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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 ?

• ffmpeg itsoffset doesnt apply offset to mp4

  26 juillet 2019, par brux

  The following command mixes an mp4 and an mp3 together, keeping the audio from the mp4.

  ffmpeg -i video.mp4 -i audio.mp3 -map 0:v -c:v copy -filter_complex '[0:a][1:a]amix[aout]' -map '[aout]' -shortest out.mp4

  The command works as expected.

  Now I want to offset the mp4 file (both the audio and video stream of the mp4) so that there is a delay of 500ms at the start of the mp4, here is my command :

  ffmpeg -itsoffset 00:00:00.500 -i video.mp4 -i audio.mp3 -map 0:v -c:v copy -filter_complex '[0:a][1:a]amix[aout]' -map '[aout]' -shortest out.mp4

  This doesnt work as expected, the output doesnt have the expected delay of 500ms at the start of the mp4 streams. It appears the output is just the same as the first command I ran.

  The version of ffmpeg I am using is :

  ffmpeg version n4.0-39-gda39990

  Here are the files I’m using :

  video.mp4

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/storage/emulated/0/video.mp4':
  
        Metadata:
  
          major_brand     : mp42
  
          minor_version   : 0
  
          compatible_brands: isommp42
  
          creation_time   : 2019-07-26T03:28:49.000000Z
  
          com.android.version: 8.0.0
  
        Duration: 00:00:07.64, start: 0.000000, bitrate: 20534 kb/s
  
          Stream #0:0(eng): Video: h264 (avc1 / 0x31637661), yuvj420p(pc, smpte170m), 1920x1080, 20966 kb/s, SAR 1:1 DAR 16:9, 29.70 fps, 29.75 tbr, 90k tbn, 180k tbc (default)
  
          Metadata:
  
            rotate          : 270
  
            creation_time   : 2019-07-26T03:28:49.000000Z
  
            handler_name    : VideoHandle
  
          Side data:
  
            displaymatrix: rotation of 90.00 degrees
  
          Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 96 kb/s (default)
  
          Metadata:
  
            creation_time   : 2019-07-26T03:28:49.000000Z
  
            handler_name    : SoundHandle

  audio.mp3

  Input #0, mp3, from '/storage/emulated/0/audio.mp3':
  
        Metadata:
  
          album           : Sunflower (Spider-Man: Into the Spider-Verse) - Single
  
          composer        : Louis Bell, Carter Lang, Austin Richard Post, Billy Walsh & Khalif Malik Ibin Shaman Brown
  
          genre           : Hip-Hop/Rap
  
          copyright       : This Compilation ℗ 2018 Republic Records, a division of UMG Recordings, Inc.
  
          title           : Sunflower (Spider-Man: Into the Spider-Verse)
  
          artist          : Post Malone & Swae Lee
  
          album_artist    : Post Malone & Swae Lee
  
          track           : 01/01
  
          TYER            : 2018-10-18T07:00:00Z
  
        Duration: 00:02:38.07, start: 0.000000, bitrate: 325 kb/s
  
          Stream #0:0: Audio: mp3, 44100 Hz, stereo, fltp, 320 kb/s
  
          Stream #0:1: Video: mjpeg, yuvj444p(pc, bt470bg/unknown/unknown), 1400x1400 [SAR 300:300 DAR 1:1], 90k tbr, 90k tbn, 90k tbc
  
          Metadata:
  
            comment         : Cover (front)