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• Convert Black to Transparency in FFMPEG

  12 février 2019, par Kapitano

  I have a sequence of BMP images, which I’m concatenating to an MPNG video file, with this FFMPEG code :

  ffmpeg -f image2 -framerate 12 -i "Frame_%d.bmp" -c:v png "Video.avi"

  I want to replace all black pixels with a transparency in the alpha layer, so it can be laid over other videos in an editor. The following code doesn’t work :

  ffmpeg -f image2 -framerate 12 -i "Frame_%d.bmp" -filter_complex "[0:v]colorkey=0x000000:0.01:0.0[BlackToTransparancy]" -map [BlackToTransparancy] -c:v png "Video.avi"

  As requested, here’s the full log :

  ffmpeg version N-93020-g3224d6691c Copyright (c) 2000-2019 the FFmpeg developers
  
    built with gcc 8.2.1 (GCC) 20181201
  
    configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --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. 26.100 / 56. 26.100
  
    libavcodec     58. 44.100 / 58. 44.100
  
    libavformat    58. 26.100 / 58. 26.100
  
    libavdevice    58.  6.101 / 58.  6.101
  
    libavfilter     7. 48.100 /  7. 48.100
  
    libswscale      5.  4.100 /  5.  4.100
  
    libswresample   3.  4.100 /  3.  4.100
  
    libpostproc    55.  4.100 / 55.  4.100
  
  Input #0, image2, from 'D:\ReadOut_Process\Test\Test__Frame_%d.bmp':
  
    Duration: 00:00:16.83, start: 0.000000, bitrate: N/A
  
      Stream #0:0: Video: bmp, bgra, 1280x720, 12 tbr, 12 tbn, 12 tbc
  
  Stream mapping:
  
    Stream #0:0 (bmp) -> colorkey
  
    colorkey -> Stream #0:0 (png)
  
  Press [q] to stop, [?] for help
  
  Output #0, avi, to 'D:\ReadOut_Process\Test\Test__Scribe.avi':
  
    Metadata:
  
      ISFT            : Lavf58.26.100
  
      Stream #0:0: Video: png (MPNG / 0x474E504D), rgba, 1280x720, q=2-31, 200 kb/s, 12 fps, 12 tbn, 12 tbc
  
      Metadata:
  
        encoder         : Lavc58.44.100 png
  
  frame=   34 fps=0.0 q=-0.0 size=     774kB time=00:00:02.16 bitrate=2924.7kbits/s speed=4.21x    
  
  frame=   65 fps= 64 q=-0.0 size=    1798kB time=00:00:04.75 bitrate=3100.1kbits/s speed=4.66x    
  
  frame=   95 fps= 62 q=-0.0 size=    3078kB time=00:00:07.25 bitrate=3477.4kbits/s speed=4.76x    
  
  frame=  124 fps= 61 q=-0.0 size=    4358kB time=00:00:09.66 bitrate=3692.8kbits/s speed=4.76x    
  
  frame=  155 fps= 61 q=-0.0 size=    6150kB time=00:00:12.25 bitrate=4112.4kbits/s speed=4.83x    
  
  frame=  185 fps= 61 q=-0.0 size=    7686kB time=00:00:14.75 bitrate=4268.5kbits/s speed=4.84x    
  
  frame=  202 fps= 58 q=-0.0 Lsize=    9187kB time=00:00:16.83 bitrate=4470.8kbits/s speed=4.83x    
  
  video:9176kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.112806%

  The BMPs are too large to upload, but here’s a link to a section of a typical one : https://pasteboard.co/I0RzfjI.bmp

  Can it be done ?

