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• 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.

• avcodec/exif : avoid allocation failure on empty EXIF metadata

  24 août, par Leo Izen

  avcodec/exif : avoid allocation failure on empty EXIF metadata
  An EXIF IFD with 0 entries is legal, but does not contain metadata. We
  
  should not attempt to allocate a struct with size zero in this case, as
  
  this causes an allocation failure. Instead, we just leave the struct
  
  empty.
  Fixes : #20305.
  Signed-off-by : Leo Izen <leo.izen@gmail.com>
  

  • [DH] libavcodec/exif.c

• FFMPEG / FFMPLAY readvitc in Python or C#

  23 février 2021, par Sérgio Herculano

  I have the ffplay command below that read a file with VITC timecode and display timecode information in the screeen.

  


  ffplay -vf "readvitc=scan_max=45,crop=iw:16:0:0,scale=1440:16:flags=neighbor,setdar=90/1,drawtext=fontfile=C\\:/windows/Fonts/arial.ttf:fontcolor=yellow:fontsize=12:box=1:boxcolor=black@0.5:x=(w-tw)/2:y=h*3/4-ascent:text=VITC %{metadata\\\:lavfi.readvitc.tc_str\\\:-- -- -- --}" ./TC_01_10_00_00.mp4


  


  When I run it in Windows it is displaying timecode information correctly, my question is how can I write a program in Python in order to get this VITC timecode information and use this as a variable ?

  


  Anyone knows a way to do that ?

  


  Thanks in advance.