did: First I record a part of my screen via
recordmydesktop --height 10 --width 10 -y 50
Now I run avprobe out.ogv an I get as a result
avprobe version 9.16-6:9.16-0ubuntu0.14.04.1, Copyright (c) 2007-2014 the Libav developers
  built on Aug 10 2014 18:19:26 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
[ogg @ 0x93aa700] Multiple fisbone for the same stream is not implemented. Update your Libav version to the newest one from Git. If the problem still occurs, it means that your file has a feature which has not been implemented.
[ogg @ 0x93aa700] 22 bytes of comment header remain
[ogg @ 0x93aa700] truncated comment header, 1 comments not found
[ogg @ 0x93aa700] max_analyze_duration reached
Input #0, ogg, from 'out.ogv':
  Duration: 00:00:06.93, start: 0.000000, bitrate: 9 kb/s
    Stream #0.0: Data: skeleton
    Stream #0.1: Video: theora, yuv420p, 16x16 [PAR 1:1 DAR 1:1], 15 tbn, 15 tbc
    Stream #0.2: Audio: vorbis, 22050 Hz, mono, fltp, 89 kb/s
Unsupported codec with id 0 for input stream 0

When you want to investigate the video file by yourself, you can download it at http://www38.zippyshare.com/d/BaItXEdB/2145/out.ogv

What is Ogg Skeleton?
From Ogg Skeleton 4:

Ogg Skeleton provides structuring information for multitrack Ogg
  files. It is compatible with Ogg Theora and provides extra clues for
  synchronization and content negotiation such as language selection.
  The latest version of Skeleton, version 4.0, also provides keyframe
  indexes to enable optimal seeking over high-latency connections, such
  as the internet.

So basically the Ogg container can support multiple tracks of multiple track types types. However:

Ogg does not know anything about the content it carries and leaves it
  to the media mapping of each codec to declare and describe itself.
  There is no meta information available at the Ogg level about the
  content tracks encapsulated within an Ogg physical bitstream.

Ogg Skeleton attempts to deal with these issues by providing information about the other streams that allows parsing and (de)muxing without having to decode.
What is stored inside such a stream?

Ogg Skeleton is a logical bitstream within an Ogg stream that contains
  information about the other encapsulated logical bitstreams. For each
  logical bitstream it provides information such as its media type, and
  explains the way the granulepos field in Ogg pages is mapped to time.

See The "skeleton" meta information track for Ogg for more details.
Is it necessary to play the media file?
Continuing from the second quoted paragraph:

This is particularly a problem if you don't have all the decoder
  libraries available and just want to parse an Ogg file (such as with file)  to find out what type of data it encapsulates.

For playback you are decoding.
You're using (libogg/libvorbis/libtheora and) the FFmpeg cli tools (or should be; I don't recommend Libav) to demux and decode. You have the various decoder libraries available. You can download a recent build of ffmpeg.
Your file is not complicated. It just contains one video stream, one video stream, and one data stream (the Ogg Skeleton). It does not contain multiple streams of video, audio, subtitles, etc.
Ogg Skeleton 4.0 can index keyframes for seeking in high latency situations. Given the information you (did not) provide I'm going to assume this does not apply to you.

So the answer here is: Ogg Skeleton is not necessary to play this media file.
You can test this by remuxing the file while excluding the data stream with a negative mapping:
ffmpeg -i input.ogv -map 0 -map -0:d -c copy output.ogv

Now try playing it.


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Why does a bright video feed send more data than a dark one?
I've been watching the feed from a webcam (Foscam 8910).  When the scene is bright (lit with sunshine) the video feed is approx. 350 kBytes/sec.  When I view the same scene lit very dully with just a dim bulb, the feed comes at approx. 50 kBytes/sec.
As I understand it, the video feed only transmits the changes between frames.  Once the image has been transmitting for a few seconds, and there is no change whatsoever in the scene, the feed should settle down.
Why is there a seven fold difference in network traffic between light and dark scenes?  Shouldn't they be identical?

Based on neuhaus' comment, I've confirmed that the Foscam uses MJPEG compression.  Thus it's clear how a brighter (hence more detailed) scene would generate higher bit rates by repeatedly sending complete full frames.  I thought that it would be smarter than that.

Our eyes and brains are more sensitive to data in the bright areas so compression schemes generally throw out more of the data in the dark areas. If the video is mostly dark, then it compresses very well because they can throw out more data and you don't notice. But when it's bright (assuming it's not overexposed), less data can be crunched down without you noticing it.

Thanks for that, but I draw your attention to the 2nd paragraph.  I thought that a static image would generate much lower (virtually nothing) network traffic as nothing is changing between frames..?  Does video imaging not work this way?

It depends on the compression used. MJPEG compresses each frame individually for example.


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Color Temperature, Contrast, Brightness, and Saturation
How Can we measure each of these Parameters for 2 videos ? and the reason behind it is to make a comparison ?

Is it acceptable to split the video into frames and then compute these values for each? As a programmer, I would say that's totally doable.

Most prosumer-level (or higher) video editing software has monitor panels which show you information about color distribution, luminace, levels and the likes. Premiere Pro for example offers a range of reference monitors.
Contrary to photo editing, you can't get one measurement of those parameters for the entire video, because they of course vary from frame to frame (I guess you could calculate the average values, but that would be utterly useless). So you can't really compare two videos numerically accurate in that manner.

I can imagine a theoretical solution would be to analyse every frame of a video using these monitors, to come up with an 'overall' graph, but I've no guesses how to accomplish that.

But then again, what would that achieve? I mean with a photo you can use it to correct it, but with a video theres no way around looking at individual scenes and frames ...


