text:
Does the Sampling Rate affect the syncing process to a video source?
I have recorded interviews using a point and shoot camera for the video and my android phone with Smart Recorder. The camera records in MOV and is uncompress with mono audio. Then I use my smartphone to record myself and the interviewee, since the camera is far away to hear us. The audio is in .wav and I use Premiere Pro to align them. While it does work at the start, sometimes it magically gets out of sync all of the sudden, so I have to cut the audio so that I can catch up.
I am puzzled, and would like to have your insights on how to keep this at a minimum if possible, eliminate it. My theory is that sampling rate is an issue. If this is incorrect, please advice otherwise.

If it really does jump out of sync then it's not likely to be a rate issue, which would cause it to drift. But often, things may seem to jump out of sync simply because it suddenly becomes noticeable. As an experiment, get a clapper or similar and shoot it once every few seconds for the length of an ordinary interview. Does it truly jump out, or does it drift? That will help determine a solution.

@JimMack Thanks for the wonderful advice. I'll do that later.

You can tell which one gets out of synch like this:
Set up your camera and your phone like you usually do. Put a clock that shows seconds right in front of the camera. Then, even though this sounds boring, record yourself counting off the seconds.
Synchronize the video and audio in Premiere Pro like you usually do. When they get out of synch, check whether the video lost a second, or whether the audio lost a second. You should be able to tell based on the repetitive rhythm.
Then, as @AJHenderson pointed out, you should replace the piece of equipment that failed. I agree that a camera that can accept external audio input is probably the best option, though it's expensive.

I have another theory, since the phone I am using was thethering to my tablet is constantly uploading images to flickr at the time, delayed the audio recording for a bit.

Curious question: TV and Film producers usually record their audio separate from its source, and they are sync in the post. They are not directly plugging their mic at the camera, do they?

@MrA - AJ Henderson would probably answer this better, but if I recall from film school the answer is no - they're recorded on separate devices and synched in post production. I believe the advantage with a video camera is that when you plug in a mic, it synchs the audio with the video for you, and you also get the advantage of a good quality microphone placed near the sound source. (If these answers are helping, please give them an up-vote! Thanks.)

re: sep sound. This was the rule when shooting film, but is less common when shooting video. Modern video recorders have excellent sound tracks, easily as good as a Nagra. Even when sep sound is used, if the video recording medium can take sound, it's smart to feed it the same or compatible source to help later syncing, and for backup. And pros using sep sound will often use a common timecode recorded to all devices (or will sync device TCs between shots). But in any case, 'plugging a mic into the camera' is not pro practice -- there's always a mixer.

There are any number of possibilities, but the most likely ones all involve getting better equipment.  The most severe sync problems with phones tend to come from phones that use variable framerate video or tend to have cheap encoders that tend to drop or delay frames.
When you are recording video, each frame has to be recorded more or less in real time.  There is a slight buffer available to store frames while they are processed, but if images are not processed at the rate they are shot, then eventually that buffer fills.  If a phone can't keep up, it has two options, either drop a frame outright and skip to the next one or use a file format that lets it alter the frame rate on the fly and record fewer frames per second when it has trouble.
Both of these approaches often destroy any kind of audio sync.  The variable frame rate, if well implemented, should limit drift a bit more since the frames should still advance at a fairly consistent rate of time, but they may get delayed and become out of sync.  Dropped frames are generally far worse.  Since nothing exists for that frame, the next frame is simply used and a slice of time is lost in the video that isn't lost in a separate audio stream that didn't have the dropped frame.
Both of these problems are unfortunately hardware dependent and there is no way to fix them on the hardware you have.  (You could try to reduce resolution to make the job easier for the encoder I suppose.)  If one of these is the source of the issue, getting another camera with a better encoder is the only other option you really have available if you want to maintain the resolution you are using.
Another possible problem that is less common today, is that the internal timecode clock may simply be fast or slow.  For the most part frame timing is pretty consistent with modern technology, but if there is a problem, you can try syncing at the beginning and end of the video and adjust the audio speed accordingly.  Check a few times throughout the middle when you do this, because most modern problems will probably not be this simple and the middle will still be out of sync.
An even better solution is to use a camera that can accept an external audio input.  By syncing the audio to the video in real time while recording on the same device, you can ensure proper timing is maintained by the encoder.  It's still probably a good idea to do an external recording as well, since this will help detect if there were capture problems, but using an external audio input is far simpler than dealing with sync issues after the fact.

Thanks! But I am using my smartphone as a audio recording device and a point-and-shoot to record the video.

Ah, I misunderstood, but the answer is still relevant for the point and shoot situation too.  It does make it more likely towards the cheap encoder lagging and failing to keep good time code.  Audio recording is generally far easier and phones tend to have good clocks because they have to keep good time to communicate wirelessly well.  Point and shoots on the other hand usually add video as an afterthought and can often do marginal jobs at holding consistent timing (since it isn't needed for most consumer stuff.)

Interesting thought. You are suspecting the point-and-shoot as the cause of the syncing issue. I will keep that in mind and do the test from the other users and see.

A/V sync problems are noticeable at about +/- 0.1 sec.  The samplerate clock in your phone and camera would have to be exactly the same speed to within 0.1 sec over 10 mins, or however long your clips are, for you to be able align at only one point.
0.1 / (10 * 60) = .0001.  That's about 1 part in 10k.  Wikipedia says quartz clocks are often as good as 6 parts per million stability.  The stuff I skimmed in that and this indicate that it probably costs a bit extra to get the clock frequency that close out of the factory.  (and the 6ppm is the kind of long-term drift you can expect around the starting point, not the absolute accuracy of typical gear.)
Keep in mind, most cameras, esp. ones primarily made for still-image photography, don't need a clock as accurate as a wristwatch, so they probably don't have one.  Because that would cost extra.
I saw exactly this kind of drift between the audio from my Panasonic Lumix and audio recorded at the same time on a Dell laptop.  See Sync separate audio to video+bad-camera-audio, free NLE recommendations, where I describe a slow way to manually sync clips, and ask for a quicker automated way.
Anyway, this lack of clock sync didn't surprise me at all.  It's nothing to do with frame dropping, or bad quality gear.  It should work fine to assume that both clocks involved each run at a constant speed, just not at the SAME speed.  So you can correct a clip with a linear 2-parameter correction: offset + stretch.
I agree with AJ Henderson's suggestion that it's probably the camera's clock that's less likely to be right.  Phones have GPS receivers for timekeeping, and may or may not use that accurate timesource as the clock for their audio input samplerate.  And also as AJ points out, need to do wifi, which probably requires calibrated clock sources, unless they can just lock on to a received frequency.  Not sure how big a deal accurate clocks are with modern wifi modulations, but probably a big deal.
I would have expected issues recording on any two devices that don't derive their sample clock from the same timesource.  Until portable GPS receivers were available, movie studios had a master clock that distributed time to all A/V recording devices, so 1 real hour of footage from one camera would have exactly as many frames as 1 real hour of footage from another camera.


text:
Slowing down footage with easing (like iPhone 5s)
I have a 120 fps footage captured with a GoPro that I'd like to slow down with easing, like the slow motion playback functionality on iPhone 5s.
Is that possible without any extra plugins in Final Cut Pro X? I know how to slow down a footage, but I'd really like the effect from normal speed to slow motion.

You can do it by adding transitions between the speed changed clips as described in the documentation section titled Add Transitions Between Speed Segments. They say:

When two adjacent speed segments are set to play at different speeds, you can control how smoothly the video switches between the playback speeds. When there’s no transition between the segments, playback shifts suddenly from one speed to another. By adding a transition between the segments, you can create a more gradual, or ramped, effect. You can also control how quickly that transition takes place.

source: Stack Exchange

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

sort: votes


text:
What is a good wireless solution for video monitoring for BlackMagic Design Cinema Cameras?
We are looking for a video monitoring solution that is portable and used with the BlackMagic Design Camera. I found a link with devices that look great.
http://blog.vincentlaforet.com/mygear/monitoring-viewing/
Was wondering if any of you have experience with any of these devices. And if you have any other recommendations.
Thank you for all your help.

authors: Деян Добромиров

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


text:
Looking for free program that allows PiP, and cutting/splicing
I'm looking for a free program with no watermarks, that allows PiP, and cutting/splicing. Before you recommend VSDC, I don't like that because there's only sound on the preview, so to know when to add a PiP you would have to go back and forth between the preview and timeline. Also, you can't cut and splice from the timeline, you have to have another window opened to cut/splice. Oh, yeah, I tried Filelab, and it doesn't work, either.
So is there such a program that follows these rules? I hope there is. Thanks for reading.

Closely related... http://video.stackexchange.com/questions/2389/non-linear-video-editor-for-free-or-cheap-that-does-these-things

Also related... http://video.stackexchange.com/questions/2274/good-open-source-video-editors/

Every Mac comes with iMovie. Every PC comes with Windows Movie Maker.  Both of them do cutting & splicing. iMovie does one PIP at a time; you can't have more than one PIP onscreen simultaneously unless you do a workaround. I used iMovie for hundreds of short YouTube videos with LOTS of editing (and PIPs). I don't know whether Windows Movie Maker does PIP but I wouldn't be surprised if it did.
(edit)
Just Googled "Windows Movie Maker PIP" and found out there are free add-ins that do PIP. (At least there were for the Windows Vista version. I bet the current O.S. has add-ins as well!)

For $100 you can buy a very good video editor that can do everything on your list.
I recommend Sony Movie Studio.

Here's the rub: the cheaper the software the harder it is to do good work. Also asking for a 'easy learning curve' when it comes to a beginner editor is like asking for an easy time learning to play the organ. It ain't gonna happen. You may do better thinking about compositing with something like After Effects than with a full function editor. You may be able to find older versions of After Effects (anything around version 8 or 9, before the 'CS' series would work and can be found sometimes for less than $150). There are scads of online tutorials for this program.

Thanks @Craig. So After Effects can do multiple PiPs?

