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• Can't decode HEVC video with DXVA2 and ffmpeg

  10 mai 2018, par Igor

  I can’t use DXVA2 hardware acceleration for decoding of HEVC video with ffmpeg. DXVA2 for H.264 works fine.

  I compiled an official example hw_decode.c from ffmpeg sources :

  https://github.com/FFmpeg/FFmpeg/blob/master/doc/examples/hw_decode.c

  When I call av_send_packet() it performs a callback assigned in AVCodecContext->get_format and returns only AV_PIX_FMT_YUV420P for HEVC video instead of AV_PIX_FMT_DXVA2_VLD for all H.264 videos. So HW decoding doesn’t work.

  Software decoding of HEVC works without problems.

  MPC-HC plays fine HEVC video with DXVA2 (CPU loading is low and Task Manager shows work of Video decoder in GPU details). My video card is Geforce 1060.

• FFmpeg and file descriptors in Android Lollipop

  12 février 2015, par user3043703

  I’m going to use FFmpeg in an Android project as a JNI library and I know about the limitations of Kitkat. Since with the new release of Lollipop there is the possibility for third-party apps to access to external microsd I would like to exploit it. I’ve read this useful question so I use a ACTION_OPEN_DOCUMENT_TREE intent, the user chooses a folder and than I use a similar code to get a file descriptor. Then I send this UNIX file descriptor to a jni function. I’ve created a demo, if I use something like this :

  int descriptor = a_file_descriptor;
  
  FILE* fp = fdopen(descriptor , "w");
  
  fprintf(fp, "Hello from Lollipop!");
  
  fclose(fp);

  everything is fine. The problem is that I would like to extract the complete file name from the file descriptor. It’s possible with some tricks available for Linux but if I do an fopen and try to fprintf something in the file nothing happens. So I imagine I should use the file descriptor, but how to use it with FFmpeg ? I read about the pipe option but it seems for command line only. Thanks in advance for the help.

• Sync files timestamp with ffmpeg

  16 mars 2018, par Olivier Rivard

  I’m capturing video from 4 cameras connected with HDMI through a capture card. I’m using ffmpeg to save the video feed from the cameras to multiples jpeg files (30 jpeg per second per camera).

  I want to be able to save the images with the capture time. Currently I’m using this command for one camera :

  ffmpeg -f video4linux2 -pixel_format yuv420p -timestamps abs -I /dev/video0 -c:a jpeg -t 60 -ts_from_file 2 camera0-%5d.jpeg

  It saves my file with the names camera0-00001.jpg, camera0-00002.jpg, etc.

  Then I rename my file with camera0-HH-mm-ss-(1-30).jpeg based on the modified time of the file.

  So in the end I have 4 files with the same time and same frame like this :
  camera0-12-00-00-1.jpeg
  camera1-12-00-00-1.jpeg
  camera2-12-00-00-1.jpeg
  camera3-12-00-00-1.jpeg

  My issue is that the file may be offset from one to two frame. They may have the same name but sometime one or two camera may show different frame.

  Is there a way to be sure that the capture frames has the actual time of the capture and not the time of the creation of the file ?