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Transfer project from one application to another
As a beginner, I would like to know how important it is which software I decide to start out with. (Currently eyeing Adobe Premiere Elements and Sony Movie Studio 13).
I realize that whichever one I'll use, if I decide to switch application, I'll need to learn the other's interface and terminology. However, I was wondering about something else - Can I transfer a project from one to the other. Say I want to make a change to a video I created in one application, and obviously I don't want to input the created video (both because I lose resolution, and because I want each sound track separate etc.) - is it possible to transfer the video to other video editors, or will this project be "stuck" to this editor?

There are ways to transfer projects between different video editing programs, but they are very limited. Take a look at my answer here; this question is about transfering projects between different versions of Premiere Pro, but the answer is basically the same. You can export a project as an Edit Decision List (EDL), however this will only contain the arrangement of the clips in the timeline (namely your edit decisions, hence the name), any effects, e.g. color-grading, will be lost. Another format that does basically the same is AAF. I'm not sure about the differences between both formats, but either way, most of your post-production efforts will be lost when transfering the project to a different program.
Also, this applies to prosumer-/production-level software. I'm not sure whether "low-end" software supports importing and exporting EDL-files. If I remember correctly, it's not possible with Premiere Elements; don't know about the Sony programs (you should be able to find that out over the developer's websites and/or Google).


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After Effects: Parent a Camera's position to a Null-Object with specific Off-Set
I am just struggling with a simple expression thing I guess.
I have a camera looking at an Object in 3D Space. Actually The Object is at [0,0,0]. The Camera's position is at [29,-1637,-2248].
What I am trying to do is, to move the camera. For a better workflow I want to parent the camera's position to the position of a Null-Object, also at [0,0,0]. The thing is the camera has to keep its offset from [0,0,0] and just move parallel with the null at [0,0,0].
Can somebody help me?
Thanks in advance!

Welcome Slim :) If the camera is parented to the null with the pick whip correctly, you can move it as you like, what exactly is your issue? I'm confused :)

@poor thanks for your reply, the problem is, when I simply parent it with the pick whip, the camera copies the exact same position of the null. What I want is a specific offset to keep form the camera to the null object

This only happens if you use the expression pick whip. Try to use the standard pick whip here: https://cdn.tutsplus.com/ae/uploads/legacy/009_beginners2/25.JPG

To drive an animation by another layer use the pick whip or the selection list to parent it. In the following example the Camera (layer) adopts all animation properties of the Null.

Note: Camera is a 3d layer in your case, make sure 3d layer toggle is enabled for the Null too.


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How to get FFMPEG output the same quality as Vimeo?
I like Vimeo, but I rather host a player and video myself. So I was wondering if someone knows how to get the closest result to Vimeo quality, but from FFMPEG?
It seems that Vimeo uses 1280 pixels width for it's HD videos, but I'm wondering if there are presets or settings out in the wild that can specify bitrate, quality etc for FFMPEG?

ffmpeg example
tl;dr: The important options are -preset slow and -crf 20:
ffmpeg -i input -c:v libx264 -preset slow -crf 20 -vf format=yuv420p -c:a aac -ac 2 -movflags +faststart output.mp4

The other options are to ensure compatibility.

How to find out what Vimeo uses
1. Download video using youtube-dl:
youtube-dl https://vimeo.com/123456789

2. Get encoding info
Assuming x264 is used to encode, and the encoding settings weren't stripped out, you can see what version was used and view the encoding settings.
Using mediainfo
Refer to the "Encoding settings" line.
mediainfo input.mp4

Using strings (Linux or macOS)
strings input.mp4 | grep x264

Example output
x264 - core 157 r10 d4099dd - H.264/MPEG-4 AVC codec - Copyleft 2003-2019 - http://www.videolan.org/x264.html - options: cabac=1 ref=5 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=8 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=2 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=34 lookahead_threads=5 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 stitchable=1 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=2 b_bias=0 direct=3 weightb=1 open_gop=0 weightp=2 keyint=infinite keyint_min=23 scenecut=40 intra_refresh=0 rc_lookahead=50 rc=crf mbtree=1 crf=20.0 qcomp=0.60 qpmin=5 qpmax=69 qpstep=4 vbv_maxrate=5500 vbv_bufsize=15000 crf_max=0.0 nal_hrd=none filler=0 ip_ratio=1.40 aq=1:1.00

This shows that -preset slow and -crf 20 were used. The options are set by -preset, so there is no need to manually attempt to set each option.

VBV is enabled for streaming. In ffmpeg this is set with -maxrate 5500k and -bufsize 15000k. I just used the values shown in the encoding settings above.

Thanks to Vimeo for not stripping the SEI (they certainly could have like YouTube) and allowing us to see what they used. Perhaps they wanted to show that they appreciate the open source tools they use.

Also see

FFmpeg Wiki: H.264 Video Encoding Guide
FFmpeg Wiki: AAC Audio Encoding Guide

As always +1 for this very nice answer LordNeckbeard!


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What to make: a film, short film, series, web series?
I'm an independent indie film-maker with a strong ambition to advance onward, and I have no contracts whatsoever.
Is it better for me to create a feature film, short film, series, or a web series?
(This isn't exactly a question about opinions or one's thoughts.)
Which is more likely to be more successful, beneficiary, have a fan-base, and has a bigger revenue model, or which one is more valuable?
The thing I have in mind is a long story. Thus, I would perhaps want to eliminate the option of short film from my list.
How difficult is convincing a channel to broadcast a series with directors they do not know or have never heard of, or from another non-English speaking country.
Thanks.

One advantage to a web series is the absence of a gatekeeper. That is, you can upload (pretty much) anything you want to YouTube. You don't need to convince the website owner to include your work; you don't need to convince a TV station or movie studio to invest. In addition, sites like YouTube and Vimeo have built-in audiences.
To get a significant number of views, you would still need to do a lot of online promotion of your work by contacting bloggers, contacting "aggregation" sites that feature work like yours, posting on Twitter / Facebook / Reddit, and so forth.


