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• How to encode bmp images to H264, H265 losslessly with and without Nvenc

  26 août 2020, par Hamza Ghizaoui

  So, let s assume that i have 5000 BMP images (1920x1080) that i want to encode into a video.

  


  I managed to do that losslessly using FFMPEG using the following 4 encoders :

  


  

  • libx264

  


  • libx265

  


  • h264_nvenc

  


  • hevc_nvenc

  


  


  The problem is that when i try to test my results using PSNR, i get extremly high values, in the 30-70 range. What is happening ?
Is the problem with color space conversion ? (None of the encoders above seem to support RGB, a conversion to YUV occur and I m assuming that a lot of averaging is happening. stuff that PSNR test is very sensetive toward).

  


  If my reasoning is correct, is it possible to encode BMP 100% losslessly. the resuling video will be streamed locally. the network is 10 GBS, so the size isn t that important.

  


  thank you

  


• Error opening filters : Running ffmpeg through Groovy and ProcessBuilder

  30 octobre 2016, par smeeb

  This question involves the popular Linux media processing utility "ffmpeg", but I think its really a Java 8 ProcessBuilder question at its core. Or possibly an issue w/ Groovy GStrings.

  The ffmpeg command to split an MP4 video into frames/images based on a sampling rate is :

  ffmpeg -i /some/path/to/video.mp4 -vf "select=not(mod(n\,${samplingRate}))" -vsync vfr -q:v 2 img_%d.jpg

  Where ${samplingRate} is a positive integer and represents the number of frames to skip in between creating each frame. So for instance, if you had a video with 430 frames in it, and wanted to sample every 50th frame, your command would be :

  ffmpeg -i /some/path/to/video.mp4 -vf "select=not(mod(n\,50))" -vsync vfr -q:v 2 img_%d.jpg

  Which would then create 8 (or maybe 9, not gonna do the math for a pretend example) JPG files called img_1.jpg, img_2.jpg, ...etc. The first image would be the 50th frame in the video. The second image would be the 100th frame, etc. I have ran the above command directly from a terminal and confirmed that it is correct and succeeds without errors.

  I have a Groovy app, and am trying to run this ffmpeg command via a Java 8 ProcessBuilder, and am having issues with the select= argument. Currently I have :

  int numSamples = 50
  
  Process frameSamplerProc = new ProcessBuilder(
  
      'ffmpeg',
  
      '-i',
  
      "/home/myuser/some/path/to/video.mp4",
  
      '-vf',
  
      "\"select=not(mod(n\\,${numSamples}))\"",
  
      '-vsync',
  
      'vfr',
  
      '-q:v',
  
      '2',
  
      'sample%d.jpg'
  
  ).redirectErrorStream(true).start()
  
  
  
  frameSamplerProc.inputStream.eachLine { fsamplerLine ->
  
      println(fsamplerLine)
  
  }

  When I run thise code, I don’t get any errors, but I do see errors in ffmpeg’s output :

  ffmpeg version N-81995-gd790e48 Copyright (c) 2000-2016 the FFmpeg developers
  
  // Omitting the next ~50 lines of output as it all looks normal
  
  
  
  Metadata:
  
    creation_time   : 2016-10-27T20:20:01.000000Z
  
    handler_name    : SoundHandle
  
  [AVFilterGraph @ 0x3eddc80] No such filter: '"select'
  
  Error opening filters!

  I’m wondering if I’m not escaping the select argument properly or if I’m passing in a bad array to the ProcessBuilder. Can anybody spot where I’m going awry ?

• How to call ffmpeg code to keep same video quality ?

  7 mai 2016, par seaguest

  I am using ffmpeg3 to convert mv.webm to mp4, it works fine when I use the command line.

  $ ffprobe mv.webm 
  
  ffprobe version N-79789-g58b3e56 Copyright (c) 2007-2016 the FFmpeg developers
  
    built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.1)
  
    configuration: --enable-gpl --enable-shared --enable-libx264
  
    libavutil      55. 24.100 / 55. 24.100
  
    libavcodec     57. 39.100 / 57. 39.100
  
    libavformat    57. 36.100 / 57. 36.100
  
    libavdevice    57.  0.101 / 57.  0.101
  
    libavfilter     6. 45.100 /  6. 45.100
  
    libswscale      4.  1.100 /  4.  1.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, matroska,webm, from 'mv.webm':
  
    Metadata:
  
      encoder         : google
  
    Duration: 00:04:56.36, start: 0.000000, bitrate: 836 kb/s
  
      Stream #0:0: Video: vp8, yuv420p, 640x480, SAR 1:1 DAR 4:3, 25 fps, 25 tbr, 1k tbn (default)
  
      Stream #0:1: Audio: vorbis, 44100 Hz, stereo, fltp (default)
  
  
  
  $ ffmpeg -i mv.webm  -acodec aac -vcodec libx264  mv1.mp4
  
  $ ffprobe mv1.mp4 
  
  ffprobe version N-79789-g58b3e56 Copyright (c) 2007-2016 the FFmpeg developers
  
    built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.1)
  
    configuration: --enable-gpl --enable-shared --enable-libx264
  
    libavutil      55. 24.100 / 55. 24.100
  
    libavcodec     57. 39.100 / 57. 39.100
  
    libavformat    57. 36.100 / 57. 36.100
  
    libavdevice    57.  0.101 / 57.  0.101
  
    libavfilter     6. 45.100 /  6. 45.100
  
    libswscale      4.  1.100 /  4.  1.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'n1.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.36.100
  
    Duration: 00:04:56.36, start: 0.000000, bitrate: 628 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x480 [SAR 1:1 DAR 4:3], 500 kb/s, 25 fps, 25 tbr, 12800 tbn (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 120 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler

  I play it with VLC, there is no noise at all.

  Here is my first question, in case we don’t specify the bitrate in the ffmpeg command, how are the bitrate of video/audio determined ?

  Since I am developping in Golang, I use the framework gmf which calls ffmpeg, I use go to convert the video format without specifying bitrate, then I got the following info :

  $ ffprobe mv2.mp4 
  
  ffprobe version N-79789-g58b3e56 Copyright (c) 2007-2016 the FFmpeg developers
  
    built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.1)
  
    configuration: --enable-gpl --enable-shared --enable-libx264
  
    libavutil      55. 24.100 / 55. 24.100
  
    libavcodec     57. 39.100 / 57. 39.100
  
    libavformat    57. 36.100 / 57. 36.100
  
    libavdevice    57.  0.101 / 57.  0.101
  
    libavfilter     6. 45.100 /  6. 45.100
  
    libswscale      4.  1.100 /  4.  1.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'mv2.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.36.100
  
    Duration: 00:04:56.36, start: 0.000000, bitrate: 540 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x480, 385 kb/s, 25 fps, 25 tbr, 12800 tbn (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 147 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler

  The bitrate is event better than mv1.mp4, however when I play it with VLC, I heard a lot of noises.

  I tried to increase the audio bitrate (the way we set bitrate is like AVCodecContext->bit_rate = 441000...), but this doesn’t help.

  Maybe there is some option that I need to add when calling ffmpeg code to keep the same quality as input source, could anyone help ?