You can have as many PiPs as you can have layers in AE. Thousands, if you enough horsepower! All that you'd need, anyway.


text:
How can I adjust brightness when shooting high FPS video?
I've FujiFilm Finepix S8500. It is capable of shooting high FPS videos. It works fine in broad daylight but when indoors, the video is always dark. What settings I can adjust to make the video brighter? I tried to adjust ISO and aperture but that does nothing. I also notice that the videos are darker if FPS is higher. I understand why this happens but is there anything to get a brighter video?

Is there some restriction on using studio lighting?

I don't have that gear.

Its a great bridge camera, however it has a small sensor. Small sensor means it can capture less information on its sensor, even when setting a high ISO setting. Its strength is the great zoom, but the image quality is so so.

Two ways
1) Larger aperture (the lower the number the larger the aperture) letting in more light, but also narrowing your depth of field).
2)
I would suggest a higher ISO, don't understand why that does not work for you. The current crop of camera's now are absolutely amazing at capturing low light environments that you cannot see with the naked eye.
One of the best cameras for this is the Sony a7s, just released (s for sensitivity).
It needs to be seen to be believed.

Sony a7s high ISO video link

ISO 400,000...!!  Sure it started getting unusably noisy (even seen through the rather lossy h.264 encoding) around 1 million, but that's still absolutely insane.  Wish they had a link to a higher quality version that would actually let you see the noise levels clearly though.

Hmm, found a video that is a bit better, it looks like it is about 2 stops better low light than the 5D Mark iii and $1000 cheaper.  Not bad, particularly when you throw in slog2 4k HDMI output.  Sadly probably not going to have a RAW video hack any time soon though. :(

Yes, an amazing camera, a full frame sensor, amazing ISO. Here is one between Canon 5D and Sony a7s with HD 1080. It gets really grainy at 400k, I would probably stop around 100k ISO. For video cameras, I think this is now king of the hill. https://www.youtube.com/watch?v=wGr_hXgJVGs

Yeah, I shot my own video on my 5D at 25,600 to compare to the footage shot on the a7s that was online.  That's how I got the two stop level.  25,600 (max on the 5D3) is about the same noise level as 100,000 on the a7s.

The best way is to add more light, I see you mentioned not having the equipment to do so. There are a couple of home hacks to get around that.
1) Remove lamp shades and use the highest wattage bulb you can. I also prefer the clear glass bulbs sometimes with a diffuser over them. I find that tends to be brighter than the hazed bulbs but I have official evidence to prove this just experience.
2) This is my favorite home light hack... Go to home depot and buy your self the the double halogen work light with stand. These work great for video as they are bright, easy to move around, come with a rotating head and are on a stand already, not to mention the best part, they are cheap!
3) Use halogen track lights in the room. This is also a way to get a nice light array for not a ton of money. Again they are super bright, easy to move around, just mount the track to a piece of 2x4 and you have a mini light array right there.
Reasons not to use a higher ISO:
In all cases I avoid increasing the ISO unless absolutely necessary. A higher ISO will increase noise and there are no 2 ways about it. I always exhaust my other options first, aperture, exposure time and simply turning on a light if I can.

Be carefull with halogen lighting, you may get some frames brighter and some frames darker because of the light's frequency, you may be able to adjust that in your camera though. Mine allows to switch between 60Hz and 50Hz if my memory serves well.

Only with a larger aperture to let in more light if a higher ISO isn't helping. Though the camera probably already uses a very large aperture for this high frame rate mode.
The more FPS the less light per frame obviously.
Your only other option would be to adjust the brightness in post which is a very limited option as it increases noise and can introduce artifacts but it might improve the footage a little bit. This usually works better if you can shoot in MJPEG instead of h.264/AVC. Try to shoot with the highest bitrate possible to have the biggest flexibility in post.
Usually you want to shoot with plenty of light when filming with a high frame rate, especially in-doors.

Increasing ISO, if possible would be preferable to boosting brightness in post as it would minimize certain types of noise in the recorded signal.

Of course, any camera adjustment should be preferred over "fix it in post".

ISO was my first attempt to counter the problem but, like I said, it does nothing. Videos at ISO 100 and 12800 are equally dark. I think this camera ignores the ISO settings for video.
The problem is camera specific. It's not a DSLR.


text:
Bad video quality on 600D
I am a video amateur and have recently bought a Canon 600D, mostly for shooting. I have some photography background and the image quality of the 600D is far better than my old 350D, no problem with that.
But the video quality is simply horrible. I am not able to describe problems, but I saw smartphones with better video quality... It looks very bad, and the effect is more visible with low lights.
Here is two frames from my last shot :

Without mentioning the bad focusing and too high iso, anybody can provides some clues ?

Should be mentioned that the 600D isn't exactly the best DSLR for video out there. The artifacts that you are experiencing in your footage are the result of high compression. Check your video settings if you can increase the bitrate or choose a different codec other than h.264/AVC if Canon offers one by now for their DSLRs.
This thread might be interesting to read: http://forums.creativecow.net/thread/280/8433
Also a possibility would be to install Magic Lantern on your camera. This enables HDMI output which you could capture (will have a LOT better quality than h.264 encoded footage) and you should have more options about the video codec. On the Canon 5D Mark II they even enabled raw video capture to the CF card but I'm not sure if this is available for other models yet.
Though apparently you loose audio capture at the moment, which might be neglect-able as the audio capture on DSLRs is usually pretty bad. If you capture with HDMI then you can use an HDMI audio injector which aren't expensive so you don't end up with a separate audio and video file that you have to synchronize.

Ok, I've found the problem. I have tested with another lens (Sigma DG 70-300 f/4 - 5.6 Macro), and the result is much much better than with default lens. But I am not able to explain this.

Ah, you were using a kit lens.  That makes perfect sense.  Kit lenses are not known for their sharpness or clarity.  There is a reason it is a cheap lens that comes effectively free with your camera.  The reason it can be "better" on a smartphone is that the sensor is smaller and thus the optics don't have to gather as much light and are far simpler.

The Sigma DG is not a cheap lens too ?

And, by the way, do you know good and affordable wide angle lens ?

It is still relatively cheap, but it's also a third party.  Generally speaking, for the price, third party lenses tend to provide better optical quality until you get in to the really high end, at which point there simply often isn't a third party lens that meets the quality of the name brand.  A $150 Sigma is probably most comparable to a $300-$450 Canon lens.


text:
Merge MP4 with M4A
I have two files, one is MP4 file with video only and another is M4A audio file. What is the best and simpliest method of merging these two tracks in a single MP4 container? Is it possible to do this without transcoding (loosing quality)? Thanks!
Open source and free software is my preference.

Do they actually line up correctly or do you also need to synchronize them?  If it is synced, this is effectively a duplicate of http://video.stackexchange.com/questions/10730/combine-video-and-audio-ts-segments-coming-from-hls-stream/.  Different source for the streams, but same solution should work.

I wouldn't say its a 100% duplicate. While the answer works, there are also other tools specifically for MP4.
The question might help people that search specifically for MP4 merging.

Scratch that, tsMuxer only allows MP4 as input not as output.

ffmpeg looks promising. Might be worth a shot.
Specifically, the command
ffmpeg -i video.mp4 -i audio.m4a -acodec copy -vcodec copy output.mp4

should do the trick.

MP4muxer will do the job, it even takes raw h264 streams.
This process is usually called "muxing" and can be done with virtually any container format.
Of course audio and video has to have the exact same length to have synchronized audio and video.

If your output container can handle the relevant codecs, then you can simply copy both audio and video streams using ffmpeg:
ffmpeg -i video.mp4 -i audio.m4a -c copy output.mp4

Thanks, but how does it differs from the answer of the sgryzko?

It is simplified, yet provides the same resultant function.

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


text:
How to link an audio mp3 file created on soundcloud to your Youtube account
i want create a sound file on soundcloud and bring it to my youtube account.  How do i achieve this?

Download it from SoundCloud, add as the sound track to a video, upload it to Youtube.  Is there more to your question than this?  Are you simply asking how to add it as the sound track to a video?

You can link it in the description or if you are a youtube partner you can embed links in your video as annotations.

You may want to reupload the file to Youtube.
Convert the audio file (preferably your original, uncompressed file) to video with avconv -loop 1 -i cover.jpg -i original-track.wav -tune stillimage -r 1 -s 1280x720 -c:a flac -shortest -v error out-video.ogv (where cover.jpg is the still image you want to use for the video) or using a media converter like WinFF, and upload it to your youtube account.
You can place a link to the soundcloud page in your video description.


text:
HD PVR 2 GE, worth it, thoughts?
I am really trying to record/stream some footage from both computers and video consoles. The best solution wold be to use an Aver Media Capture Card, but seeing as that is out of reach financially, I was looking at the HD PVR 2. This allows for component and hdmi in with no delay pass through to a computer. Has anyone used this before, have any reviews or experience? How easy is it to get older systems on a 4:3 aspect ratio to work on it? I wouldn't think it would be too bad with the right adapter? Thanks for your thoughts.

I'm confused, looking online, I see the HD PVR 2 as more expensive than the Aver Media Capture Card.  Also, what do you have that is doing component video in 4:3 resolution?  Component (3 cables for video and 2 for audio) is NOT composite (1 cable for video and 2 for audio).

I am aware of that, but I was referring to older video game systems that don't have component capabilities. I've seen many adapters that upscale without aspect ratio modification. I should have elaborated more on why its out of reach, while it is near in price I would need an entire new computer to use it.

There are a plethora of capture cards on the market in that general price range from numerous manufacturers.  There are two main things to worry about with these devices.
First, for analog inputs, such as component video, you need to consider the quality of the analog to digital converters as well as what capabilities they have for scaling and format.  Not all converters can handle arbitrary analog resolutions (or digital for that matter).  You want the highest quality converters to digital you can get for the resolution you need.  For SD feeds, that may actually mean getting an older, cheaper device that has good converters, but doesn't support HD (and doesn't need as advanced of a hardware encoder.)
Second, once you have a digital signal, the quality of the hardware encoder matters greatly.  HD video is very, very large in raw data, so heavy compression has to be applied to store it and make it playable.  This compression is generally a complex and time-consuming process, but specialized hardware can allow for real-time encoding that can keep up with a live feed.  The quality of the encoder will directly impact the quality and size of the end video.
As far as comparing between one device and another, looking for reviews or video samples from each is probably your best bet.  As there are many devices out there, you are unlikely to find people who have used both and can compare them directly for you.  You might have more luck with finding people with first hand experience of popular devices like Matrox's MXO2 or BlackMagic Design's Intensity, but those are (slightly) more expensive professional devices.