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Premier Elements "Time Slider" in Premier Pro
I have just upgraded from Premier Elements to Premier Pr CC.
Premier Elements had a slider under the video playback area that allowed you to playback the video at different speeds or backwards. I found this really useful for looking for a certain bit in the video. It allowed you to quickly zoom to roughly the right bit of the video and then find the specific frame.
Does such a thing exist in Premier Pro? I've not been able to find it anywhere.
Thanks

The UI part you are looking for is called (depending on your locale, and local film industry) the shuttle, or jogger.
I don't know if Premiere supports the exact same graphical control.
However using the [J] [K] and [L] keys on your keyboard lets you:
[J] / [L] move backward / forward (moves fast for each press of the same button; moves slower in the same direction when pressing the opposite)
[K] Stops playback
Using these keys, you can shuttle around footage in the same manner as you previously used your mouse the the GUI interface.

OK, thanks. That sounds useful. I'll give it a try. I'll not mark this as the answer just yet to go others the chance in case this ui element does exist.


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After Effects: Create an isometric/orthographic Camera
I know that its not possible to create an non-perspective camera in after effects. But I read about a way to fake the effect of an isometric camera in after effects. I just didn't find something useful in the web so far so I wanted to post the Question about how to create an isometric camera in after effects here so you guys can share your ideas on how to realize this problem.
I just cant get over the fact that its not possible in a mighty program like After Effects.
Thanks for your sharing your opinions and ideas in advance!

Might be a better idea to use a 3d tool like blender, maybe related: http://www.blendernation.com/2015/02/09/behind-the-scenes-isometric-illusion/

Use a camera with a long focal length.  The longer the focal length, the closer to isometric.  Just back the camera far enough away to frame the shot.

works pretty well with a focal length of 50000 for me, thank you!

This might help, it's a script that creates an isometric camera view in After Effects
There's also a short blog post on how it's done which outlines the process:
Step 1. Add a new camera
Step 2. Change the camera settings:
Camera Position: 0,0,-5000
Zoom: 5000px

Step 3. Add a new null object, make it 3D and parent the camera to it
Step 4. Change the null object rotation to:
X Rotation: 35.264
Y Rotation: 35.264
Z Rotation: 35.264

Should get you close.

Can you summarize the contents of the blog post? Answers should really be able to stand on their own in case linked content becomes unavailable.


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I Finished My Film. How to Get It to Theatres?
We finally finished our amazing professional full-length film.
Whew! Long work.
The thing is everything was done by our team, as in no contracts with major companies, distributors, etc.
Are there any ways we can distribute our film to cinemas or stores? What are some steps to follow? Does a representative go to each theatre and present the film, or...?
Thank you.

What about monetized distribution on the internet?  I don't know how all of the rules work for sites like vimeo, but maybe you could find a distribution channel that would get A) money B) exposure and C) let you retain copyright.

It seems odd that you'd put in the time, money and effort needed for a 'professional' film with no idea what to do when you're done. In any case, one route would be through the festival circuit, where several successful films have found distributors. Your film needs exposure now, and you won't get it unless you explore every avenue.
And you will need a distributor: no significant theater or group will take on your film without one. An agent can help you get to distributors. It isn't unusual for a professionally produced film to spend almost as much on promotion and distribution as on initial production. If you can't afford it, you have to make a deal with someone who can.
At the very least you'll need to create a DCP (digital cinema package) and DVD screener copies for any festivals or agents you contact. Check the web sites of the major and minor festivals to see their submission requirements. Good luck.


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Why reencode MP4 to MOV for "easy post processing"?
On this page author reencodes MP4 from GoPro to MOV for "easy post processing". Why the processing becomes easier after that? The author also uses -sameq flag which is gone from ffmpeg without the explanation about what it did for H.264 blocks.

LordNeckbeard explained in his answer, why the given ffmpeg command line does not provide any known advantage.
But what - in general - could be reasons to transcode?

Available input codecs/containers of your NLE (video editing software)

There are hundreds of codec/container combinations out there, and maybe your NLE has just problems with the one that you have on your disk. Ex- and importing on different computers/NLEs/operating systems may introduce more unsupported combinations.

Playback speed on the timeline

This is about inter-frame vs. intra-frame codecs. The article "Inter-frame vs Intra-frame" has a short explanation:

Basically, inter-frame encoding [...] means that a video file contains sets of grouped frames that reference each other in order to produce an image. [...]
  Intra-frame compression means that each frame is individual and contains all of its own information. The file size will be bigger, but the computer doesn't have to look around to find what it needs.

  Examples of inter-frame codecs are the H.264/mpeg family, while Apple ProRes and Avid DNxHD are intra-frame. GoPro Cineform may also be an intra-frame codec, but I couldn't find enough info to verify it.

But to make it short, you only have to consider transcoding, if your playback speed on the timeline is not smooth.
Special filters that should be applied before working with the NLE

This may be the case, if you have some filters/effects that your transcoding software can apply, but not your NLE. Or your NLE sometimes forgets these effects.

In conclusion, there are some good reasons to transcode, but you should know, if they apply in your case and are worth the effort. Then choose a high quality intra-frame codec, but not mpeg.

Thanks. The playback speed is exactly the issue that I experience on Ubuntu 14.04 even without NLE.

There is AVC-intra, which could be considered part of the H.264 "family".

On this page author reencodes MP4 from GoPro to MOV for "easy post processing". Why the processing becomes easier after that?

The author provides no explanation and does not go into any detail of what he means by "post processing". What we know:

The author's ffmpeg command is using the encoder mpeg4 which will output MPEG-4 Part 2 video (like the old Xvid video).
The format of the GoPro video is probably H.264.

We must assume that the author believes H.264 is slower to decode than MPEG-4 Part 2 video, but that is not necessarily true. Or perhaps he believes that MOV container has some advantage over MP4 container when used with these formats; I can't guess what the supposed advantages would be since the containers are so similar.

The author also uses -sameq flag which is gone from ffmpeg without the explanation about what it did for H.264 blocks.

