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• FFMpeg sws_scale Static and Shared Huge Performance Difference

  6 novembre 2018, par Ali

  I used swscale in my code as a shared library then managed to compile FFMpeg (4.1) to static libraries with Visual Studio with this command just to get swscale :

  ./configure --toolchain=msvc --arch=x86_32 --disable-everything --disable-programs 

  I have nasm and yasm installed. this my config output :

  install prefix            /usr/local
  
  source path               .
  
  C compiler                cl
  
  C library                 msvcrt
  
  ARCH                      x86 (generic)
  
  big-endian                no
  
  runtime cpu detection     yes
  
  standalone assembly       yes
  
  x86 assembler             nasm
  
  MMX enabled               yes
  
  MMXEXT enabled            yes
  
  3DNow! enabled            yes
  
  3DNow! extended enabled   yes
  
  SSE enabled               yes
  
  SSSE3 enabled             yes
  
  AESNI enabled             yes
  
  AVX enabled               yes
  
  AVX2 enabled              yes
  
  AVX-512 enabled           yes
  
  XOP enabled               yes
  
  FMA3 enabled              yes
  
  FMA4 enabled              yes
  
  i686 features enabled     yes
  
  CMOV is fast              no
  
  EBX available             no
  
  EBP available             no
  
  debug symbols             yes
  
  strip symbols             no
  
  optimize for size         no
  
  optimizations             yes
  
  static                    yes
  
  shared                    no
  
  postprocessing support    no
  
  network support           yes
  
  threading support         w32threads
  
  safe bitstream reader     yes
  
  texi2html enabled         no
  
  perl enabled              no
  
  pod2man enabled           no
  
  makeinfo enabled          no
  
  makeinfo supports HTML    no
  
  
  
  External libraries:
  
  schannel
  
  
  
  External libraries providing hardware acceleration:
  
  d3d11va                    dxva2
  
  
  
  Libraries:
  
  avcodec                    avdevice                   avfilter                   avformat                   avutil                     swresample                 swscale
  
  
  
  Programs:
  
  Enabled decoders:
  
  Enabled encoders:
  
  Enabled hwaccels:
  
  Enabled parsers:
  
  Enabled demuxers:
  
  Enabled muxers:
  
  Enabled protocols:
  
  Enabled filters:
  
  Enabled bsfs:
  
  null
  
  Enabled indevs:
  
  Enabled outdevs:

  This compiled successfully and I replaced the lib files with .a file in QT :

  INCLUDEPATH += $$PWD/ffmpeg/inc/
  
  LIBS += $$files($$PWD/ffmpeg/lib/*.a, true)

  I didn’t change anything else. EXE works correctly without dependency but problem is static swscale is so much slower than the shared one. For 1080p share .DLL takes 2ms to shrink and convert yuv to rgb and static .A takes 6ms to

  I also tried removing --disable-everything --disable-programs but still the same. I want to know if it’s because of the cl compiler or I missed a library or a setting ?

  BTW this my system : Win10/i7 4820K/16GB/GTX970

  EDIT :

  I got this in app output :
  No accelerated colorspace conversion found from yuv420p to bgra.
  Although x86 folder in swscale is compiled, it seems it’s not linked in the output.

• How to split video into parts audio/video/text in one command ?

  22 novembre 2020, par lockwise

  I have one video file .mkv.
Inside this file, there is a video track, 3 audio tracks, 2 subtitles, a poster file, and a backdrop file.
Does ffmpeg know how to split .mkv into separate parts, video / 3 audio / 2 subtitles ?