Thanks for all of that information, ya I wasn't looking for any comparison really. Just wanted to know if anyone out there had used this device and if it was worth the money as a true capture card is not available at this time, due to computer limitations.

@Kyle - I'm not sure what you mean by "true capture card."  There is no reason a capture device has to be inside the computer.  An external device with hardware encoder is the same as an internal card, just a matter of how it hooks up.  As long as hardware encoding is being used, bandwidth requirements are significantly reduced.  USB 2.0 can be a limitation for some particularly high quality feeds, but firewire 800, thunderbolt and USB3 devices are just as good as card based solutions.

That is true, that's why I was looking at the device that I was. In the past I have tried cheaper dongles but they fail in too many ways to even justify the price.

Yeah, the hardware encoder is the important part.  Most dongles are just pass through devices with no encoder and leave the encoding task on the CPU itself.  It can work if you have a really, REALLY beefy rig, but hardware encoders are far superior (and more expensive).

Ya I don't believe this does any encoding itself, according to the spec sheet. But, it does have zero latency pass through.

@Kyle - the very first point under the Hardware specs for the HD PVR 2 is that it has hardware encoding.  Doesn't necessarily mean much about the quality of that encoder, but it does have a hardware encoder.  Generally any capture device over $100 should have a hardware encoder or you are getting ripped off.

Oh ya your right my fault, been looking at so many.


text:
Can modern cameras (BMCC, Red, Arri, etc) record to a drive over ad-hoc wifi?
Is there a solution that bifurcates drives and camera bodies?
At first glance it seems feasible that camera bodies could be equipped with 802.11ac mimo and transmit the raw image data to a drive at a DIT workstation.
Is there any tech hurdle in making this happen?

Any camera with an HDMI or SDI output can can stream via wifi using a Teradek Cube (http://teradek.com/pages/cube).
This setup will allow you to monitor and record via iOS or computer. It also supports remote recording over the internet (decoder needed).
In addition to WiFi, Terdek also supports 3G/4G/LTE cellular networks via a USB modem.

There is the Eyefi product line which basically wraps a small wifi chip together with a small arm SoC into an SD package with some limited internal storage.
http://www.eyefi.com/products/prox2
They do work but the range is rather limited and you have to use their software in order to use them. Also only SD cards in their product line which aren't used in most mid/high-end DSLRs.
The SPI bus used by SD cards makes this whole thing quite a lot easier than with the old CompacFlash interface. Though the CompacFlash interface can act as a small form factor version of the old P-ATA.
http://en.wikipedia.org/wiki/CompactFlash#Technical_details
In theory it's not all too hard to make and adapter with off the shelf parts, there is a huge discussion about this on this forum: http://www.magiclantern.fm/forum/index.php?topic=5470.350
It seems they never came to any solution but then again most of them are technology enthusiastic photographers. You will need some knowledge about electrical engineering to pull this off.
EDIT: Seems there are adapters for SD to CF:

Note that it does not stream data live, but rather allows remote access to the file after it is done writing.

I believe the main concern would be reliability of the connection and lag.  The potential buffering issues could be a concern based on being a generic data connection.
There are existing specialized solutions for sending uncompressed video data wirelessly though, so wireless data transmission is possible, wifi may not be the ideal technology to do it though.


text:
ffmpeg: Normalize audio in an avi file
Ι have an avi file that has different levels of audio. Is there a way to decrease and increase appropriately where needed the audio of my file using ffmpeg?

Compression is what is generally used to accomplish this kind of change in the dynamics of audio.  I am not familiar enough with FFMPEG to know if it has a built in compressor though.

You can use ffmpeg with the compand audio filter (a port of sox effect filter of same name) to "compress or expand the audio's dynamic range", but admittedly this is one of the more complicated audio filters.
Example from the documentation
Make music with both quiet and loud passages suitable for listening to in a noisy environment (whatever that means):
ffmpeg -i input -filter_complex \
"[0:a]compand=.3|.3:1|1:-90/-60|-60/-40|-40/-30|-20/-20:6:0:-90:0.2[audio]" \
-map 0:v -map "[audio]" -codec:v copy output

The video is stream copied (re-muxed) in this example since you probably don't want to touch the video.

Maybe I'm dense but when I try your example command I get "Output with label 'audio' does not exist in any defined filter graph, or was already used elsewhere." I guess [audio] needs to be something else? We have an AVI in OP's question which is the only file we're working with. Do we substitute an audio format, a bitrate, something else as a variable? I can't make any sense of this, even after reading the documentation. Any chance you could post a full working example for the file EXAMPLE.avi please?

@TomBrossman Can you provide a link to a pastebin of your command and the complete console output?

Sure, here it is.

@TomBrossman Change -af to -filter_complex, or remove [audio] and the maps. Also see the dynaudnorm filter mentioned by Paul. I think it's newer than this answer.

As AJ suggests, there may be ffmpeg commands to compress, but I suspect that in any case you'll need to separate the audio and video (demux), operate on the audio, and remux or re-encode. Ffmpeg, AviMux, and other tools can demux and remux most AVIs.
If there are defined sections with different levels, you can manually intervene using something like (free) Audacity to raise the levels of the quiet sections to match the louder ones. A final normalizing step, or even slight compression, could also help.

You can use FFmpeg to adjust the levels in your video files.
There is an answer on SU that explains how to do that: https://superuser.com/questions/323119/how-can-i-normalize-audio-using-ffmpeg

I sounds as if the OP has sections with different levels, in which case normalizing won't help since the relative volume of the sections won't change. A compressor would be the automated way to do it, but usually there's no good substitute for manual intervention.

True, I just skipped through the SU answer. It's indeed just about changing the volume.


text:
Output file longer than source with ffmpeg
I'm producing several versions of a clip (320x180 24 fps and aprox 2Mbps) compressed with h.264 with ffmpeg using Avanti. Each version has different framerate.
The video output has a slightly different duration than source:
source - 24 fps - 01:52
10 fps - 01:53
5 fps - 01:53
1 fps - 01:56
0.5 fps - 02:04

Results are the same if use Handbrake.
Why is this happening? I'm aware that there are several kind of frames in h.264, what is then ffmpeg doing when I set framerate? Is it setting keyframe interval?

How are you measuring the input and output durations? Also, without your actual ffmpeg commands and the complete console outputs it is impossible to provide an accurate answer.

I'm using Avanti, so I'm not sure of all the actual ffmpeg commands it uses internally, but I am only selecting codec, container, frame size, frame rate and bitrate.

I'm getting durations from player information and from how long does it actually take the player complete reproduction.

My best guess is that this is due to the length of a group of pictures.  h.264 streams are composed of 3 different types of frames.  I frames, which contain the full frame, P frames which contain the information that has changed since the previous frame and B frames which are bi-directional and contain information about the changes between previous and future frames.
These frames are used in a fixed order that is repeated.  That repeated set is known as a group of pictures.  Typical GOP lengths are generally somewhere around 15 frames.  At 15 or more FPS, you'll always finish your GOP within one second.  At half a frame per second though, it can take up to 7 seconds after your last normal frame for the GOP to finish.
That still doesn't seem to fully explain your 12 extra seconds, but it is possible you are using a longer GOP.  I can't think of any other potential causes.
It is also worth noting that under the hood, Handbrake is just a UI for other encoding libraries, one of which is FFMPEG, so that may also help explain the consistent behavior as well.

I don't know the mechanics of it (how ffmpeg handles it), but you can encode using a 'closed GOP' structure or an unclosed one. If you opt that every GOP is closed, the last GOP may be padded out to its native length. In some situations it's mandatory to end with a closed GOP, so this may be the default here.

I've realized that there is somewhat of "starting offset", i.e. video starts with black and there is a soft transition to an image of earth from space, if first non-black frame is aprox at 00:03 in source video, it does not appear until 00:23 in 0.5 fps version and its content come from a frame from 00:04. Maybe this confirms the "GOP-completness theory"... I will do more tests.

I've performed more tests and GOP size has apparently nothing to do whith my problem. I set -g 0 that, according to https://ffmpeg.org/ffmpeg.html (section 6. Tips), means an all I-frames video and keep getting extra seconds in output.

@jmm that's unfortunate. I'm out of other ideas.


text:
Record video and sound with backtrack
Here is my use case: I want to record myself (sound and video) when I play the trumpet to a backtrack.
Now if I didn't want the video I would simply:

record the backtrack with a DAW
record myself in another track while the DAW plays the backtrack

But I don't know how to add the video.
My guess is that I need either:

a DAW that also can record video stream (I have only a web cam for that)
to record with a video stream recorder, but I'm not sure how to add, play back, and sync the backtrack.
to record audio in my DAW, video in another program (movie maker?), and then sync audio and video with some kind of clap.

I am certainly not the first wanting to do that, the question is how can I achieve this? Other ways than the two above? Software recommendations?

This is really the same trick as what is needed for a music video.  There are two options for it.  If you want to record the actual performance, play the backtrack while recording the video and synchronize it after the fact.  You can either directly mic the instrument and play the backtrack aloud or you can use headphones or in-ear monitors to play the backtrack and split off a feed to go in to the camera for purposes of synchronization.
Alternately, you can do your audio recording completely separate from the video.  Record the audio in an ideal studio environment with clean trumpet while using headphones for the backtrack, produce the final audio and then playback the audio while recording the video.  This is the option that is generally closer to what a music video does and is what I would personally recommend for best overall quality.
In either case, you take the video track and the audio track (or tracks) and line them up after the fact in a traditional video NLE (non-linear editor).  You could accomplish it with something as basic as Windows Movie Maker, though personally, I'd use something like Adobe Premiere and maybe Audition for the audio (simply because Audition and Premiere integrate so nicely.)

