title: OpenCV VideoWriter using ffmpeg with "Could not open codec 'libx264'" Error
body: <p>I am new to OpenCV, and I want write Mat images into video using VideoWriter on Ubuntu 12.04. But when constructing VideoWriter, errors came out. </p>
  
  <p>It seems that OpenCV invoke ffmpeg API using default parameters and ffmpeg invoke x264 using its default parameters. Then these setting is broken for libx264. Thus the "Could not open codec 'libx264'" error. </p>
  
  <p>Anyone has ideas to solve this problem?</p>
  
  <p>More specifically:</p>
  
  <ol>
  <li>anyone knows where and how OpenCV invoke ffmpeg API?</li>
  <li>how to change ffmpeg default settings using code, hopefull, can be easily embeded into OpenCV?</li>
  <li>will changes of default in ffmpeg be carried to libx264?</li>
  </ol>
  
  <p><strong>Errors:</strong></p>
  
  <pre><code>1. Uising CV_FOURCC('H', '2', '6', '4')
  [libx264 @ 0x255de40] broken ffmpeg default settings detected
  [libx264 @ 0x255de40] use an encoding preset (e.g. -vpre medium)
  [libx264 @ 0x255de40] preset usage: -vpre &lt;speed&gt; -vpre &lt;profile&gt;
  [libx264 @ 0x255de40] speed presets are listed in x264 --help
  [libx264 @ 0x255de40] profile is optional; x264 defaults to high
  Could not open codec 'libx264': Unspecified error
  
  2. Using FOURCC = -1 to invoke user customized codec
  OpenCV Error: Unsupported format or combination of formats (Gstreamer Opencv 
  backend doesn't support this codec acutally.) in CvVideoWriter_GStreamer::open, 
  file /home/XXX/Downloads/opencv-2.4.8/modules/highgui/src/cap_gstreamer.cpp, 
  line 505 terminate called after throwing an instance of 'cv::Exception'
  what():  /home/XXX/Downloads/opencv-2.4.8/modules/highgui/src/cap_gstreamer.cpp:
  505: error: (-210) Gstreamer Opencv backend doesn't support this codec acutally.
  in function CvVideoWriter_GStreamer::open
  </code></pre>
  
  <p><strong>Codes:</strong> </p>
  
  <pre><code>int main(int argc, char *argv[])
  {
      VideoWriter outputVideo;
      bool fourcc_on = true; //switch on / off different error
      if (fourcc_on)
          outputVideo.open("outVideo.avi", CV_FOURCC('H', '2', '6', '4'), 25, Size(100, 100), true);
      else
          outputVideo.open("outVideo.avi", -1, 25, Size(100, 100), true);
  
      if (!outputVideo.isOpened())
      {
          cout  &lt;&lt; "Could not open the output video for write" &lt;&lt; endl;
          return -1;
      }
      return 0;
  }
  </code></pre>
  