-sameq does not mean "same quality" (1)(2). The author's prodigious use of -sameq indicates that he doesn't really know what he is doing.
For H.264 specifically, when this option was still around (ages ago) it should have never been used when outputting H.264 because the option was designed for the "MPEG" quantizer scale which is not used by x264. Also, this option may have been ignored completely by libx264 at some time, but I can't recall exact details.

The format GoPro uses is H.264 - full meta is at http://video.stackexchange.com/questions/15196/detect-gopro-camera-model-from-mp4 and it is indeed very slow to decode on Ubuntu 14.04. I can't even watch the video.


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When nesting clip, how to make new sequence same resolution as clip instead of original sequence?
The scenario is this: I have a standard HD resolution sequence, which I drop a 4k clip into. Later I decide I want to use Warp Stabilizer on that clip in the sequence, but I get an error message saying I need to nest the 4k clip in order to use stabilizer.  The easiest thing to do then is right click the clip and choose Nest...
The problem is that the newly created nest sequence uses the resolution of the original sequence, instead of matching itself to the 4k clip resolution. This means the Warp Stabilizer still won't work.
I can get a nested 4k sequence manually with a lot of steps, but is there a better way to achieve what I want?

You can automatically create a sequence from a clip by right-clicking on it in the project panel and selecting "New Sequence From Clip". This will create a sequence matching the resolution and framerate of the clip and put the clip in it. You can drop the newly created sequence in your original sequence like any other asset in the project panel.

That will do for now, although it requires a few extra clicks going to the right clip in the Project Panel and dragging the new sequence into place. Adobe really needs to make that "Nest..." button configurable.


text:
Free Royalty Free Stock Footage
So I came across this website http://www.dissolve.com/ and they provide 3 free Royalty free stock footage every month.
I was wondering if there are any other websites where I can get Free Royalty free stock footage?

possible duplicate of Stock footage search service

Welcome to Video Production. You might want to try searching the answers that are already here before posting a question—there are already a few answered questions regarding stock footage that should help you.

There are several websites that do that. For example, this one accumulates free stock photos and there's also a video section. However, your best bet is to use a designated search engine like the creative commons search site, which will allow you to find material distributed under creative commons licenses. Before you use any of the found material, make sure to check which license it's using - some of them only allow non-commercial usage or require you to share any derivatives under the same license.


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Add path operation to multiple shape layers
I have multiple shape layers, and I want to add Wiggle Paths to all of them.
One way of course is to manually add to each of them.
Is there a way to add it to all of them at once? Specially is there a way to control them all in one place? so if I wanted to change the Wiggle parameters (like size, speed, correlation ...) I can change them all at once?

Thanks @poor . I didn't know you can add "path operations" to Null layers. let me try it.

Ah, I was also thinking I may find an effect to do the same thing

The only way is to drive your values by Slider Control's created on a Null, but this could take ca. 20min to setup.

I like the idea of a "slider control" why don't you put it as an answer so that I can accept it?

Use Expression Slider Controls to drive multiple Shape Layer Wiggle Path Values.
Here is an example of driving Size and Detail values of the Wiggle Path Property on 6 Shape Layers with 2 created Slider Controls on a seperate Null Layer:

Note: To save time, it's a good idea to create one shape layer first, set it up as described below and duplicate it afterwards to maintain the expression links.

Create a Shape Layer and a Null Object
Add Wiggle Path Property to the Shape Layer
Add a Slider Control to the Null for every value you need for animation (size, speed, correlation ...) and name it like these for a better organization
Select the Null and go to Effect > Expression Control > Slider Control
Open up the properties of the both layers by clicking on the small arrow  >  right beside the layer's name to see the values of the Wiggle Path and the newly created slider control at the same time
Holding down Alt while clicking on the stop watch of a Wiggle Path Value like the Size or Detail, this automatically will insert an expression
Use the expression pick whip and drag it onto the predefined Slider Control of the Null before to link/parent it, for e.g. the Size of Wiggle Paths, this should create something like: thisComp.layer("Name of the Null").effect("Size")("Name of Slider Control")
Repeat the process of parenting the Wiggle Path Values to the Sliders as long as all needed values are parented to slider controls correctly
If you duplicate the Shape Layer with CTRL+D now, all expressions will retained for the duplicated layers

@Ali Cleaned up the answer, added a screenshot and a gif for better understanding.


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Audio noise reduction: how does audacity compare to other options?
Audacity's noise reduction filter is pretty good.  Before I use it, though, I want to know if I'm missing out on any fundamentally different approaches that may work better.
I have some recordings of my brother singing and playing piano.  It's pretty good as-is, but there's noticeable white noise.  There's also a 60Hz signal that's audible (but not really objectionable) during quieter portions of the recording.  Audacity does a pretty good job of getting rid of them.  So I'll almost certainly just use that, esp. since very recent audacity changes apparently have improved the noise-reduction filter.  (or maybe just the config UI?  I didn't look at the diffs).
The comments at the start of the file describes the design pretty well, and what the settings sliders mean (esp. the frequency smoothing was a mystery until I thought to check the source, and found it had a great comment describing the design.)
It gets a profile of the kind of noise you want to remove from a clip of only noise.  For the main pass, it FFTs the input, and silences every frequency bin that is below a threshold.  So it's a bandpass filter that adapts to only let through frequencies with signals above the noise level for that bin.  (Thresholds established from the noise profile.)
So my question is, are there other designs for noise filters that work any better?  Mostly out of curiosity, since audacity works very well for my application.  (noise energy distributed over a wide frequency range, signal I want to keep made up of fairly narrow frequencies.)