So syncing by hand with some kind of movie clap?

Or a pulse put in to the audio being played back. If you add a metronome to the audio it is really easy to sync up.

Sorry for being thick, do you mean to sync an audio pulse that is both in the mix from the DAW, and in the audio attached to the video (audio which will eventually be discarded)?

Right, for recording the video, output from the DAW with a metronome attached.  Then sync the video to the audio using the metronome and replace the audio with the non-metronome version after syncing.

The thing is that audio and video need to be recorded at the same time.

@Gauthier - why do the audio and video need to be recorded at the same time?  It's fairly typical (more often than not) to record the video and audio separately for this kind of thing unless you are trying to record a particular performance.

This is exactly it, I want to record myself playing the trumpet, and I want the video to be of when I actually play the recorded sound. It's not a music video, it's for educational purposes, yet I would like good sound and sync.

@Gauthier - the same trick can still be applied, but it is more difficult to do so.  For best sync, I would recommend outputting the audio to headphones or in-ears so that you can get a clean recording of the trumpet.  Send a feed of the audio going to the headphones (with the metronome) to the camera as well so you have the audio pulses on the video.  Record the headphone mix to the left track and the trumpet to the right on a recorder like the H4n and you should be able to piece it back together.  The slightly less ideal case is to just insert a clapper sound at the beginning of the song.


text:
Add intro and outro to multiple files (batch)
I am fairly new to video editing but I have a ton of video files that I need to add an intro and outro to. I do a lot of other print work and in photoshop I can batch file folders to repeat the same action to all the files in the folder. I would imagine there is some way of adding the intro and outro in the same manner with a video editing program like Adobe After Effects so I can select the folder and automates all the adding and publishing. Is this possible with any system???

This is indeed possible with After Effects via its Scripting Interface, though this is a bit harder to use than Photoshop Actions. You will need to learn Adobe ExtendScript and how to use it in conjunction with After Effects.
For this particular job I'd suggest a different approach using FFmpeg. It's an open source video encoding and processing tool that is used for many video automation tasks in the industry.
You will have to write a script here aswell but that would be a LOT easier and shorter than digging into Adobe ExtendScript in conjunction with After Effects.
Assuming you have an rendered video of your intro, outro and main media file in the same codec. You can then use the concat command in ffmpeg to mux the three file into one, which results in a joined video without any re-encoding of the source media.
Here is a tutorial on how to do that in the Linux bash but you can do the same thing with AppleScript or Windows Batch script. You want to generate a filelist like shown in the tutorial:
file '/path/to/intro.mov'
file '/path/to/main.mov'
file '/path/to/outro.mov'

You would generate this filelist for every main media file and only change the path for your main media file for every "export".
Just for reference, this is the final command you would then use:
ffmpeg -f concat -i filelist.txt -c copy output.mov

How the script part looks that comes before the FFmpeg command that generates the file list, completely depends on your operating system and or choice of scripting language.
Note that you don't have to use the source codec, instead of doing copy you could also encode the output file into a different codec by specifying a codec with encode setting instead.
For example:
-c:v libx264 -preset medium -f mp4

This is also possible with AviSynth.  I recently built a tool that generates a quick AVI Synth script for a video file, an intro and an outro, encodes the newly created video and then uploads it to Youtube.  AviSynth has a bit of a learning curve, but if you have some basic development knowledge, it is pretty easy to get working.  Here is the script I generated out.
videoMTS="G:\terra\video projects\camera dump may 2014\00016.MTS"
ffindex(videoMTS)
videoFeed = Trim(Audiodub(FFvideosource(videoMTS, fpsnum=2997,fpsden=100), FFaudiosource(videoMTS)),120,1022)

vidWidth = Width(videoFeed)
vidHeight = Height(videoFeed)
vidFPS = FrameRate(videoFeed)

openImage=ImageSource("G:\terra\tool development\Proverbs---Opening-Picture.jpg", end=180, fps=vidFPS)
closeImage=ImageSource("G:\terra\tool development\Terra Nova - Closing Picture.jpg", end=180, fps=vidFPS)

BlankAudio=BlankClip(clip=videoFeed,length=180)

openImageAudio=AudioDub(openImage,BlankAudio)
closeImageAudio=AudioDub(closeImage,BlankAudio)

openImageSized=ConvertToYV12(BicubicResize(openImageAudio, vidWidth, vidHeight, 0.0, 0.75))
closeImageSized=ConvertToYV12(BicubicResize(closeImageAudio, vidWidth, vidHeight, 0.0, 0.75))

Dissolve(openImageSized,videoFeed,30)
Dissolve(last,closeImageSized,30)

It had a few tricks because I was working with an MTS file and two images, so I had to do some initial processing to make them work together.  They kay parts are getting the width and height and framerate of the main video, making sure it matches up with the clips being used as intro and outro and then scaling them appropriately.  I then add a dissolve for each with a 30 frame duration.
This just goes in a file with an avs extension and can then be opened by FFMPEG or most other encoders as long as AVISynth is properly installed.


text:
Actively Used and Developed Motion Capture Systems
I am looking for Motion Capture Systems that are actively used in the Movie Production Business.
I am currently aware of Organic Motion and it's OpenStage2 which can easily cost about 40.000$.
I would like to know if there are any alternatives that are either in the same Price-League or maybe cheaper. Most important is that it is indeed used and that it is actively developed.

We used the NaturalPoint OptiTrack S250e at my company for a big project that is still in active use today. We used it for a sort of game like exhibition on fairs. So it had to be quite robust and offer stable tracking in changing environments.
It is primarily used for movies and video games though. They offer quite a few different systems in price ranges far below your 40.000$ and far above that, depending on how many cameras you need and what precision you need. The prices are per camera.
They have a nice system configurator here, which makes choosing camera count and camera system a bit easier.
Some of their bigger customers can be found here. Seems like they have been proven in many bigger productions.
I have not affiliation with NaturalPoint and it's the only MotionTracking system I had contact with. There might be better solutions that I don't know of but we used their products and the result were satisfying for our special requirements.

I thank you a lot for pointing to this, this helps a lot. If it stays here as the only answer I will accept it of course.

We use a really old Vicon system, but according to the company's website, new ones start at $12,500.


text:
How to detect which part of the video is using copyright audio on facebook
I am having a issue i.e: Facebook deletes the video uploaded by me and says It contains copyright audio. It is 6min video so how could I know which part is being aborted by Facebook.
Thanks a million.

Are you using any copyrighted songs in your video?  This could be something as simple as playing in the background of a clip.

Not sure about Facebook, but I know that with youtube, there is an appeals process for when their algorithms detect copyrighted music when none exists.  Which leads me to the question; is Facebook actually hosting the video?  Because if so, you could just try a different host.

What @JasonConrad said is probably going to be your best solution. Facebook support is pretty much non-existant for things like this. Most of the algorithms are getting better but facebooks is probably the weakest still


text:
Image plane mark on Grass Valley Infinity
I'm working on a Grass Valley Infinity and for a specific application I need to know the image plane position (ie sensor position).
But I can't find the image plane mark like this :

So I have two question :

Is someone know any informations about this on the Grass Valley Infinity ?
Is there always an image plane mark on a camera ? I thought it was a "norm" for professional cameras.


text:
Premiere CS6 hanging on ExporterAVI.prm after an upgrade from Vista 64bit SP2 to Windows 7
How do I fix Premiere CS6 hanging on ExporterAVI.prm after an upgrade from Vista 64bit SP2 to Windows 7?  It hangs indefinitely but was working fine before the OS upgrade.  No unusual CPU usage or memory usage, it just sits there forever.

This is most likely related to an AVI codec not loading properly after the upgrade.  In my case, I had the Matrox VFW software codec installed.  Uninstalling it and installing the newest Windows 7 version fixed the problem.  Clean up your installed codecs and reinstall updated versions of the codecs you need and the problem should be resolved.

I had the same problem - Premiere hanging on ExportAVI plugin during launch. I have upgraded my NVidia display driver . . . and everything else runs fine on my Windows 10, desktop.  I think the ExportAVI.prm is a corrupt file . . .when I delete it, or move it temporarily to another folder, Premiere starts up fine. (the file is located in the Premiere/Plugins folder.)


text:
Avidemux "too short" error
I'm trying to encode clips with x264 in avidemux. Problems come when I set video length to 10 seconds while I resample output to 1 fps (without changing duration): avidemux report "Too short" error and produces an invalid file.
There is no problem if I resample to 2fps or if select a clip 20 seconds long. I have also tried different GOP settings with no luck.
Any idea of the reason of this error?

That is way out of the h264 specs. According to Adobe After Effects the format constrains for h264 are at min. 10fps so even 2fps are (not, see below) out of spec and could result in issues with some players. So Avidemux seems to allow out of spec settings, that 1 fps isn't possible, is very likely an internal issue with how h264 gets encoded in Avidemux.
Edit: It seems this is indeed an Adobe only constrain and or constrain for MP4, when using the QuickTime format with h264 I can render with 1 FPS.
Still, I recommend you interpolate your video to be longer instead of decreasing the FPS unless you have very specific technical reasons for encoding with 1 FPS.
Showing every frame multiple times per second instead of just once per second doesn't make a visual difference.

I have not read full H.264 specs thoroughly [link]https://www.itu.int/rec/T-REC-H.264/, but I cannot find a minimum fps restriction. I cannot find it in x264 or avidemux docummentation either. In fact, level 1.1 in H264 defines 7.5 fps as max frame rate for CIF resolution. I think 10 fps is a min value for Adobe implementation of the codec, not for the  the codec itself. I need a subsampled (in time) clip as if one image per second was captured which is different from "slow playback" in terms of information shown.

That of course could be the case, though usually the Adobe restrictions have a higher compatibility reason and are usually not a real technical limitation.
Though showing the first frame for 25 frames per second or for 1 doesn't make any difference, you will have it much easier by simply "interpolating", which in that case just means repeat every frame by X.

