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• avcodec/ppc/mpegvideo_altivec : Don't process coeffs as scalars

  22 mars, par Andreas Rheinhardt

  avcodec/ppc/mpegvideo_altivec : Don't process coeffs as scalars
  block_last_index and nCoeffs is an optimization designed
  
  to avoid processing unnecessarily many coefficients ; yet
  
  it would be legal to always process all coefficients
  
  (all coefficients beyond nCoeffs are zero anyway and
  
  zeros are always unquantized to zeros). Therefore
  
  one does not need a scalar tail.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/ppc/mpegvideo_altivec.c

• Why do I get different codecs on Windows and Linux with same code ?

  27 janvier 2016, par user3277340

  I am using the API version of FFMPEG to generate a MP4 file from a series of images. I specify the output by calling

  AVFormatContext *oc = NULL ;
  avformat_alloc_output_context2 (&oc,NULL,"mp4",NULL) ;

  Running the exact same code on Windows and Linux I get different codecs assigned. On Windows, the value of oc->oformat->video_code is AV_CODEC_ID_H264 (28), but on Linux I get AV_CODEC_ID_MPEG4.

  I tracked this down because on Windows my calls to avcodec_encode_video2(.,.,.,&got_packet) were always returning got_packet=0 so I never called av_interleaved_write_frame. I added a NULL AVFrame at the end to flush the video. But it was very small and did not contain the images I expected to see there.

  But on Linux everything worked just fine. So I went ahead and manually changed the value of oc->oformat->video_code and I got the expected results.

  My questions :

  1) Why do I get different codec types on different platforms with the same code ? Is there a parameter I need to set to force MPEG4 ?

  2) Is it "legal" to change this parameter after the call to avformat_alloc_output_context2 ? My concern is that "oc" has been properly initialized and, with the change, something may be inconsistent.

  3) Is there a way to force the MPEG4 codec on any machine ?

  Thanks.

• Use popen with a relative or absolute path on Windows in C

  9 juillet 2017, par Tiwenty

  I’m trying to a GUI wrapper for FFmpeg. I decided to build my program around the binary instead of the libraries. I want to call ffmpeg.exe in parallel to my program and get the console output instantly to parse it and show to the user a progress bar or something.

  So I found popen which sends me the output when it comes so I can do what I want with it. But there are some problems with paths in popen on Windows.

  When I try ffmpeg.exe -i TEST.mkv TEST.mp4 (when I’m in the folder of both ffmpeg.exe and my source file either from start or a chdir) it works well and I get what I want.

  But when I do

  bin/ffmpeg.exe -i TEST.mkv TEST.mp4

  (with the executable obviously being in the bin folder) it doesn’t find the command bin :

  'bin' is not recognized as an internal or external command, operable program or batch file.

  It also doesn’t work with quotation marks around the path :

  "bin/ffmpeg.exe" -i TEST.mkv TEST.mp4

  But it does work with an absolute path and quotation marks :

  "C:/PATH/TO/USER/FFmpeg GUI/bin/ffmpeg.exe" -i jellyfish.mkv jellyfish.mp4.

  But it gets funnier.

  If I use relative paths for the source and output, it works.

  "C:/Users/tibtw_000/Raccourci/Code/FFmpeg GUI/bin/ffmpeg.exe" -i videos/jellyfish.mkv videos/jellyfish.mp4

  But if I want to put an absolute path to my source or output files, it now doesn’t work.

  "C:/PATH/TO/USER/FFmpeg GUI/bin/ffmpeg.exe" -i "C:/PATH/TO/USER/FFmpeg GUI/videos/jellyfish.mkv"

  and now returns

  'C:/PATH/TO/USER/FFmpeg' is not recognized as an internal or external command, operable program or batch file.

  Now I’m starting to wonder if the space in my path is at fault. And it was. When I use

  C:/PATH/TO/USER/FFmpegGUI/bin/ffmpeg.exe -i C:/PATH/TO/USER/FFmpegGUI/videos/jellyfish.mkv C:/PATH/TO/USER/FFmpegGUI/videos/jellyfish.mp4 in popen everything works perfectly.

  So what should I do ? Do I force the user to not put his files in paths with spaces ? Is there a special character that I can put instead of a normal space in the path to make popen understand what I want it to do ?