I am the author of the code you are reading.  It appears you were an alpha user of Audacity 2.1.0 in advance of its release, which was only days ago.  You have a version of the noise reduction effect with many experimental optional controls exposed to the user that are not in the release version.
You may be interested in what I wrote here about the inadequacies of the previous version of the effect that I tried to remedy with this rewrite.  But the overall procedure remains unchanged.
http://wiki.audacityteam.org/wiki/Proposal_Noise_Removal#Critique_of_current_Audacity_Noise_Removal_by_Paul_Licameli

Thanks for that link, some of the discussion sheds some light on significantly different ways of doing noise reduction (i.e. not just different ways for choosing which FFT bins to pass/reject), as well as good info on how audacity's filter chooses which frequency bins to gate.  And the effect of choosing a good windowing function.  Lots of neat stuff. :)

After a bit of searching, I found an article surveying some of the commercial software noise reduction options.  For hiss/hum type noise removal (as opposed to crackles and pops), no approach other than noise-gates in multiple frequency bands was mentioned.  The differences between implementations are in the default settings, the control knobs available, and things like that.  (and whether the a noise sample is used to get a profile.  Apparently there are faster implementations that do well without needing a noise sample to build a tailored profile of the noise to remove.)
So AFAICT, Audacity's noise reduction plugin works the same way as commercial software implementations.
(For pops and crackles, Audacity allows making rectangular selections on the spectrum plot.  It might not have as sophisticated algorithms for filling in deleted glitches with similar-sounding audio from nearby, compared to some commercial software.  IDK, I haven't tried that.)
The other thing I was interested in was what's up with recent development activity in Audacity's Noise Reduction filter:
Following the svn history of NoiseReduction.cpp, there are really only changes to the GUI for setting parameters, from it's appearance in SVN r13591 (Nov 10, 2014) up to latest change in r13895 (Jan 24, 2015).
It replaces the over-optimistically-titled NoiseRemoval.cpp.  It appears to be a rewrite of the same basic design.  The intro comment describing the design is only slightly changed, and some of the same comments are kicking around in the code.  However, almost every line of code is different, and it's 1.9k lines of code instead of 870.
So it's probably not critical to get a pre-release build of Audacity 2.1 for noise removal.  If you get chimes / dropouts where you don't want them, or otherwise have problems, then go for a new version.  It looks at more data to decide if something is noise or not, as detailed below.
One critical part of the new filter now has several methods to choose from.  (OLD_METHOD_AVAILABLE is not enabled by default.  And DM_DEFAULT_METHOD = DM_SECOND_GREATEST)
(The code is well-commented.  I mostly just read the comments, on the assumption that the code matches well enough.)
//***** NoiseReduction.cpp:1079
// Return true iff the given band of the "center" window looks like noise.
// Examine the band in a few neighboring windows to decide.
inline
bool EffectNoiseReduction::Worker::Classify(const Statistics &statistics, int band)
{
   switch (mMethod) {
#ifdef OLD_METHOD_AVAILABLE
   case DM_OLD_METHOD:
      {
         float min = mQueue[0]->mSpectrums[band];
         for (int ii = 1; ii < mNWindowsToExamine; ++ii)
            min = std::min(min, mQueue[ii]->mSpectrums[band]);
         return min <= mOldSensitivityFactor * statistics.mNoiseThreshold[band];
      }
   // New methods suppose an exponential distribution of power values
   // in the noise; new sensitivity is meant to be log of probability
   // that noise strays above the threshold.  Call that probability
   // 1 - F.  The quantile function of an exponential distribution is
   // log (1 - F) * mean.  Thus simply multiply mean by sensitivity
   // to get the threshold.
   case DM_MEDIAN:
      // This method examines the window and all windows
      // that partly overlap it, and takes a median, to
      // avoid being fooled by up and down excursions into
      // either the mistake of classifying noise as not noise
      // (leaving a musical noise chime), or the opposite
      // (distorting the signal with a drop out).
      if (mNWindowsToExamine == 3)
         // No different from second greatest.
         goto secondGreatest;
      else if (mNWindowsToExamine == 5)
      {
         float greatest = 0.0, second = 0.0, third = 0.0;
         for (int ii = 0; ii < mNWindowsToExamine; ++ii) {
            const float power = mQueue[ii]->mSpectrums[band];
            if (power >= greatest)
               third = second, second = greatest, greatest = power;
            else if (power >= second)
               third = second, second = power;
            else if (power >= third)
               third = power;
         }
         return third <= mNewSensitivity * statistics.mMeans[band];
      }
      else {
         wxASSERT(false);
         return true;
      }
   secondGreatest:
   case DM_SECOND_GREATEST:
      {
         // This method just throws out the high outlier.  It
         // should be less prone to distortions and more prone to
         // chimes.
         float greatest = 0.0, second = 0.0;
         for (int ii = 0; ii < mNWindowsToExamine; ++ii) {
            const float power = mQueue[ii]->mSpectrums[band];
            if (power >= greatest)
               second = greatest, greatest = power;
            else if (power >= second)
               second = power;
         }
         return second <= mNewSensitivity * statistics.mMeans[band];
      }
   default:
      wxASSERT(false);
      return true;
   }
}

(why isn't syntax highlighting working?  I put <!-- language: lang-cpp --> before the code block :/)
I'm probably going to build audacity from this SVN checkout I already have, but I'm not planning to compare noise reduction between the latest dev build and the stable 2.0.6 release.


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Specify a custom "Movie rec. size" on Canon Rebel
Can you specify a custom "Movie rec. size" on Canon Rebel?
I have an SL1, and I'm trying to record at 1280x720 with 30fps.  When I go the "Menu" screen I see that you can set "Movie rec. size." It gives me four preset options. At 1080p, it records at 30fps and at 720p it records at 60fps, without an apparent ability to set them independently.
I do see however that changing the Video system to PAL takes it down to 50fps, but I'd like to stick with the NTSC standard of 30fps.
Is this possible? --to set a custom "movie rec size" on my Canon SL1 to 1280x720 with a fps of 30?
Thanks!

Short answer: no. The presets you get are what you are stuck with.
If you can do 1920x1080 at 30fps, it's easy enough to use a video editor or converter to go down to 1280x720 with minimal loss.
I frequently would record at 1080p on a Canon DSLR, and then finish and render at 720p (with the same framerate).

