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• Files created with a direct stream copy using FFmpeg's libavformat API play back too fast at 3600 fps

  2 octobre 2013, par Chris Ballinger

  I am working on a libavformat API wrapper that converts MP4 files with H.264 and AAC to MPEG-TS segments suitable for streaming. I am just doing a simple stream copy without re-encoding, but the files I produce play the video back at 3600 fps instead of 24 fps.

  Here are some outputs from ffprobe https://gist.github.com/chrisballinger/6733678, the broken file is below :

  r_frame_rate=1/1
  
  avg_frame_rate=0/0
  
  time_base=1/90000
  
  start_pts=0
  
  start_time=0.000000
  
  duration_ts=2999
  
  duration=0.033322

  The same input file manually sent through ffmpeg has proper timestamp information :

  r_frame_rate=24/1
  
  avg_frame_rate=0/0
  
  time_base=1/90000
  
  start_pts=126000
  
  start_time=1.400000
  
  duration_ts=449850
  
  duration=4.998333

  I believe the problem lies somewhere in my setup of libavformat here : https://github.com/OpenWatch/FFmpegWrapper/blob/master/FFmpegWrapper/FFmpegWrapper.m#L349 where I repurposed a bunch of code from ffmpeg.c that was required for the direct stream copy.

  Since 3600 seems like a "magic number" (60*60), it could be as simple as me not setting the time scale properly, but I can't figure out where my code diverges from ffmpeg/avconv itself.

  Similar question here, but I don't think they got as far as I did : Muxing a H.264 Annex B & AAC stream using libavformat with vcopy/acopy

• Revision d11221f433 : Improves constant qual, constrained qual turned on Adds modeled functions to de

  20 septembre 2013, par Deb Mukherjee

  Changed Paths :
   Modify /vp9/encoder/vp9_firstpass.c

  
   Modify /vp9/encoder/vp9_onyx_if.c

  
   Modify /vp9/vp9_cx_iface.c

  
  
  Improves constant qual, constrained qual turned on

  Adds modeled functions to decide the qp for altref frames in constant q
  mode similar to other functions in use in bitrate mode.

  Also turns on the constrained quality mode (end-usage=2) option which
  was turned off before. Basic testing shows the mode works in principle,
  to cap bitrate to the target-bitrate specified, while allowing lower
  bitrate depending on the cq-level specified. The mode will need to be
  improved over time.

  Results for constant quality vs bitrate control mode :
  derfraw300/fullderfraw : +3.0% at constant quality over bitrate control.
  fullstdhdraw : +4.341%
  stdhdraw250 : +5.361%

  Change-Id : If5027c9ec66c8e88d33e47062c6cb84a07b1cda9

• movie2avi - how to fix the frame size ?

  2 octobre 2013, par Ed Mendes

  I have searched stackoverflow for a similar question and I found question "movie2avi-frame-size-error-and-keeping-frame-size-constant". Unfortunately the answer given there did not solve my problem (it has been suggested the use of xlim, ylim and zlim).

  In what follows I send a lightly modified version of a well-known example given elsewhere.

  %# figure
  
  figure, set(gcf, 'Color','white')
  
  Z = peaks; surf(Z);  axis tight
  
  set(gca, 'nextplot','replacechildren', 'Visible','off');
  
  [az,el]=view;
  
  xl=xlim;
  
  yl=ylim;
  
  zl=zlim;
  
  
  
  %# preallocate
  
  nFrames = 20;
  
  mov(1:nFrames) = struct('cdata',[], 'colormap',[]);
  
  
  
  %# create movie
  
  for k=1:nFrames
  
     view([(az-k*10) el]);
  
     xlim(xl);ylim(yl);zlim(zl);
  
     drawnow;pause(0.1);
  
     mov(k) = getframe(gca);
  
  end
  
  close(gcf)
  
  
  
  %# save as AVI file, and open it using system video player
  
  movie2avi(mov, 'myPeaks1.avi', 'compression','None', 'fps',10);

  The idea is to rotate the figure and create a movie. Everything works fine except for the last command, that is, movie2avi. The error msg is

  Error using avifile/addframe>ValidateFrame (line 290)
  
  Frame must be 435 by 344.
  
  
  
  Error in avifile/addframe (line 158)
  
  ValidateFrame(aviobj,width, height,dims);
  
  
  
  Error in movie2avi (line 67)
  
  avimov = addframe(avimov,mov);
  
  
  
  Error in more_video_test (line 24)
  
  movie2avi(mov, 'myPeaks1.avi', 'compression','None', 'fps',10); 

  I have looked at approaches-to-create-a-video-in-matlab here in stackoverflow and found that :

  a) Solution ffmpeg works but I would like to avoid it.
  b) All other solutions failed even QTWriter. How can I fix the frame size so that all these other solutions work ?

  Many thanks.

  Ed