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• avdevice/decklink : remove pthread dependency

  15 avril 2017, par Aaron Levinson

  avdevice/decklink : remove pthread dependency
  Purpose : avdevice/decklink : Removed pthread dependency by replacing
  
  semaphore used in code appropriately.  Doing so makes it easier to
  
  build ffmpeg using Visual C++ on Windows.  This is a contination of
  
  Kyle Schwarz's "avdevice/decklink : Remove pthread dependency" patch
  
  that is available at https://patchwork.ffmpeg.org/patch/2654/ .  This
  
  patch wasn't accepted, and as far as I can tell, there was no
  
  follow-up after it was rejected.
  Notes : Used Visual Studio 2015 (with update 3) for this.
  Comments :
  — configure : Eliminated pthreads dependency for decklink_indev_deps
  
     and decklink_outdev_deps and replaced with threads dependency
  — libavdevice/decklink_common.cpp / .h :
  
  a) Eliminated semaphore and replaced with a combination of a mutex,
  
     condition variable, and a counter (frames_buffer_available_spots).
  
  b) Removed include of pthread.h and semaphore.h and now using
  
     libavutil/thread.h instead.
  — libavdevice/decklink_dec.cpp : Eliminated include of pthread.h and
  
     semaphore.h.
  — libavdevice/decklink_enc.cpp :
  
  a) Eliminated include of pthread.h and semaphore.h.
  
  b) Replaced use of semaphore with the equivalent using a combination
  
     of a mutex, condition variable, and a counter
  
     (frames_buffer_available_spots).  In theory, libavutil/thread.h and
  
     the associated code could have been modified instead to add
  
     cross-platform implementations of the sem_ functions, but an
  
     inspection of the ffmpeg source base indicates that there are only
  
     two cases in which semaphores are used (including this one that was
  
     replaced), so it was deemed to not be worth the effort.
  Signed-off-by : Marton Balint <cus@passwd.hu>
  

  • [DH] configure
  • [DH] libavdevice/decklink_common.cpp
  • [DH] libavdevice/decklink_common.h
  • [DH] libavdevice/decklink_dec.cpp
  • [DH] libavdevice/decklink_enc.cpp

• mkv file progressively out of sync

  29 avril 2017, par Piruzzolo

  I have a bunch of mkv files, with FLAC as the audio codec and FFV1 as the video one.

  The files were created using an EasyCap acquisition dongle from a VCR analog source. Specifically, I used VLC’s "open acquisition device" prompt and selected PAL. Then, I converted the files (audio PCM, video raw YUV) to (FLAC, FFV1) using

  ffmpeg.exe -i input.avi -acodec flac -vcodec ffv1 -level 3 -threads 4 -coder 1 -context 1 -g 1 -slices 24 -slicecrc 1 output.mkv

  Now, the files are progressively out of sync. It may due to the fact that while (maybe) the video has a constant framerate, the FLAC track has variable framerate. So, is there a way to sync the track to audio, or something alike ? Can FFmpeg do this ? Thanks

  EDIT

  On Mulvya hint, I plotted the difference in sync at various times ; the first column shows the seconds elapsed, the second shows the difference - in secs. The plot seems to behave linearly, with 0.0078 as a constant slope. NOTE : measurements taken by hands, by means of a chronometer

  

  EDIT 2

  Playing around with VirtualDub, I found that changing the framerate to 25 fps from the original 24.889 (Video->Frame rate...->Change frame rate to) and using the track converted to wav definitely does work. Two problems, though : VirtualDub crashes when importing the original FFV1-FLAC mkv file, so I had to convert the video to H264 to try it out ; more, I find it difficult to use an external encoder to save VirtualDub output.

  So, could I avoid using VirtualDub, and simply use ffmpeg for it ? Here’s the exported vdscript :

      VirtualDub.audio.SetSource("E:\\Cassette\\Filmini\\masters\\Cassetta 4_track2_ita.wav", "");
  
      VirtualDub.audio.SetMode(0);
  
      VirtualDub.audio.SetInterleave(1,500,1,0,0);
  
      VirtualDub.audio.SetClipMode(1,1);
  
      VirtualDub.audio.SetEditMode(1);
  
      VirtualDub.audio.SetConversion(0,0,0,0,0);
  
      VirtualDub.audio.SetVolume();
  
      VirtualDub.audio.SetCompression();
  
      VirtualDub.audio.EnableFilterGraph(0);
  
      VirtualDub.video.SetInputFormat(0);
  
      VirtualDub.video.SetOutputFormat(7);
  
      VirtualDub.video.SetMode(3);
  
      VirtualDub.video.SetSmartRendering(0);
  
      VirtualDub.video.SetPreserveEmptyFrames(0);
  
      VirtualDub.video.SetFrameRate2(25,1,1);
  
      VirtualDub.video.SetIVTC(0, 0, 0, 0);
  
      VirtualDub.video.SetCompression();
  
      VirtualDub.video.filters.Clear();
  
      VirtualDub.audio.filters.Clear();

  The first line imports the wav-converted audio track.
  Can I set an equivalent pipe in ffmpeg (possibly, using FLAC - not wav) ? SetFrameRate2 is maybe the key, here.

• h264_sei : Add namespace prefix to all SEI values

  15 mai 2017, par Mark Thompson

  h264_sei : Add namespace prefix to all SEI values
  This avoids confusion with equivalent H.265 SEI values when both are
  
  being used at the same time.
  

  • [DBH] libavcodec/h264_parser.c
  • [DBH] libavcodec/h264_sei.c
  • [DBH] libavcodec/h264_sei.h
  • [DBH] libavcodec/h264_slice.c
  • [DBH] libavcodec/vaapi_encode_h264.c