As a matter of fact, shooting at 1080p and scaling to 720p will make the image sharper, as well as saving some shots that were slightly slightly out of focus.

You need to turn the "wheel" located between the ISO button and the shutter release. There is an icon on the screen that looks like a rising sun.


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Combining high res photo with low res video in a static shot
Suppose I have a 1080p video of a static shot with minimal motion and little change in lighting, and a higher res (~ 18 megapixels) still photograph of the same setup.
How would I go best about using the extra resolution of the photo if I wanted an ever higher res video output (say, 4K)?
My naive idea would be to scale up the 1080p video in an AF composition and use a blending mode for it to influence the still photograph below. I'd have to do rotoscoping to isolate the moving parts and put them on top (upscaled)..
Is there a better way?

Welcome gohai :) Please start with the tour http://video.stackexchange.com/tour and add 2-3 images or frames to the question to get a solid answer, otherwise it's only guessing. Anyway, enjoy the site!

To extract the moving things, I'd try a difference matte. There's a tutorial on doing it in After Effects here and another one here. You'll need to somehow extract the static background, probably by averaging a few (or several) frames of it together. Then use the techniques described above to subtract out the static stuff from the moving stuff. (Maybe a combo of garbage mattes and difference matte could do it? Depends on the footage.)
Once you've done that, combining the moving matted footage over the hi-res image (probably using a "Normal" blend mode) should get you what you want. I'd be interested to know how it looks in the end. I've seen composites that looked bad because the composited object had a different amount or type of grain from the background. I suspect being at a different resolution may be just as bad, given that the grain will be huge compared with the background, but since I've never done it, I can't say for sure. Good luck!

Here are a couple of results using your proposed method. This was using a difference matte, and then putting the moving matted footage on-top using a "Normal" blend mode. I kept the settings for the Difference Matte pretty low, so almost every change in pixel values was made visible.
Example 1: a crop from a 1080p video scaled up to 4k using a photo and a difference matte
Example 1: the same, simply scaled up to 4k

Example 2: a crop from a 1080p video scaled up to 4k using a photo and a difference matte  -
Example 2: the same, simply scaled up to 4k  -
Example 2: a crop from the original 1080p video, but using a photo and a difference matte  -
Example 2: a crop from the original 1080p video, no changes

I'd be interested to hear your opinion. The lack in detail of the moving object is quite noticeable to my eye, but I am not sure if it's better or worse than e.g. upscaling. I was surprised to see the composed clip look better than the original even at the original video resolution of 1080p, even though this was shot as RAW video (there is probably an easy explanation for this). Any suggestions on how to make the matte method more seamless/intelligent?

My opinion is that the difference matted versions are much better, though I don't necessarily know the subject matter in the video you posted, so I may not be the best judge. The issues I was concerned with (grain matching, etc.) are probably more noticeable in typical narrative scenes. One thing that did stand out, though, was a difference in luminance and white balance. The difference matted versions seemed a little darker and cooler than the scaled up versions. Other than that, I think they look better, though.

It's an interesting idea, and I'd also like to see the results.
My first thought is that it would probably look very odd.  My feeling is that the eye is drawn to movement first, and detail second.
For instance, if your example is a locked-off interview shot, where everything is 4K resolution, except for the interesting part - e.g. the talking head, the viewer is barely going to notice that the background is higher quality, because all their attention is going to be drawn to the part of the image which is lower resolution.  Does that make any kind of sense?


text:
What happens when there is a "movie within a movie" or a "film within a film."
Suppose there is a movie set in early 1991, around the time of the Persian Gulf War. The camera pans on a film clip of President Bush declaring war on Iraq, and then a month later (in movie time), there is a another film clip of General Schwartzkopf reporting on the outcome.
What is this technique called and how is it effected?

It's usually just called "film-within-a-film," "movie-within-a-movie," "play-within-a-play," "play-within-a-movie," or whatever's most appropriate to the situation.  There's a french term which describes it (mise en abyme), but as an english speaker, it's often more practical just to describe the technique however it appears.  The Wikipedia entrance on story within a story gives many examples from film, theater, and literature.  The first example that comes to my mind is Nation's Pride, the film within Quentin Tarantino's Inglorious Basterds.  Personally, I would call Nation's Pride a film-within-a-film, and I think many other writers would too.

I like the French term, mise en abyme. Would that be any relation to "mise-en-scene"?

The similarity is that they both start with the French for "placed within". If you're fond of jargon, or you're writing in French, use the fancy French term, but if you like writing that communicates clearly I'd avoid it.


text:
vary the color of repeated shape in After Effects
I have a shape, in a shape layer, let's say a triangle. I apply a repeater to the shape, and I get lots of them. I can change the distance between them and their rotation ...
My question is: Is there a way to change their color? I mean to control what fill or stroke color each of the cloned ones have? either a random color or even specified color for each?

I don't think it's possible with repeater. You could do this with expressions and multiple duplicates of the shape however.
Here's an example I came up with:

And here's how I did it:

Firstly make your initial shape. Now duplicate that shape (with the shape selected hit
ctrl / ⌘+D). You should see this:

Note that we'll be making as many copies as we want later, but for the moment only make one, and get it set up so that we can duplicate it and not have to apply expressions to dozens of copies individually.
For each of the properties you want to alter with every repetition we'll add an Expression Control effect, as a handy way to be able to control the whole thing from a single slider.
Say we wanted to alter the position, scale and rotation: we'd add a Point Control effect to control position another for scale, and an Angle Control for rotation. Expression controls are in Effects>Expression Controls>

For ease of use rename each effect suitably. I've changed "Point Control" to "offset" and "scale ctrl", and changed "Angle Control" to "rotation":

We're going to add expressions to control the transform>Position property, the Transform>Rotation property and the Transform>Scale property of each shape object. Note that this is the property inside the shape, not the Transform properties for the layer.

