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• How to Write to AVI with OpenCV Python on Windows 10

  29 juillet 2019, par Novak

  I want to write properly formed frames of video data to an AVI.

  All attempts fail.

  What I end up with, after long efforts of debugging, are *.avi files of non-zero length in the desired directory, which will not play with any of multiple video players already installed on my system.

  Please note : High quality answers will be COMPLETE and DETAIL oriented. In particular, questions about writing video with OpenCV tend to generate drive-by responses including little more than another four-letter code to stick in fourcc. Answers which do so without also telling me at a minimum what file extension to use, what file type it will generate, and why it is expected to work over what I give above are unhelpful.

  Here are the salient details of the system :

  Operating System : Windows 10
  Language : Python 3.7, with Anaconda 3
  OpenCV : 4.1.0

  Here Is What I Have Done/Tried :

  Installed FFMPEG as per this link, restarted Anaconda, and verified ffmpeg (ffmpeg -version) from within Anaconda, with the following result :

  ffmpeg version N-94396-g47b6ca0b02 Copyright (c) 2000-2019 the FFmpeg developers
  
  built with gcc 9.1.1 (GCC) 20190716
  
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt
  
  libavutil      56. 32.100 / 56. 32.100
  
  libavcodec     58. 55.100 / 58. 55.100
  
  libavformat    58. 30.100 / 58. 30.100
  
  libavdevice    58.  9.100 / 58.  9.100
  
  libavfilter     7. 58.100 /  7. 58.100
  
  libswscale      5.  6.100 /  5.  6.100
  
  libswresample   3.  6.100 /  3.  6.100
  
  libpostproc    55.  6.100 / 55.  6.100

  Multiple variations on the theme of :

  import cv2
  
  fourcc = cv2.VideoWriter_fourcc(*"DIVX")
  
  vidout = cv2.VideoWriter(baseDir + "videos\\foo.avi", fourcc, 30, (530, 476))
  
  
  
  for frame in frames:
  
      <do stuff="stuff" to="to" generate="generate" foo="foo">
  
      cv2.imshow("foo", foo)
  
      vidout.write(foo)
  
  vidout.release()
  
  </do>

  Verified shape, dtype, and general viability of output data with cv2.imshow("foo", foo)

  Results : Unplayable AVI files

• ffmpeg concatenate two videos, unexpectedly changes the first second(s) of 2nd video

  29 juin 2019, par Roy

  I used ffmpeg to concatenate two videos of my game play recordings. I wrote a list.txt file which lists the two files :

  list.txt:
  
  file 2019~06~28_~_Game_1_~_Part_2.mp4
  
  file 2019~06~28_~_Game_1_~_Part_3.mp4

  I then run ffmpeg to concat them :

  ffmpeg -safe 0 -f concat -i list.txt -c copy "output.mp4"

  However, the resulting video seems to be skipping frames (or going through them really quickly) at the first second(s) of the second video, causing the perception of the motion suddenly fast-forwarded.

  The two videos were recorded by the same game video recorder "GeForce Experience" in one game session. They should match smoothly when concatenated.

  Here is the output of ffmpeg :

  ffmpeg version 3.4.1 Copyright (c) 2000-2017 the FFmpeg developers
  
    built with gcc 7.2.0 (GCC)
  
    configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-bzlib --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-cuda --enable-cuvid --enable-d3d11va --enable-nvenc --enable-dxva2 --enable-avisynth --enable-libmfx
  
    libavutil      55. 78.100 / 55. 78.100
  
    libavcodec     57.107.100 / 57.107.100
  
    libavformat    57. 83.100 / 57. 83.100
  
    libavdevice    57. 10.100 / 57. 10.100
  
    libavfilter     6.107.100 /  6.107.100
  
    libswscale      4.  8.100 /  4.  8.100
  
    libswresample   2.  9.100 /  2.  9.100
  
    libpostproc    54.  7.100 / 54.  7.100
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 000001600bbdb5e0] Auto-inserting h264_mp4toannexb bitstream filter
  
  Input #0, concat, from 'list.txt':
  
    Duration: N/A, start: 0.000000, bitrate: 24674 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, smpte170m/smpte170m/bt470m), 1920x1080 [SAR 1:1 DAR 16:9], 24479 kb/s, 59.69 fps, 60 tbr, 90k tbn, 120 tbc
  