  <p><strong>OpenCV Configuration:</strong></p>
  
  <pre><code>-- Detected version of GNU GCC: 46 (406)
  -- Found OpenEXR: /usr/lib/libIlmImf.so
  -- Looking for linux/videodev.h
  -- Looking for linux/videodev.h - not found
  -- Looking for linux/videodev2.h
  -- Looking for linux/videodev2.h - found
  -- Looking for sys/videoio.h
  -- Looking for sys/videoio.h - not found
  -- Looking for libavformat/avformat.h
  -- Looking for libavformat/avformat.h - found
  -- Looking for ffmpeg/avformat.h
  -- Looking for ffmpeg/avformat.h - not found
  -- Could NOT find JNI (missing:  JAVA_INCLUDE_PATH JAVA_INCLUDE_PATH2 JAVA_AWT_INCLUDE_PATH) 
  -- 
  -- General configuration for OpenCV 2.4.8 =====================================
  --   Version control:               unknown
  -- 
  --   Platform:
  --     Host:                        Linux 3.8.0-38-generic x86_64
  --     CMake:                       2.8.7
  --     CMake generator:             Unix Makefiles
  --     CMake build tool:            /usr/bin/make
  --     Configuration:               RELEASE
  -- 
  --   C/C++:
  --     Built as dynamic libs?:      YES
  --     C++ Compiler:                /usr/bin/c++  (ver 4.6)
  --     C++ flags (Release):         -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -msse3 -ffunction-sections -O3 -DNDEBUG  -DNDEBUG
  --     C++ flags (Debug):           -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -msse3 -ffunction-sections -g  -O0 -DDEBUG -D_DEBUG
  --     C Compiler:                  /usr/bin/gcc
  --     C flags (Release):           -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -msse3 -ffunction-sections -O3 -DNDEBUG  -DNDEBUG
  --     C flags (Debug):             -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -msse3 -ffunction-sections -g  -O0 -DDEBUG -D_DEBUG
  --     Linker flags (Release):      
  --     Linker flags (Debug):        
  --     Precompiled headers:         YES
  -- 
  --   OpenCV modules:
  --     To be built:                 core flann imgproc highgui features2d calib3d ml video legacy objdetect photo gpu ocl nonfree contrib python stitching superres ts videostab
  --     Disabled:                    world
  --     Disabled by dependency:      -
  --     Unavailable:                 androidcamera dynamicuda java
  -- 
  --   GUI: 
  --     QT:                          NO
  --     GTK+ 2.x:                    YES (ver 2.24.10)
  --     GThread :                    YES (ver 2.32.4)
  --     GtkGlExt:                    NO
  --     OpenGL support:              NO
  -- 
  --   Media I/O: 
  --     ZLib:                        /usr/lib/x86_64-linux-gnu/libz.so (ver 1.2.3.4)
  --     JPEG:                        /usr/lib/x86_64-linux-gnu/libjpeg.so (ver )
  --     PNG:                         /usr/lib/x86_64-linux-gnu/libpng.so (ver 1.2.46)
  --     TIFF:                        /usr/lib/x86_64-linux-gnu/libtiff.so (ver 42 - 3.9.5)
  --     JPEG 2000:                   /usr/lib/x86_64-linux-gnu/libjasper.so (ver 1.900.1)
  --     OpenEXR:                     /usr/lib/libImath.so /usr/lib/libIlmImf.so /usr/lib/libIex.so /usr/lib/libHalf.so /usr/lib/libIlmThread.so (ver 1.6.1)
  -- 
  --   Video I/O:
  --     DC1394 1.x:                  NO
  --     DC1394 2.x:                  YES (ver 2.2.0)
  --     FFMPEG:                      YES
  --       codec:                     YES (ver 55.58.105)
  --       format:                    YES (ver 55.37.101)
  --       util:                      YES (ver 52.78.100)
  --       swscale:                   YES (ver 2.6.100)
  --       gentoo-style:              YES
  --     GStreamer:                   
  --       base:                      YES (ver 0.10.36)
  --       app:                       YES (ver 0.10.36)
  --       video:                     YES (ver 0.10.36)
  --     OpenNI:                      NO
  --     OpenNI PrimeSensor Modules:  NO
  --     PvAPI:                       NO
  --     GigEVisionSDK:               NO
  --     UniCap:                      NO
  --     UniCap ucil:                 NO
  --     V4L/V4L2:                    Using libv4l (ver 1.0.1)
  --     XIMEA:                       NO
  --     Xine:                        NO
  -- 
  --   Other third-party libraries:
  --     Use IPP:                     NO
  --     Use Eigen:                   NO
  --     Use TBB:                     NO
  --     Use OpenMP:                  NO
  --     Use GCD                      NO
  --     Use Concurrency              NO
  --     Use C=:                      NO
  --     Use Cuda:                    NO
  --     Use OpenCL:                  YES
  -- 
  --   OpenCL:
  --     Version:                     dynamic
  --     Include path:                /home/shixudongleo/Downloads/opencv-2.4.8/3rdparty/include/opencl/1.2
  --     Use AMD FFT:                 NO
  --     Use AMD BLAS:                NO
  -- 
  --   Python:
  --     Interpreter:                 /usr/bin/python (ver 2.7.3)
  --     Libraries:                   /usr/lib/libpython2.7.so
  --     numpy:                       /usr/lib/python2.7/dist-packages/numpy/core/include (ver 1.6.1)
  --     packages path:               lib/python2.7/dist-packages
  -- 
  --   Java:
  --     ant:                         NO
  --     JNI:                         NO
  --     Java tests:                  NO
  -- 
  --   Documentation:
  --     Build Documentation:         NO
  --     Sphinx:                      NO
  --     PdfLaTeX compiler:           /usr/bin/pdflatex
  -- 
  --   Tests and samples:
  --     Tests:                       YES
  --     Performance tests:           YES
  --     C/C++ Examples:              NO
  -- 
  --   Install path:                  /usr/local
  -- 
  --   cvconfig.h is in:              /home/shixudongleo/Downloads/opencv-2.4.8/build
  -- -----------------------------------------------------------------
  -- 
  -- Configuring done
  -- Generating done
  -- Build files have been written to: /home/XXX/Downloads/opencv-2.4.8/build
  </code></pre>
  