In order to increment the rotation and scale etc. for each duplicate of the Polystar shape we have to find its index, or its serial number so to speak. With layers this is relatively easy, each layer has an index property, but shapes within a layer are layer sub-objects so we have to use a bit of magic to get the index of each. This thread is where I got the info I needed to work it out.
the key bit of the expression you need is this:
shapeIndex=thisProperty.propertyGroup(2).name.split(" ")[1]-1;
The variable shapeIndex now gives you a unique index for each duplicate that you create. This index can then drive the value of the various properties.

Skip this section if you're not interested in how it works
The expression propertyGroup(2) returns the string "Polystar 2" and we
  use javascript string function split() to split it on the space
  which returns an array ["Polystar", "2"].
  We select the second member
  of that array (or member[1], since javascript numbers arrays starting
  at 0) which returns "1". If javascript wasn't so sloppy with types we'd have to
  explicitly convert the string "1" into the integer 1, but it does the
  conversion without even being told. Yay Javascript!

So to add an offset to each duplicated shape layer we then use the shapeIndex variable and the expression control.
Firstly we'll add an expression to the shape's Transform>Position property. alt-click on the stopwatch next to the property to set an expression for that property. It will look like this:

Delete what is there by default and paste in the shapeIndex variable definition mentioned above:
shapeIndex=thisProperty.propertyGroup(2).name.split(" ")[1]-1;
hit return (not enter) to start a new line
Now use the pickwhip to get the value of the Expression Control Effect that we created for the offset:

Now we multiply that offset by the shapeIndex variable. The expression should now look like this:
shapeIndex=thisProperty.propertyGroup(2).name.split(" ")[1]-1;
effect("offset")("Point")*shapeIndex
So if your offset is [20, 20], then the fist duplicate will have an offset of [20,20], the next [20,20]*2 which is [40, 40], then [60, 60] and so on. You'll be able to change the value of this point control and have the duplicates update as you do it, without having to type any more code.
The same applies to rotation:
shapeIndex=thisProperty.propertyGroup(2).name.split(" ")[1]-1;
effect("rotation")("Angle")*shapeIndex;
And scale. Scale is a bit different because we want to increment the difference between 100 and the value of the controll - if the control is 110% we want to add 10% to the scale. And once we start adding vectors and scalars it gets more complicated - we have to unpack the array, and the integer and pack it up again. So we use this expression:
shapeIndex=thisProperty.propertyGroup(2).name.split(" ")[1]-1;
[100+ (effect("scale ctrl")("Point")[0]-100)*shapeIndex, 100+ (effect("scale ctrl")("Point")[1]-100)*shapeIndex];
If we only wanted uniform scale we could use a slider Expression Control effect, and the the same sort of expression we use for rotation:
shapeIndex=thisProperty.propertyGroup(2).name.split(" ")[1]-1;
(effect("scale ctrl")("Slider")/100)*shapeIndex;
Lastly we want to control the colour. Colour in AE is a four-element array [R, G, B, Alpha]. The individual components of the array are decimals from 0 to 1, where 1 is full on and 0 is off. So red is [1,0,0], yellow is [1,1,0] and mid grey is [0.5, 0.5, 0.5]. What you want to do with colour is up to you, but here's a demo. It fades out from red to green, with random variation on the blue channel.
Note that the shapeIndex definition in this expression is different. That's because the color property is nested down a level inside the fill property, so we have to use propertyGroup(3) instead of propertyGroup(2).
shapeIndex=thisProperty.propertyGroup(3).name.split(" ")[1]-1;
seedRandom(shapeIndex, timeless = true);
r=value[0]-shapeIndex/25.6;
g=value[1]+shapeIndex/25.6;
b=random()
[r , g, b, 255]
The seedRandom function creates a new, unchanging random number for each copy. If the timeless=true part is changed to timeless=false the random number will change with every frame. Another randomising function is the wiggle function, that softly changes values over time.
So now your shape layer should have two shape objects in it, and the second one will have expressions like this:

Here's where the magic happens
Now duplicate that second shape. If all goes well you should see new copies with offset, rotation and scale controlled by the expression control effects (make sure you have sane amounts for these values - the offset for example will default to half the width of the comp, which will move your duplicates out of sight. Try setting it to something like 50, 50 to start with). It should look something like the image at the start. Below is how the layer looks.

One of the cool things about doing it this way is that the expression is actually based on the name of the shape object. So the layer order doesn't matter. As you can see here, the copies are in front of the original, I can move them around so that they're behind, or individually move them up or down. Using the name is a little bit kludgy though. If I rename one of the shapes I might break all the expressions that control it.
If that's all too hard to read, here's the project

+1 for this nice explaination, but you are right - a project file is nice to have. I've asked a meta post, how to share project files: http://meta.video.stackexchange.com/questions/1444/how-to-upload-project-files


text:
what are the elements of a lavaliere mic system?
I'd like to buy 4 lavaliere mics for my video recording, and I need some education about lav setups.
I imagine that wireless mics would be easier to manage, but they probably cost more. I imagine I would need the wireless mics, and a receiver for each.  I'd also need a 4-track digital recorder. Or does each lav mic include a digital recorder? Finally, I'd need a way to transfer the audio files to my computer as either MP3 or WAV files. (Synching them with video should be simple; I'll use a clapperboard.)