      Metadata:
  
        creation_time   : 2019-06-29T04:43:18.000000Z
  
        handler_name    : VideoHandle
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 195 kb/s
  
      Metadata:
  
        creation_time   : 2019-06-29T04:43:18.000000Z
  
        handler_name    : SoundHandle
  
  File 'output.mp4' already exists. Overwrite ? [y/N] y
  
  Output #0, mp4, to 'output.mp4':
  
    Metadata:
  
      encoder         : Lavf57.83.100
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, smpte170m/smpte170m/bt470m), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 24479 kb/s, 59.69 fps, 60 tbr, 90k tbn, 90k tbc
  
      Metadata:
  
        creation_time   : 2019-06-29T04:43:18.000000Z
  
        handler_name    : VideoHandle
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 195 kb/s
  
      Metadata:
  
        creation_time   : 2019-06-29T04:43:18.000000Z
  
        handler_name    : SoundHandle
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
    Stream #0:1 -> #0:1 (copy)
  
  Press [q] to stop, [?] for help
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 000001600bbdb5e0] Auto-inserting h264_mp4toannexb bitstream filter
  
  frame= 7405 fps=0.0 q=-1.0 Lsize=  221175kB time=00:02:03.63 bitrate=14655.4kbits/s speed= 157x
  
  video:218137kB audio:2862kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.079741%

  In particular, I don’t know what does "Auto-inserting h254_mp4toannexb bitstream filter" mean. Did this caused the unexpected change ?

• capturing x11grab display from ffmpeg giveing "segmentation fault1 q=0.0"

  26 juin 2019, par user2369563

  In Debian 9, I am trying to record screen using ffmpeg over x11grab. it's working great but sometimes its give error as shown below.
Any idea what causing this ?

  



  exec error: Error: Command failed: ffmpeg -y  -f x11grab -s 1920x1080 -framerate 30 -i :1.0+0,0 -vsync 1 -c:v libx264 -preset ultrafast -crf 0 -pix_fmt yuv444p output.mkv
ffmpeg version 3.2.14-1~deb9u1 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 6.3.0 (Debian 6.3.0-18+deb9u1) 20170516
  configuration: --prefix=/usr --extra-version='1~deb9u1' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libebur128 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
  libavutil      55. 34.101 / 55. 34.101
  libavcodec     57. 64.101 / 57. 64.101
  libavformat    57. 56.101 / 57. 56.101
  libavdevice    57.  1.100 / 57.  1.100
  libavfilter     6. 65.100 /  6. 65.100
  libavresample   3.  1.  0 /  3.  1.  0
  libswscale      4.  2.100 /  4.  2.100
  libswresample   2.  3.100 /  2.  3.100
  libpostproc    54.  1.100 / 54.  1.100
[x11grab @ 0x55f87adcffa0] Stream #0: not enough frames to estimate rate; consider increasing probesize
Input #0, x11grab, from ':1.0+0,0':
  Duration: N/A, start: 1561540173.584858, bitrate: N/A
    Stream #0:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 1920x1080, 30 fps, 1000k tbr, 1000k tbn, 1000k tbc
[libx264 @ 0x55f87adda860] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
[libx264 @ 0x55f87adda860] profile High 4:4:4 Predictive, level 4.0, 4:4:4 8-bit
[libx264 @ 0x55f87adda860] 264 - core 148 r2748 97eaef2 - H.264/MPEG-4 AVC codec - Copyleft 2003-2016 - http://www.videolan.org/x264.html - options: cabac=0 ref=1 deblock=0:0:0 analyse=0:0 me=dia subme=0 psy=0 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=0 chroma_qp_offset=0 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=250 keyint_min=25 scenecut=0 intra_refresh=0 rc=cqp mbtree=0 qp=0
Output #0, matroska, to 'output.mkv':
  Metadata:
    encoder         : Lavf57.56.101
    Stream #0:0: Video: h264 (libx264) (H264 / 0x34363248), yuv444p, 1920x1080, q=-1--1, 30 fps, 1k tbn, 30 tbc
    Metadata:
      encoder         : Lavc57.64.101 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
Press [q] to stop, [?] for help
Segmentation fault1 q=0.0 size=   10942kB time=00:00:02.40 bitrate=37332.4kbits/s speed=0.923x