• FFmpeg auto rotate video when copying video stream without re-encoding

  25 février 2019, par Mahfujur Rahman

  I have been trying to convert an mp4 (portrait) file to mkv. As the mkv container support any video and audio stream, I am copying the audio and video stream to the output container. The command I’m using

  ffmpeg -y -i test.mp4 -vcodec copy -acodec copy test.mkv

  File info for test.mp4 is following

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test.mp4':
  
    Metadata:
  
      major_brand     : mp42
  
      minor_version   : 0
  
      compatible_brands: isommp42
  
      creation_time   : 2019-02-23T11:18:50.000000Z
  
      com.android.version: 8.0.0
  
    Duration: 00:00:25.86, start: 0.000000, bitrate: 12270 kb/s
  
      Stream #0:0(eng): Video: h264 (avc1 / 0x31637661), yuv420p(tv, bt709), 1280x720, 12005 kb/s, SAR 1:1 DAR 16:9, 30 fps, 30 tbr, 90k tbn, 180k tbc (default)
  
      Metadata:
  
        rotate          : 90
  
        creation_time   : 2019-02-23T11:18:50.000000Z
  
        handler_name    : VideoHandle
  
      Side data:
  
        displaymatrix: rotation of -90.00 degrees
  
      Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 256 kb/s (default)
  
      Metadata:
  
        creation_time   : 2019-02-23T11:18:50.000000Z
  
        handler_name    : SoundHandle

  Now, the problem is that the output video I get from ffmpeg is a 90 degree counter clockwise rotated video. The reason I believe is the following info being removed from output file,

  Side data:
displaymatrix: rotation of -90.00 degrees

  File info for rotated output file test.mkv

  Input #0, matroska,webm, from 'test.mkv':
  
    Metadata:
  
      MAJOR_BRAND     : mp42
  
      MINOR_VERSION   : 0
  
      COMPATIBLE_BRANDS: isommp42
  
      COM.ANDROID.VERSION: 8.0.0
  
      ENCODER         : Lavf58.12.100
  
    Duration: 00:00:25.87, start: 0.000000, bitrate: 12265 kb/s
  
      Stream #0:0(eng): Video: h264, yuv420p(tv, bt709, progressive), 1280x720, SAR 1:1 DAR 16:9, 30 fps, 30 tbr, 1k tbn, 2k tbc (default)
  
      Metadata:
  
        ROTATE          : 90
  
        HANDLER_NAME    : VideoHandle
  
        DURATION        : 00:00:25.866000000
  
      Stream #0:1(eng): Audio: aac, 48000 Hz, stereo, fltp (default)
  
      Metadata:
  
        HANDLER_NAME    : SoundHandle
  
        DURATION        : 00:00:25.813000000

  But when I convert this rotated output test.mkv to mp4 again, I get the portrait file. The displaymatrix side data appears again in the file info.

  Converting the same mp4 file to m4v by copying the steam works fine.

  So, this whole thing is very much confusing to me.

  Now my question is, how can I convert the mp4 file to mkv without re-encoding and avoid getting rotated output ?

  In this post they solved it for c++. I am working on android and using ffmpeg android wrapper to use the ffmpeg library. Is there any ffmpeg flag to handle this situation ?

• exec.Command error, no output to stdout or stderr

  19 février 2019, par n3wton

  I am trying to get the duration of a video using ffprobe and exec.Command but I keep getting an error. However, stdout and stderr are both empty so I don’t know what the problem is.

  func getVideoLength(filename string) float64 {
  
  cmd := exec.Command("ffprobe", "-i", filename, "-show_entries", "format=duration", "-v", "quiet", "-of", "csv=\"p=0\"")
  
  fmt.Println("ffprobe", "-i", filename, "-show_entries", "format=duration", "-v", "quiet", "-of", "csv=\"p=0\"")
  
      var out bytes.Buffer
  
      var stderr bytes.Buffer
  
      cmd.Stdout = &out
  
      cmd.Stderr = &stderr
  
      err := cmd.Run()
  
      if err != nil {
  
          fmt.Println("out: " + out.String())
  
          fmt.Println("stderr: " + stderr.String())
  
          log.Fatal(err)
  
      }
  
  
  
      length, err := strconv.ParseFloat(out.String(), 64)
  
      if err != nil {
  
          log.Fatal(err)
  
      }
  
  
  
  return length
  
  }

  Here is the output I get :

  ffprobe -i amelie.mp4 -show_entries format=duration -v quiet -of csv="p=0"
  
  out: 
  
  stderr: 
  
  2019/02/18 21:04:39 exit status 1

  not very helpful.

  Any ideas ?. Thanks.