Most wireless lavalier microphones for video recording use are sold as single receiver + transmitter packages. I believe you can get receivers that take more than one input, but they are designed for AV production use (e.g. stage shows and so on) and are mains-powered and expensive. So if you want wireless you'll probably have to buy four transmitter + receiver sets. Wired microphones are certainly cheaper, but lapel mics and cables are problematic if your subjects want to move around. If they're not moving around, then maybe you don't need lapel mics.
Edit Someone has recently sent me a link to these Sony Bluetooth microphones, which look like a great low-budget option. You'd use them just like normal wireless transmitter / receiver units.
Audio recorders usually come with built-in microphones, but microphones don't usually come with recorders, if that makes sense. Given that digital recorders are fairly cheap these days it is tempting to use four recorders worn by each of the subjects with a wired Lavallier microphone, rather than four wireless sets, but the downside to that is that you can't set levels or monitor the input, so if there are problems you won't know until you get to the edit suite. And given that lapel mics are prone to such things as clothing noise or the subject accidentally hitting them you could end up with problems.
As far as your recorder goes, you could either get a four track recorder, such as a zoom H6, or a mixer to mix the four tracks into a stereo signal which then gets sent to a stereo recorder. Recording four discrete channels gives you the advantage of being able to re-mix the audio at a later date, and to edit around overlapping dialogue, but obviously it's going to cost more.
From the recorder transferring to the computer is trivial, most record onto CF cards or such like, and the recordings can be transferred via a card reader or often via USB. Synching is also easy, even without the clapper board: editing software such as Final Cut Pro X and Adobe Premiere can synch audio tracks automatically.

Thanks for all this info! From your second paragraph, it sounds as though I could buy 4 small, lightweight, digital recorders, each with its own wired, lapel-clip (lavalier) mic. Is that right? If so, that sounds like a great solution! (Either that or 4 digital recorders with WIRELESS lapel-clip mics.)

I don't know of digital recorders that come with lapel mics built in. You'd have to buy the recorder and mics separately. It's certainly one way of doing it, but bear in mind the caveats I mentioned.
If you were to get four wireless mics, why not a four track recorder? Cheaper, and you don't have to press record four times each time you do a take.

Great advice. Thanks @stib! I'll just have to make sure the recorder can output each track as a separate digital audio file, so I can mix them separately.


text:
Simple video animation for teaching purpose
I am teacher , I am teaching web technologies and programming languages ,sometimes i need explain some technologies by some animation .
here is an example https://vimeo.com/113530912
i wants know what techniques used in this like video and what best way to start.

In the example given, motion graphics techniques are used. Motion graphics consists of Graphic Design and Animation, of course. In order to create something like that, you need a tool which includes typography, color and animation features, but actually it's key to handle and process all of your design assets, like flow charts, icons, images or backdrops, which created in other applications with animation in mind.
In general you can do this in many 2D animation tools, but In terms of flexibility and speed, I suggest you to use Adobe After Effects in combination with Illustrator or Photoshop. Almost every image and vector format is supported, so in this you don't have to deal with technical limitations. Also It's layer based and for this reason easy to learn for this kind of animation work.


text:
Is there a program that can change monitor color temperature for lighting?
I'm shooting a scene for a film where the actor will be placed in front of a computer monitor. I want to use the monitor to light the actor, but I want to be able to adjust the color temperature to get the look I want. I have F.lux (https://justgetflux.com/), so I know changing monitor color temperature is possible, but I want to be able to control it. Preferably the program would be free, and I would be able to adjust the temperature in real time.

What do you want to show on the screen?

I was planning on using a white image fullscreen, and then being able to adjust the temperature from there.

You can use flux to set your monitor temperature manually ... also, what monitor are you using? Mostly all mordern monitors have in-built options to change color saturation, temperature, brightness ... or, even easier, couldn't you just use an orange/red/whatever-colored image in fullscreen mode?

I have an older AOC monitor, the settings on it aren't very in-depth. The main issue is I want to be able to adjust the temperature live so I can see what it looks like, which is why I want a program. I did look into f.lux settings a little more, and it allow some modification, but I'd like something a little more flexible if anyone knows of something like that.

Thanks for the other good answers. Here is what I ended up doing.
I created a blank white html page and made it fullscreen, and then used f.lux to adjust the color temperature. It worked for me, but I should point out to anyone looking to use this solution in the future that it isn't perfect. F.lux doesn't give a very broad range of color temperatures. They were enough for my purposes, but someone looking for a very warm or very cool look might not be satisfied. In addition, f.lux changes the color temperature for the entire desktop on all monitors, so if you have something color-sensitive running during the shoot, like using the computer as a monitor, your colors will be off on that as well.

If you can't adjust the monitor, then send it something other than pure white.
@poor already posted an answer to do this with Blender, but that seems like HUGE overkill.  I would have just booted Linux, logged in remotely, and done DISPLAY=:0 xsetroot -solid '#fff' to set a solid white background, or any other color I wanted.
And there's probably something you could run to open a fullscreen window with a color of your choice, to save the trouble of switching to a window manager that didn't clutter up the screen borders with stuff.  Maybe a screensaver type of program?
I can't think off the top of my head what would give you a GUI color adjuster that would change most of the screen in realtime.

Using a seperate OS seems even more overkill than installing a freeware program tbh

You could additionally mention that it's possible to boot it via usb stick.

@Gin-San: If it was a computer I owned, it would already be running Linux :P  Obviously go with whatever OS you already use.

Here is a hack. You can use Blender and the Blackbody Node of Cycles Render Engine. Following example shows a realtime viewport animation of the color temperature in kelvin:

Create some geometry (e.g. a plane) as light emitter
Setup an Emission shader
Create a Blackbody node and plug it into the Emission Color
Position your camera
Switch your Camera by pressing Numpad 0
Set the Viewport Shading to Rendered or press F12 to render the image

blend file

Renderings

2000K

4000K

6000K

Ya, good idea.  If you can't adjust the monitor, then send it something other than pure white.  Blender seems like HUGE overkill.  I would have just booted Linux, logged in remotely, and done DISPLAY=:0 xsetroot -solid '#fff' to set a solid white background.

@PeterCordes Thanks Peter. You are right, OP was asking to control it by kelvins and I thought Cycles is physically accurate and have an instant viewport interactivity/rendering, so it could work :) Why not converting your comment into an answer? I would like to upvote it ;)

sure, why not? :P