See my edit, its indeed an Adobe only constrain.

Thanks for checking and it is indeed interesting for me that QuickTime format allows 1fps rendering. I will give it a try altough I would need my videos playback supported in some standard browser. I didn't understood your interpolating suggestion, sorry, I had already tried it, but the clips have bitrate constraints, so again, I cannot interpolate for technical reasons since interpolating increases bitrate.

If done right it actually doesn't increase the bitrate all that much if at all, h264 is encoding based on differences per frame, set your keyframe interval to your FPS and you shouldn't see a lot of bitrate increase.
Look for example at a Youtube video that is just a music track with a still frame for like 4 minutes but its not larger than your average mp3 file because the video track is just a few kb in size, h264 is pretty smart and can be optimized for specific situations like these.

I know, but I am working with "ultra low" bitrates (5-25 kbps for video, no audio). I did several tests (changing GOP size and other settings) and didn't manage to keep bitrate and quality.

Let us continue this discussion in chat.


text:
Projecting slides on a large screen from 40 feet
I have a few small projectors for small rooms, but I'm finding that these do not work well for pushing light to a larger screen further from the point of projection.
In looking for possible upgrades, what key features do I need to evaluate in comparative shopping?  Is there a metric or feature I need to look for in a projector that will allow it to throw a bright, clear video projection from further away?  To clarify, I'm not needing to replicate what the local cinema's use - I'm only showing slides not video content.

You'd probably want to look for the following characteristics:

Min and max projection distance (from the data sheet, make sure the projector can focus correctly for the desired distance)
Lumen (some people recommend 500 lumen per square meter projection area, but of course, this also depends on your ambient lighting)
Native image resolution (projecting on a large area the image may become blurry with low resolution)
Diagonal image size (make sure the resulting image size fits your intended projection area)

The lumens of the projector is the primary indicator of how bright it is.  Contrast ratio is also significant for determining how dark the dark pixels will be when bright pixels are bright, but a lot of that also depends on the type of screen you are using.
The size a projector can project is determined by the overall amount of light it can throw.  As surface area increases, the amount of light that reaches it goes down according to the inverse square law.
This inherently makes sense when you think about it for a minute since you have a fixed amount of light coming out of the projector, but the larger the area you are trying to cover, the less light you have to cover it with per inch.


text:
FFmpeg clarification "position of frame"
Sample output
[Parsed_showinfo_0 @ 0x7f9a3b600000] n:0 pts:0 pts_time:0 pos:194408 fmt:yuvj420p sar:0/1 s:1920x1080 i:P iskey:1 type:I checksum:072007CF plane_checksum:[AAFB805D 153EE2B8 65C9A49C]
[Parsed_showinfo_0 @ 0x7f9a3b600000] n:1 pts:1001 pts_time:0.0417083 pos:366248 fmt:yuvj420p sar:0/1 s:1920x1080 i:P iskey:0 type:P checksum:C9D358B5 plane_checksum:[54D0A047 7C40CC7B 60D3EBD5]
[Parsed_showinfo_0 @ 0x7f9a3b600000] n:2 pts:2002 pts_time:0.0834167 pos:594116 fmt:yuvj420p sar:0/1 s:1920x1080 i:P iskey:0 type:P checksum:A05675B2 plane_checksum:[556FF30D 8CD9462B 0F3E3C6B]
[Parsed_showinfo_0 @ 0x7f9a3b600000] n:3 pts:3003 pts_time:0.125125 pos:779876 fmt:yuvj420p sar:0/1 s:1920x1080 i:P iskey:0 type:P checksum:B17CC362 plane_checksum:[AE090A39 337190E2 B6E52847]
[Parsed_showinfo_0 @ 0x7f9a3b600000] n:4 pts:4004 pts_time:0.166833 pos:952520 fmt:yuvj420p sar:0/1 s:1920x1080 i:P iskey:0 type:P checksum:F7C5D531 plane_checksum:[EA3F8FAF E109630D A582E266]
[Parsed_showinfo_0 @ 0x7f9a3b600000] n:5 pts:5005 pts_time:0.208542 pos:1107392 fmt:yuvj420p sar:0/1 s:1920x1080 i:P iskey:0 type:P checksum:CF48BDB1 plane_checksum:[C87B1176 03581F2B 70EC8D10]

The documents for the showinfo filter define position as

‘pos’ The position of the frame in the input stream, or -1 if this
  information is unavailable and/or meaningless (for example in case of
  synthetic video).

Why does position not start at 0 ?
Why are the positions not sequential 1,2,3,4 etc
When I decompile videos into frames I am trying to label the resulting frames in an order that represents their position in the video to allow me to do things like take different sections of the video at different times but maintain their natural ordering .

The first field (n) is the frame number counter.

I can't say with authority, but it's likely that 'pos' is the byte offset into the file where the frame begins. IOW these aren't frame numbers. In the listing you show the sequence is monotonic, it just doesn't increase by single units. If it is byte offset, it wouldn't start at 0 because there are headers in the file before actual frame data.

that does seem to make sense . I was looking at the problem with my art hat and not my programmer hat .

https://ffmpeg.org/doxygen/3.2/ffplay_8c_source.html#l00160 supports this guess.


text:
Software to allow video presenter to draw directly on the screen
I'm currently enrolled in a coursera.org course which has the presenter standing in front of the camera with a completely black background behind them. While presenting, he would drop directly on the screen as if there's a transparent piece of glass in front of him as shown in the screenshot. I'm wondering how is this possible and what kind of software/hardware could allow this as I'm sure he is not typing backwards. Is the picture inverted and he's really drawing in a glass in front of him or there's another trick?


text:
Little skip in webm videos joined with mkvmerge
I've donwloaded some youtube videos that I want to join. I joined them with mkvmerge, but in the joined video, there are ~5 seconds skips (in VLC the second counter stops and then jumps 5 seconds) at the start of each video I joined (even at the start). Is there another way to join them so I won't have this problem?

Do other players have this problem as well or only VLC?

Try a video editor like Lightworks to join them into one video, there you can cut any black frames and won't have to deal with possible glitches introduced by muxing different videos into one stream.
If your videos are indeed webm and not h264 you might need transcode them into another codec (f.e. with ffmpeg), a production codec like MJPEG or any lossless codec might be suitable as an intermediate codec so you don't loose much visual quality after exporting your finished video.

I've tried using video editors to join videos in the past, but these programs allways try to reencode the videos. Also I was told to use mkvmerge precisely to avoid recoding them to anything (even MJPEG) so they didn't lose quality.

Sure muxing is always the lossless method.
You can also use ffmpeg to cut the file without re-encoding. Might be a bette solution than mkvmerge.

Maybe try a different tool for muxing your files all into one?  Like ffmpeg's concat meta-demuxer.  (the concat filter (-vf concat) doesn't work with -codec copy, but -f concat for the input does.)
https://trac.ffmpeg.org/wiki/Concatenate
Probably your pauses in the concatenated video are from a timestamp glitch in the merged file.  The mkvmerge manual sheds some light on how it does timestamps for the resulting file.
You could check the frame pts values in your merged file with ffplay -vf showinfo (from ffmpeg).  (or ffmpeg -i merged.mkv -vf showinfo -f null - to not show the video.)  If there are big gaps in the pts (presentation timestamp) of frames on the merge boundaries, then that's why the player is pausing.
Using a different tool to concat (like ffmpeg) might solve it.  Or you can do what Prof. Sparkles suggested, but without actually encoding to lossy mjpeg, and then back to lossy h.264.  Tell ffmpeg that the input frames should be considered 24000/1001 fps CFR, and that it should generate new PTS values, ignoring the input timestamps.  (old question, so not digging up the details on how to do it.  check the ffmpeg manual.)


text:
Why is rendered playback slower than my project?
I have a project that's 1280X720 @25
I do have clips in the project that are various resolutions, but this hasnt seem to be a problem.
I render as the "Match the Project Settings" and everytime the video plays back much slower.
How to fix?!
Also sometimes my project becomes off time. But if I restart Vegas it fixes itself.

How much slower is much slower?  What do you mean by your project becoming off time?

Do you mean the video renders slower than the preview in the editor or do you mean the final rendered video plays back more slowly than the preview in the editor?

What and how did you set the "project properties" ?

This was resolved due to incorrect audio sample rate with my DAW. In Vegas I was editing in 24 bit 48,000Hz. After render, my systems was attempting to playback the video file at 16bit 41,000Hz which will cause this effect.


text:
QuickTime File Format (Atoms & Flags)
What is the purpose of Media Atom 'flags' within the QuickTime videos, I see for the most part they are set to zero but what does this achieve?
Documentation I am reading is the following: https://developer.apple.com/library/mac/documentation/QuickTime/qtff/QTFFChap2/qtff2.html

The Media Atom object does not have a Flags field, but the Media Header Atoms does:

Flags - Three bytes of space for future movie header flags.

In which case it's basically say, these values are reserved for future use, and presently are just byte alignment packing.
In most RFC's these area's are called Reserved as compared to flags.
This would explain why they are zero, as by the spec, they should be set zero, so in the future none zero value can be interpreted to mean "something".
If I'm mistaken the section you refering let me know.

They are a type of metadata specific to the QuickTime container.
They can contain all kinds of extra information for the video player to read out and use.

QuickTime movie atoms have an atom type of 'moov'. These atoms act as
  a container for the information that describes a movie’s data. This
  information, or metadata, is stored in a number of different types of
  atoms. Generally speaking, only metadata is stored in a movie atom.
  Sample data for the movie, such as audio or video samples, are
  referenced in the movie atom, but are not contained in it.


text:
Audio monitoring w/ headphones through HDMI port
I'm looking at a new camera that has a mic in and audio control, but no headphones out. Is there a way to get live audio out of a camera using the HDMI port and plugging into headphones? I want to be portable, so plugging into a monitor and then from the monitor to the headphones is not practical.