  


  ~# ffmpeg -hide_banner -i input.mkv
Input #0, matroska,webm, from 'input.mkv':
  Duration: 01:37:03.90, start: 0.000000, bitrate: 3605 kb/s
    Metadata:
      title           : 01:33:51.582
    Stream #0:0(eng): Video: h264 (High), yuv420p(tv, bt709, progressive), 1024x576 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default)
    Metadata:
      title           : Video
    Stream #0:1(rus): Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s (default)
    Metadata:
      title           : MVO «West Video»
    Stream #0:2(spa): Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s
    Metadata:
      title           : MVO Spain-1
    Stream #0:3(eng): Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s
    Metadata:
      title           : MVO TRK
    Stream #0:4(eng): Subtitle: subrip (default)
    Metadata:
      title           : RUS
    Stream #0:5(eng): Subtitle: subrip
    Metadata:
      title           : Eng
    Stream #0:6(und): Video: mjpeg (Progressive), yuvj420p(pc, bt470bg/unknown/unknown), 780x1170 [SAR 1:1 DAR 2:3], 90k tbr, 90k tbn, 90k tbc (attached pic)
    Metadata:
      filename        : poster.jpg
      mimetype        : image/jpeg
      title           : poster
      LANGUAGE        : und
    Stream #0:7(und): Video: mjpeg (Progressive), yuvj420p(pc, bt470bg/unknown/unknown), 1280x719 [SAR 1:1 DAR 1280:719], 90k tbr, 90k tbn, 90k tbc (attached pic)
    Metadata:
      filename        : backdrop.jpg
      mimetype        : image/jpeg
      title           : backdrop
      LANGUAGE        : und


  


  I need :

  


  

  • Video

    

    • input0.mp4

    


    


  


  • Audio

    

    • input0.m4a

    


    • input1.m4a

    


    • input2.m4a

    


    


  


  • Subtitle

    

    • input0.vtt

    


    • input1.vtt

    


    


  


  


  These commands do the splitting, but I need to know exactly how many audio files and how many subtitle files are in the mkv.

  


  ffmpeg -y -i input.mkv \
  -map 0:v:0 -c:v libx264 output0.mp4


  


  ffmpeg -y -i input.mkv \
  -map 0:a:0 -c:a aac output0.m4a \
  -map 0:a:1 -c:a aac output1.m4a \
  -map 0:a:2 -c:a aac output2.m4a


  


  ffmpeg -y -i input.mkv \
  -map 0:s:0 output0.vtt \
  -map 0:s:1 output1.vtt


  


  Is it possible to make such divisions without knowing the file number 0:a:2, 0:s:1 ?

  


• Why process output reader returns null data ? When same code in other process works correct

  26 août 2019, par Владимир Водов

  I try to get output from ffmpeg process but cant get output.
  In another processes and commands it works correctly but output returns immideately when start !

          using (var process = new Process())
  
          {
  
              process.StartInfo = new ProcessStartInfo()
  
              {
  
                  FileName = LinkHelper.IPFS_PATH,
  
                  Arguments = cmd,
  
                  UseShellExecute = false,
  
                  CreateNoWindow = true,
  
                  RedirectStandardOutput = true
  
              };
  
  
  
              process.ErrorDataReceived += FfmpegErrorRecieved;
  
              process.Start();
  
  
  
              using (StreamReader reader = process.StandardOutput)
  
              {
  
                  string output = await reader.ReadToEndAsync();
  
                  Console.WriteLine(output);
  
              }               
  
              process.WaitForExit();
  
          }

  Before output handle !

  Update :
  As szatmary said ffmpeg use output error instead standard output, so when you initialize process.StandartInfo don’t forget initialize property "RedirectStandardError" to TRUE !

  Here is correct code :

  private async Task DetectFFmpegCamerasAsync()
  
      {
  
          var cmd = "-list_devices true -f dshow -i dummy";
  
          using (var process = new Process())
  
          {
  
              process.StartInfo = new ProcessStartInfo()
  
              {
  
                  FileName = LinkHelper.FFMPEG_PATH,
  
                  Arguments = cmd,
  
                  UseShellExecute = false,
  
                  CreateNoWindow = true,
  
                  RedirectStandardError = true
  
              };
  
  
  
              process.Start();
  
  
  
              using (StreamReader reader = process.StandardError)
  
              {
  
                  string output = await reader.ReadToEndAsync();
  
                  Console.WriteLine($"Camera detection output: \n {output}");
  
              }               
  
              process.WaitForExit();
  
          }
  
      }