  <p><strong>FFMPEG</strong></p>
  
  <p>ffmpeg is enable to support OpenCV and libx264 is enabled when compiling ffmpeg.
  By using ffmpeg command line, libx264 is running normally. </p>
  
  <pre><code>$ ffmpeg -i test.avi -vcodec libx264 test.mp4
  ffmpeg -i test.avi -vcodec libx264 test.mp4 &gt; ~/Downloads/ffmpeg_log.txt
  ffmpeg version 2.2.git Copyright (c) 2000-2014 the FFmpeg developers
    built on Apr 24 2014 16:39:51 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
    configuration: --enable-gpl --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-nonfree --enable-postproc --enable-version3 --enable-x11grab --enable-shared --enable-pic
    libavutil      52. 78.100 / 52. 78.100
    libavcodec     55. 58.105 / 55. 58.105
    libavformat    55. 37.101 / 55. 37.101
    libavdevice    55. 13.100 / 55. 13.100
    libavfilter     4.  4.100 /  4.  4.100
    libswscale      2.  6.100 /  2.  6.100
    libswresample   0. 18.100 /  0. 18.100
    libpostproc    52.  3.100 / 52.  3.100
  Input #0, avi, from 'test.avi':
    Duration: 00:00:03.73, start: 0.000000, bitrate: 1757 kb/s
      Stream #0:0: Video: msvideo1 (CRAM / 0x4D415243), rgb555le, 320x240, 1781 kb/s, 15 tbr, 15 tbn, 15 tbc
      Metadata:
        title           : julius.avi Video #1
  File 'test.mp4' already exists. Overwrite ? [y/N] y
  No pixel format specified, yuv444p for H.264 encoding chosen.
  Use -pix_fmt yuv420p for compatibility with outdated media players.
  [libx264 @ 0x25d08e0] using cpu capabilities: none!
  [libx264 @ 0x25d08e0] profile High 4:4:4 Predictive, level 1.2, 4:4:4 8-bit
  [libx264 @ 0x25d08e0] 264 - core 142 - H.264/MPEG-4 AVC codec - Copyleft 2003-2014 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=4 threads=12 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=15 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
  Output #0, mp4, to 'test.mp4':
    Metadata:
      encoder         : Lavf55.37.101
      Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv444p, 320x240, q=-1--1, 15360 tbn, 15 tbc
      Metadata:
        title           : julius.avi Video #1
  Stream mapping:
    Stream #0:0 -&gt; #0:0 (msvideo1 -&gt; libx264)
  Press [q] to stop, [?] for help
  frame=   56 fps=0.0 q=-1.0 Lsize=     321kB time=00:00:03.60 bitrate= 731.0kbits/s    
  video:320kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.409949%
  [libx264 @ 0x25d08e0] frame I:3     Avg QP:15.36  size:  7975
  [libx264 @ 0x25d08e0] frame P:38    Avg QP:26.05  size:  6230
  [libx264 @ 0x25d08e0] frame B:15    Avg QP:28.25  size:  4418
  [libx264 @ 0x25d08e0] consecutive B-frames: 46.4% 53.6%  0.0%  0.0%
  [libx264 @ 0x25d08e0] mb I  I16..4:  1.4% 72.8% 25.8%
  [libx264 @ 0x25d08e0] mb P  I16..4:  1.6%  5.7% 15.1%  P16..4:  7.6%  6.3%  7.4%  0.0%  0.0%    skip:56.3%
  [libx264 @ 0x25d08e0] mb B  I16..4:  0.2%  1.0%  2.0%  B16..8: 13.3%  7.8%  8.7%  direct: 8.3%  skip:58.8%  L0:34.9% L1:36.6% BI:28.5%
  [libx264 @ 0x25d08e0] 8x8 transform intra:37.7% inter:2.3%
  [libx264 @ 0x25d08e0] coded y,u,v intra: 52.1% 42.1% 30.1% inter: 19.6% 9.2% 5.2%
  [libx264 @ 0x25d08e0] i16 v,h,dc,p: 56% 17% 24%  2%
  [libx264 @ 0x25d08e0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 10% 16% 68%  1%  1%  1%  1%  1%  1%
  [libx264 @ 0x25d08e0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 19% 18% 28%  5%  6%  5%  7%  5%  6%
  [libx264 @ 0x25d08e0] Weighted P-Frames: Y:31.6% UV:21.1%
  [libx264 @ 0x25d08e0] ref P L0: 70.5%  9.0% 12.1%  6.5%  2.0%
  [libx264 @ 0x25d08e0] ref B L0: 91.3%  8.7%
  [libx264 @ 0x25d08e0] kb/s:700.56
  </code></pre>