What you want is generally called an "HDMI audio extractor". There are several hardware products on the market that will extract the audio in the HDMI stream to an audio out connection and pass-through the video part.
A search on ebay gives you several results: http://www.ebay.com/sch/i.html?_nkw=HDMI+audio+extractor
Though if you need very high quality audio you probably need a more professional product with a good built-in DAC (digital to analog converter). HDMI audio is digital so it needs to be converted to an analog signal and the hardware used in these products isn't meant for high fidelity audio production. Or buy a cheap one with an digital output and use an external DAC.

What you can always do is intercept the signal before it goes into the camera. Buy a small mixer, plug the mic into it and use the headphone out of the mixer to monitor the mic. Then take the master stereo out of the mixer and run it into your camera. You should get on the camera what you hear on the phones. You may want one of the HDMI audio extractors to confirm it but once its been confirmed you can use the mixer as you wish.

This would work, though it has the minor issue that if something happened to the audio path between the mixer and the camera, you wouldn't know about it until it was too late, after shooting is done.  You could work around that by using a VU meter in camera (using ML if necessary to get one) in order to make sure there is an appropriate looking signal.


text:
What is the best tool to increase sound of MTS video without need to re-encoding this video?
I need just increase sound of my MTS video. But I'm very afraid to lose the quality of video because it is classical music and intonation is very important.

Is it sound that you can pull from another source, simply gaining up the sound will likely have noise floor problems if it is too low.  You can demux the audio from the video and then boost and re-encode only the audio.

The setup that i use for something similar is:
Step 1 - demux
avconv -i in.mts -an -c:a copy video.mkv -c:a copy audio.ac3

Step 2 - audio editing
For this i just open my audio.ac3 in Audacity and normalise the sound. At this time it may be a good idea to try to remove the noise. I reencode into Vorbis, but it is up to you what you wish to do. Let's say you save into audio.oga
Step 3 - mux
avconv -i video.mkv -i audio.oga -c:v copy -c:a copy out.mkv

Notes

Video was getting copied all the time. So no quality loss is possible from that.
You can drop the video demuxing, and just grab it directly from the original in the third step. But i find it just makes the process much cleaner when you know where everything is.


text:
How to convert a .m4v video/audio file to .mp4 on Windows-7, for free
Does Windows-7 already have something that does this?
Or is there a free download that does it?

Somewhat of an duplicate of: Can I manually change an .mp4 to .m4v by changing the extension in the Finder (mac) or explorer (win)?
MP4 and M4V are essentially the exact same thing, M4V is usually used to indicate video only files but some sofware/companies are using it for standard MP4 files with video AND audio (lots of Apple software f.e.).
It's just a convention to indicate the type of content. An audio only MP4 f.e. would have the extension .m4a.
You can just rename the extension from .m4v to .mp4.


text:
Advice on how to determine right camera equipment and set up for multi-sport court?
We are building a 65ft x 30ft multi-sport court with 13ft walls all around (similar to the one pictured) and we would like to know what video camera equipment would be the most appropriate in order to get a live feed of the action 24/7.
We would like the cameras to be up high, anywhere around or on top as needed. Fixed, unmanned. They also need to be able to withstand being hit by (tennis, basketballs, soccer balls, etc) and have HD quality of at least 720p. No need to be able to move it or zoom with it remotely.
According to my research, there are security cameras that could possible do the work, considering they can shoot HD, but would the video look smooth? Would fps be a limiting factor?
Some other questions:

What are some of the minimum specs I should be looking for in order to shoot live sports?
Would 2 cameras be enough? Or 4 be needed? Could a wider-angle camera replace the need for more than two cameras? We're aiming for <400$, per piece, is that realistic?
Would it be better to place them on (top of) two opposite corners or right on the middle at either end? Or maybe in the middle of the court facing opposite ends?
We want to have every inch of the court covered. And most be able to see up high for basketball goals and down low for small soccer goals.

I understand we should be looking for HD-SDI (over HDMI) able equipment as it would allow us to run longer cables as needed, correct?
With all cameras in place, where would all feeds converge? Would it require a tricaster/studio board or could it go directly into a video card/laptop? Trying to keep it as simple and cost effective as possible.
The main purpose of the live feed is to show it in screens for spectators outside, with streaming as a second priority.
Lastly, is there any software that would allow me to plot or draw the vision field of a camera? Or anything remotely similar using geometric and physical data? Not even sure if those are the proper technical terms but hopefully you get what I mean.
Thank you very much.

Instead of the Teradek unit, I would try the new Epiphan Pearl, which can stream and record to/from multiple sources.

The GoPro would be a perfect candidate for what you want.
It's a so called "action camera" and is a very robust (water tight with case) wide-angle camera that can shoot in very high frame rates with HD resolution (even more at lower frame rates).
Suitable recording options for high speed sport events would 1080p @ 60FPS or 720p @ 120FPS.
The camera also has a live raw HDMI output, its very suitable for live monitoring and recording.
Also the camera has in-offical scripting capabilities which makes it very easy to set the camera up for un-manned opertation.
You will only need to get a DC battery pack adaptor because the GoPro cannot be used without a battery inserted. It's a dummy battery that connects the camera to a DC power supply.
The GoPro Hero3+ Black, their best model, is available for 400$ or a bit less depending on the shop. There is also the Silver Edition for 300$ which should be enough for what you need, it also has HDMI out and 1080p @ 60fps.
Regarding your question about Security Camera, most of them have a rather bad video quality (in comparison to film cameras) and usually low frame rates that aren't suitable for sport events. They are very specialized cameras that often directly record to files instead of giving you a live stream (atleast the cheaper ones).
The capturing on the other hand can get quite expensive, you can of course use a standard PC to capture a camera but you would one capture card per camera and capture cards that support 1080p @ 60 FPS are rather expensive in the 700-1500$ range.
There is also specialized studio equipment for these kind of things that handle multiple inputs but that again is also very expensive and will cost your around 10.000-15.000$
I'd say with a GoPro in wide-angle mode about 2 cameras are enough to cover the whole court when you put them in opposite corners. 4 would probably offer nicer perspectives but that depends on your budget.
If you are on a really tight budget I recommend you opt for 30FPS, not as cool for sports but then again most users don't even have the bandwidth for 1080p@30FPS.
Then you can opt for the even cheaper GoPro White Edition and use a lot cheaper capture card like a BlackMagic DeckLink for 145$ in combination with a standard PC.
When it comes to setting up streaming servers that handle the capture from the PCs and stream it to the web I recommend you hire a professional developer, this is not an easy task at all and can give you a lot of headaches if you have no experience with that matter.
Alternatively you can opt for one these things, they are rather in-expensive and are more compact and would spare you the hassle of a complicated server setup. It automatically streams to streaming services like ustream or YouTube, or have your own website integrate the RTMP stream that it produces.
It would definitely be the cheapest solution, though 1080p @ 60FPS is not possible with this solution, when opting for this device I would go with the GoPro White Edition aswell.
Though 720p@60FPS is possible with this solution, so that might be good alternative if resolution isn't as important as frame rate to you. I'd probably recommend the 720p@60FPS option, its the overall cheapest and high frame rates always win over high resolution when it comes to sport (in my opinion).
Hope that helps you.


text:
How to create and film ghost special effects
I need to film a piece that is supernatural in nature and has several characters that are ghosts. I've thought of numerous ways of accomplishing this but would like some suggestions on which would be the easiest and produce the best results.
Fortunately I am going to be shooting at a location and I would like to have several camera angles as well as a moving camera for some scenes. The problem is I have several characters that are ghosts. I've thought about planning every character's position carefully and then doing a lot of room shots, angles, and movements, and then putting up green screens and filming each character in the same position where they would be in the video so that I may make them transparent and give them a ghostly effect. That seems like it's very complicated though and it also seems like the editing will be a pain.
Is there any easier or more effective way to give several characters a ghost effect without having to resort to green screening them? I have thought about make-up. Also, if green screening is the way to go, would it be wisest to take the green screen on location and put it over the backgrounds and run the camera through the same courses as I did when shooting the background?

There are so many interesting ways to do this.
One of the easiest ways (in-camera, no post production work) is to use a piece of glass. Film Riot did a tutorial on it, they explain it best, see below:

Or you could go with a bit of post production work, after effects being my go to tool that I use. Add a background video layer (without ghost), then add your ghostly image, same shot, but this time your ghostly image is brightly lit and everything else is dark. Then change the mode of the ghostly layer to 'add' (or other to create different effects) to create the ghostly effect. See tutorial below:

Hope that helps your ghostly scenes.

If you ditch your plan to use moving shots you can do a simple background subtraction which will look a lot cleaner than greenscreen given this is a low cost production.
This works by having a shot of your scene without any actor in it e.g. only the background and then film your scene with the actors without moving the camera, afterwards you can use a program like After Effects to do a background subtraction, so everything that is different to your previous background only shot will be usable as a mask or the inverse.
That is pretty much the easiest way to achieve such an effect.
Though it is limited and you have to be very careful about what and how you shoot your scenes.

Do not move the camera in the slightest way during every scene, the background needs to as pixel exact as possible in both shots.
Do not have a moving background behind any of the actors, you can have moving objects in the background but they can not intersect with the actor. You can later rough masks to remove moving parts in the background that don't intersect with the actor. It's still possible to have intersecting objects but you will have to reside to rotoscoping which can be a pain in the ass.
If the "ghost effect" you want to give your characters are meant to be visually different for every character you also do not want actors to touch each other or you have to reside to rotoscoping again which in that case can be even more difficult if you have to mask things like fingers for every frame.
Avoid noise in your camera footage and do not change any setting in the cameras between the plane shot and the actual scene shot

Greenscreen is not that hard to use but diffrences in camera angle, camera movement and focal length can make you characters look a bit funny and it will be very obvious that they were shot infront of a greenscreen.
If you decide to use greenscreen I suggest you use a motorized dolly for moving shots that can be programmed for specific movements. You can also mix both techniques and use greenscreen only for moving shots but if you want to do this with the least work possible I would not use moving shots and greenscreen at all.

Ooh, +1 for the background subtraction idea. I did not think of that!

+1 Better description of what I was trying to describe in my answer.

A few good options to consider:

If you disobey the 180 degree shutter rule, and shoot at a lower shutter speed, you'll get more motion blur in your shot. Whether or not this is what you're going for is up for debate (it'll produce a dream sequence - ghostly like effect), but it's worth trying out. Note that EVERYTHING in your shot with have increased motion blur, not just your actors. So, maybe make sure you plan out your shots to have a still background + just ghost characters.
As opposed to green screening your subjects into your background (often looks superficial unless your super good at matching the RGB channel values for the foreground and background), you might consider rotoscoping the actors w/effects such as a slight glow, maybe a tint to make them less saturated, maybe track their movements and add some smoke particle effects, etc. While this is a pain in the butt, I think it'll look more realistic than the green screen route.

If you don't mind using a computer. There is a great solution (for me at least) which is called Blender, if you don't know about it, it is a free sortware that lets you do 3D and mix 3D with video, but it also lets you do video editing and a lot more staff. Google for Blender.
With that you don't need to be very precise to record your ghosts, just record the people separately and in Blender create a plane with each of the ghosts in 3D, assign them the transparency factor you wish, do whatever special effects you might like to do in 3D or just visual, like halos around ghosts and that stuff, place those planes and ghost as you see fit your needs in the scene and render your video.
This way, ghosts can walk in front of AND behind people on set (but for this you will need everybody, ghosts and not ghosts to be recorded using chroma).
Here are two images one from Blender's 3D view port and another one with the final result.
I have done a simple (without big halos and staff) example in Blender's compositor, you can see the nodes and the final result in the background. You can adjust transparency and apply more filters and effects.

Welcome to Video Production.SE.  Could you include some more detail about how you would actually get them as layers in Blender.  While this does provide a way that can use free tools, it is a rather complex process compared to most of the others and some further explanation of how to create video such that it can be layered and how the layering works in Blender would make it far more usable to someone who hasn't used Blender or 3d animation software before.

Actually I'm working on a scene with planes, I will add an image and the resulting. I'm not working with ghosts, but a fairy appearing and disappearing is more or less like a ghost.

It sure does, as you can see in the image I posted, the background is a video with a green screen and and the puppet, you can also see the puppeteer, but with blender it could be easily masked out. Check how chroma and masking is done in these video: https://www.youtube.com/watch?v=hgqTrjPJdLY There are plenty of videos explaining the technique, this video only shows the process...

Wow, you are right, I'm a little slow today.

For fixed camera shots, if you plan the shot so that they don't pass over any other actors, you can simply shoot them on one plate and shoot the rest of the actors on another plate.  You then mask the one plate over the other so that they appear semi-transparent and possibly use a blurred difference mask for adding an edge glow.
Greenscreening overall is probably the easiest, though it probably won't produce the best quality result possible.  As long as you plan your shots well (try to avoid wide shots where the movement around the scene may be awkward to match), then it shouldn't be too hard to put together.  Even lighting shouldn't particularly matter since ghosts are often depicted as self lighting and so the glow will remove any inconsistency the eye might see in how the subject is lit.  Note that the big caveat for this to work is you need to be applying color and lighting effects to the ghost that make it so that it shouldn't match the lighting of the scene it is shot in.


text:
WAX - How do I make it so the PiP can go anywhere?
So, I make videos, and I needed to make a PiP of a comment in the video. I made the PiP, but whenever I move it upwards far enough, it gets hidden, as if there was an invisible video wall. To help you guys better understand it, I took a picture of my wax setup: https://i.sstatic.net/XEUve.jpg
It's a bit hard to see, but you can see the top part hidden and such.
Thanks for reading, and thanks for trying to help :)

not really an answer to your question but may I suggest using Lightworks. It's a free modern NLE with support of many formats and modern user interface. You will get a lot more support and tutorials for this tool aswell.
http://www.lwks.com/

I don't really feel like making an account just to use it. :/


text:
Stock footage search service
Is there any service where I can describe stock footage that I need using human readable search terms and sentences and send out a search request to multiple footage archives at once, so I will not have to contact each one individually, that will then use real humans or otherwise search intelligently and send me a list of suggested and relevant footage clips?

I don't know, but if there isn't you might consider Amazon http://en.wikipedia.org/wiki/Amazon_Mechanical_Turk which is designed for this sort of work. It's not free.

yeah.  I was going to say mechanical turk.

I don't know what you mean by human readable search terms, as opposed to keywords or tags?
But for a meta search directory service I would recommend (know of)
http://www.footage.net/
(If anyone knows of any additional search engine stock video directories, I would love to know about it as well)
Otherwise, ya, you would be going through each service looking for footage.
These are the stock services that I am aware of:
http://www.shutterstock.com/video/
http://www.gettyimages.ca/footage/ <- used by major media outlets
http://www.pond5.com/
http://www.alwayshd.com/
https://www.videocopilot.net/products/ <- geared more to adding effects to clips
http://www.footagesearch.com/
And many more... I am sure others can chime in with their favorite sites.

I use VideoHive - large collection of clips and affordable prices.


text:
I only have the .mp4 files from a Sony XDCAM EX shoot, is there a way I can still convert them for use in AfterEffects on Windows?
I no longer have access to the original recordings and the weird excess of files that Sony likes to bundle with the video you actually need.

I'm running Windows 8.1 and Adobe After Effects CS6, and I've now got Sony's "XDCAM EX ClipBrowser V2.6".
Is there a way around Sony's encryption or are my options limited to reshooting the whole project?
Thanks in advance!

MP4 files should be all you need.  There shouldn't be any encryption on the files.  It is possible you may need to download a codec.  MP4 files are just a container format, so different codecs could be used within it.  It is possible that you don't have the needed codec installed, but if you do, the files should just open in After Effects without issue.

Though unlikely, the camera would shoot not in spec with the MP4 format if thats the case. Every codec supported by MP4 is supported by After Effects natively.

@ProfessorSparkles - yeah, can't think of any other reason it wouldn't work though, unless it has perhaps been otherwise misshapen by some other process.  I would fully expect it should just work, but I'd assume the OP already tried that and it didn't.


text:
drop similar frames
I'd like to record a very long video from webcam which will be mostly the same.
I'd like to drop intermediate frames that are very similar to each other to save on filesize and also make it easier to find "interesting" parts of the video later.
The frames will likely not be identical but should be similar (I imagine I'll have to experiment with thresholds)
I am familiar with both mencoder and ffmpeg but have been unable to find any options to do what I need.
I'd prefer to drop the unwanted frames at time of recording but if it must be done as a post-process that is ok however - the video needs to have a timestamp on it, obviously this will interfere with any similarity test so it either needs to be done at time of recording or the similarity test needs to ignore a predefined section of the video without dropping it.
FYI this is the command I am using currently but without the desired framedropping.
ffmpeg -f video4linux2 -s 800x600 -r 15 -i /dev/video1 -maxrate 800k -minrate 1k -bt 800k -bufsize 2M -filter drawtext='text=%{localtime }:fontfile=/usr/share/fonts/truetype/DejaVuSans-Bold.ttf'  -f h264  out.avi -y

What are my options?

Incidentally the video will not be streamed live so there is no minimum bandwidth concren

Keep an eye on this software, developed at CMU. It removes uneventful pieces of video.  There's a link to the paper in the press release.  http://www.cmu.edu/news/stories/archives/2014/june/june25_livelightvideotrailers.html

Does this actually have a Video Production related use case?  I'm having trouble seeing how this really relates to Video Production.  It seems to be more specifically a security system kind of requirement that doesn't really apply to any video production situation I can think of.

It is actually quite easy using a videofilter with select.
This is quite sensitive to video changes:
-vf "select=gt(scene\,0.0098)"

whereas this is not so sensitive:
-vf "select=gt(scene\,0.3)"

EDIT (added your command)
so your command would look like:
ffmpeg -f video4linux2 -s 800x600 -r 15 -i /dev/video1 -maxrate 800k \
-minrate 1k -bt 800k -bufsize 2M -filter \
drawtext='text=%{localtime }:fontfile=/usr/share/fonts/truetype/DejaVuSans-Bold.ttf'  \
-vf "select=gt(scene\,0.3)" -shortest -c:v libx264 out.mp4 -y

P.S. You need to explicitly state the codec libx264 and not just tell it -f h264 and why on earth would you be using avi???

This seems to work except the output duration is the same as the input. I expected the new frames to all be the same duration (e.g. 1/15th of a second) resulting in a quick jump past the boring bits.
I tired adding -r 15 as the last argument before the output filename but it had no effect.

It seems you will probably want to use the -shortest command, which I forgot to put in.

I found this thread. There you can see that Avisynth has a plugin (GetDups) which will allow you to do exactly what you want.

You may reach it by mpdecimate video filter (followed by setpts filter for the correct timing).
Add these filters to your filter chain:
mpdecimate,setpts=N/FRAME_RATE/TB

so your command will be
ffmpeg -f video4linux2 -s 800x600 -r 15 -i /dev/video1 -maxrate 800k -minrate 1k \
   -bt 800k -bufsize 2M -filter:v \
    drawtext='text=%{localtime }:fontfile=/usr/share/fonts/truetype/DejaVuSans-Bold.ttf', \
    mpdecimate,setpts=N/FRAME_RATE/TB out.avi -f h264 -y

(In the case of need the filter mpdecimate may be adjusted by its options hi, lo and frac but the default values work fine.)


text:
After Effects - Recreate a "distortion" or a special Radial Blur effect / Slowly pitch sound down
I would like to re-create an effect from the game Dishonored.
The FX happens when I teleport or when I slow down time, the screen gets some radial blur and a strange kind of distortion at the edges. While that happens, the game sounds also get pitched down slowly, depending on how much radial blur is on the screen. Here's a video showing the effect:
Click me...
Here's an another video, showing the game slowly slowing down, and the radialblur&distortion increases, sound slowly pitches down.
Click me...

You can recreate this effect with the CC Radial Blur effect set to "Fading Zoom" together with the Ripple effect or the Turbulent Displacement effect.
Apply these effects to an Adjustment layer above your video layer and add a round mask in the middle with some feather to have the blur and distortion only on the sides of the screen. Use separate Adjustment Layers for each effect to fine tune the strength of both effects with separate masks.
You also want to set the size wave size of the ripple effect to something like 60/30 to have it closer to the look in Dishonored and to not have it so uniform. Setting it to asymmetric might be a good ideas as well
To get even closer you can apply some other distortion effects available in After Effects, just play around a bit. The Turbulent Displacement effect is also a great alternative to the Ripple effect, might even be closer to the look in the game. It has a far less uniform displacement.

And what about the sound pitching down slowly and then back up?

I just tested it now, and the CC Radial Blur is the only thing that looks like Dishonored's Radial Blur effect. The ripple effect or the Turbulent Displace effect didn't do the same thing.

Well you should use them in conjunction not either the blur or the ripple/displace, the blur in Dishonered isn't just a static blur, it floating and distorting the picture, for that you need something to displace the picture.
To "slow down" sound you can't user After Effects, thats a whole other question for http://sound.stackexchange.com/.


text:
How to achieve "Acid Burn" saturation?
The TV show 'Utopia' has become renowned for its stylized visuals, including a type of saturation that is frequently described by reviews as "Acid Burned"...

Director Marc Munden, who shot the first three episodes, set an incredible visual tone from the start with his use of acid colours and startling symmetry.

From the Guardian.

Channel 4's acid-toned paranoid thriller got off to a disappointing start ratings-wise, but soon built a detail-orientated fanbase whose obsessiveness was almost a match for the show's own graphic-novel nerds.

From the Independent.

What this seems to translate to is incredibly rich and vibrant yellows and greens, with de-saturated blues and washed out darker shades.
How is this achieved, and how could it be reproduced?
Is it entirely modified digitally in post production, or is a mixture of filmic techniques, lenses and post?

The British adaptation of Wallander also prominently used this technique:

As Professor Sparkles said. The entire comment chain was unnecessary. Being insulting, or name calling is not appropriate here.

Wallander (at least the screen shots) dont look similar to Utopia. In Utopia you can see he did a vignette, a darker circle around the movie, like a halo, also the colors are much 'richer'. In Wallander the colors are slightly bleached (destatuated), no vignette, and the yellows again, not a rich yellow but a over bright yellow. Wallander just does not look as rich and vibrant.

I have not seen any movie that used any onset technqiuqes for this look. Of course you want the lighting to give away a certain mood to begin with but there are no special filters needed.
For the post production workflow, there is a great plugin for several video tools like After Effects, Premiere and Final Cut from Red Giant called Mojo that makes it extremely easy to achieve and fine tune such an effect. They also offer other tools to achieve specific filmic looks.
If you don't want to use a plugin or simply want to achieve a more "unique look", you can play with contrast and the individual color channels. I recommend using a "Levels" effect not a "contrast" effect, you usually have greater control with that. Then punch the blue channel up a bit and the green channel aswell but not as much. For some scene you may want to work with masks to strengthen the effect in some areas without overdoing it in others.
What can also help even more to achieve the color distortion but is not available in every video editor is to apply a blue (or other color depending on your desired look) layer over your footage with a blend mode like "Overlay" or "Vivid Light" (that's how they are called in Adobe programs) and adjusting the transparency of the color layer. This tints the image nicely in a blueish dark look.
Play around with different blend modes, you can achieve very interesting effects with that technique. Your video software just needs to support blend modes for that.
You also want a very sharp image, thats important for the effect to really shine and have this "harsh" feeling. Applying a very subtle sharpening effect could be benefical.
You can also add a vignette as used in your first set of screenshots.

Just to add more options, you can also use Blender (http://www.blender.org) which is free software to do what Professor Sparkles describes here.

@YoMismo You will have a much much harder time doing it though.

Really? Have you tried the compositor? I haven't tried After Effects since it is not free, but after trying Blender's compositor I don't think it is that hard.

To add onto what Professor Sparkles said and to give more of a specific answer to your question, I believe this is done entirely in post (but I could be wrong because I have no experience on set). If anything, one could definitely reproduce this (or very close to it) in post by performing a few things:

Remove Noise
Balance your R,B,G channels
Juice the saturation, increase contrast, darken image(changing contrast and saturation can tend to have the same effect, so balance them appropriately favoring a higher saturation)
Push your shadows to cooler temperatures, blues and teals
Apply a vignette
Apply slight sharpening

+1 for reducing noise and specifically mentioning shadows.


text:
Lossy output with FFMPEG JPEG 2000
I'm trying to achieve a lossy JPEG 2000 output with FFMPEG, but no success so far.
Using this command line:
ffmpeg -i input.dpx -pix_fmt yuv420p -vcodec libopenjpeg output.jp2

As a result I get lossless output, which is a default setting for JPEG 2000. I tried -b:v and -q:v, but they both have no impact to the output.
Does anyone know a command that changes the quality/compress the output?
Any kind of help is really appreciated. Thank you!

Did you try using the -compression_level flag? It takes an int from 0-100 afaik (maybe the range is even higher, the docs just say "int").
That should set a lossy compression strength.
There is also an interesting blog post about creating DCI compilant JPEG2000 encodes with FFMPEG for DCP's. Which require lossy encoded JPEG2000.

Thank you for your answer! The -compression_level flag does indeed reduce picture quality/file size. The range is 0-9999999999999. The only problem with this method is that -compression_level flag is not a defined scale. I'd like to compare the coding efficiency of different encoders. By using -compression_level flag I have no common value, which would allow me to compare different encoders.

The -profile:v flag mentioned in the blog post might help you. It applys specific encoding profiles that are also found in other encoders.
I cant find it in the documentation specific to JPEG2000, to know which profile is which you may have to look into the source.

Btw. if you just want to compare JPEG2000 implementations I recommend to just download the OpenJPEG binary directly and work with that, afaik FFmpeg only partially implents it. You will have far more options and better documentation: https://code.google.com/p/openjpeg/wiki/Downloads?tm=2

The -profile:v flag defines AFAIK such things as image size, wavelet levels etc, but not the compression ration. Well, I'll look into this anyway. I want to compare HEVC against JPEG 2000, especially benefits of higher bit depth in combination with chroma subsampling. I tried OpenJPEG, it kinda does the job. But the input formats are pretty sparse. They either don't support higher bit depth or are all RGB.

What is the issue with them being RGB? That doesn't affect the compression in any way, doesn't matter what color space your source has, OpenJPEG will decode them and use the color space provided by you for encoding.
Almost all of the listed formats support 16bit color, much more than HEVC even supports.

Also if you really just want to compress a few images and videos with jpeg2000 and don't need a command line you can use j2k from fnord. Its free and integrates into Photoshop, After Effects and Premiere (if you happen to own any of these, you can also use a free trial).
http://www.fnordware.com/j2k/

I have few thousands images with different parameters, therefore a command line or a batch file would come in very handy. Yeah, I've read about J2K Fnord plugin, but didn't try it yet. OpenJPEG does RGB->YCC conversion by default, I'm fine with it. But if I use a subsampling factor it stretches the image size... Also it applies the same subsampling factor to each component. Maybe I use a wrong command line, but I couldn't find an option to use a different subsampling factor for each component.

Well with photoshop you can do a batch processing aswell. So that wouldn't be an issue.
Fnords JPEG2000 plugin is very feature complete and implents almost all aspects of JPEG2000 there are.

I tried Fnord's JPEG 2000 plugin, as good as it is, there is no subsampling function implemented. And this is something I definitely need.

Ancient thread now, but one of the two encoders you want to compare can hit a bitrate target fairly accurately.  Encode with some setting with libopenjpeg, then make a HEVC encode with 2-pass at that bitrate.


text:
Repair corrupted video files
After experimental restauration of btrfs sparse file image, a lot of my video files have missing or added bytes, but only some (file sizes are identical to size of original except < 100 bytes). Is there a program which can

recognize the video container and encoding (could may also be done separately with a script)
repair the video file based on eventually existing checksums (I have no idea how popular video formats work)
recognize missing bytes causing the failure of rendering for single images/sequences and replace them with black images

(1. is optional, 2. and 3. alternatives for each other)?

Completely depends on the video codec and container format, there is no general tool to fix corrupted video files.
Regarding avis with missing headers there is a good answer on this question.
The info there also helps with recovering other video formats.
To find more info about a certain file I recommend using MediaInfo in addition to ffprobe. It offers some more info about codecs and container properties than ffprobe and is easier to read.
If chunks in the video stream are corrupt it won't hinder playback of the stream you will just experience artifacts around these chunks.


text:
mistake importing footage
I am kind of new to video (1 year). When I import video footage into Premiere, I sometimes get duplicate clips. Only the long ones. I think I am not importing my footage correctly. Does it have to do with the clip, if it is long, is really spanning 2 clips? The video is HD, mostly those Canon MTS files. What is the correct way to import into Premiere, just started working with CC (2014) version?

It is possible that Premiere is detecting a spanned file and automatically connecting them.  If a file goes beyond 4GB, it may have to be split in to two files due to limitations of the file system used on some memory cards.  It is possible that when you load the file in to Premiere, it recognizes the file was split and puts them back together for both parts that you import.

This would be what it is - if my memory serves me correctly, a .MTS is usually the wrapper codec for an AVCHD file, which is commonly used on Canon's dedicated video cameras (not their DSLRs, though).

To import into Premiere Pro CC 2014 simply click on the Media Browser tab and select (or multi-select) the files you wish to import. Right-click and click import. Note if you double click on a file, default behavior is to open it for preview.
Here's an adobe help on importing as well:
http://helpx.adobe.com/premiere-pro/using/importing-assets-tapeless-formats.html
and a how-to video on importing:
http://tv.adobe.com/watch/learn-premiere-pro-cc/import-video-and-audio/

Not paying attention...I was importing the whole card folder by dragging instead of the actual clip files! Some of the clips were long and must have been too big for the filesystem on the card?  When I import the actual clip files through the media browser - Presto - no duplicates and now I see skips in the numerical sequences of the clips - e.g. MTS0000, MTS0001, MTS0004, MTS0007. And the spanned files were always the longest ones.