Recherche avancée

Sur d’autres sites (7247)

• Converting any video to iPhone - transcoding logic/algorithm ?

  28 septembre 2012, par cajwine

  I have many-many video files in different formats (mostly avi). For example, some relevant lines from ffprobe :

    Duration: 02:27:14.70, start: 0.000000, bitrate: 664 kb/s
  
      Stream #0.0: Video: mpeg4, yuv420p, 608x256 [PAR 1:1 DAR 19:8], 23.98 tbr, 23.98 tbn, 23.98 tbc
  
      Stream #0.1: Audio: mp3, 44100 Hz, stereo, s16, 96 kb/s
  
  
  
    Duration: 00:20:51.84, start: 0.000000, bitrate: 3286 kb/s
  
      Stream #0.0: Video: mpeg4, yuv420p, 640x480 [PAR 1:1 DAR 4:3], 25 tbr, 25 tbn, 25 tbc
  
      Stream #0.1: Audio: mp3, 48000 Hz, stereo, s16, 128 kb/s
  
  
  
    Duration: 01:26:01.84, start: 0.000000, bitrate: 845 kb/s
  
      Stream #0.0: Video: mpeg4, yuv420p, 704x544 [PAR 1:1 DAR 22:17], 25 fps, 25 tbr, 25 tbn, 30k tbc
  
      Stream #0.1: Audio: mp3, 44100 Hz, stereo, s16, 128 kb/s
  
  
  
    Duration: 01:42:25.68, start: 0.000000, bitrate: 952 kb/s
  
      Stream #0.0: Video: h264 (High), yuv420p, 600x244 [PAR 1:1 DAR 150:61], 25 fps, 25 tbr, 25 tbn, 50 tbc
  
      Stream #0.1: Audio: mp3, 48000 Hz, stereo, s16, 112 kb/s

  As you can see, the bitrates, video-sizes, codecs are vary. Want write a script (bash, perl) what will convert them for iPhone with ffmpeg.

  With googling i found many different ffmpeg profiles, but all profiles are "static", e.g. converts video to same resolution and this is probably not the right way, because i have many different video resolutions with many different bitrates. (this applies for the audio too).

  I'm able write the script - but need help with one basic question.

  I need help with the algorithm how to calculate the values for ffmpeg arguments from the above ffprobe results. E.g. when have video 704x544 and 845kb/s and another video with smaller size 640x480 but 3200kb/s bitrate - how to calculate the "right values" for ffmpeg in the script ?

  What is right algorithm/logic for transcoding video for the desired device ? (in my case iPhone)

  If someone care, I have ffmpeg recompiled with "nonfree" codecs, and have mencoder (from mplayer package) too.

  Second : In the avi containers are many videos already in the mpeg4 format. How to determine the "fastest" converting profile ? Mean a profile, where ffmpeg will only do the less-possible calculations, so probably will leave as-is : the format mpeg4, the size, the bitrate and "only" will change the container format. Is this possible ?

  I was read many ffmpeg SO questions, but not find answers - maybe I missed something. Can somebody point me to some good documents ?

• FFMPEG and DXVA2

  11 septembre 2017, par Bobnono

  I’ve made a player for IP camera (fullHD H264) with FFMPEG
  I code under windows with Qt.I need the lowest latency as possible and the best result I can get is done whith :

  • I got the packet with live555,
  • decode with ffmpeg
  • display it with SDL.

  But with "slow" CPU I have lot of latency if the bitrate is too high or it can’t handle 1080p.

  I really want to try hardware acceleration with DXVA2 to see if I can get better performance especially in slowest CPU.

  But i really don’t know how to proceed. I have to build FFMPEG with —enable-dxva2 and —enable-hwaccel=h264_dxva2 ? or Zeranoe build
  I have never use Direct X, do I need Direct X knowledge, or ffmpeg with —enable-dxva2 and —enable-hwaccel=h264_dxva2 care of everything ?

  Thank you

  Edit :

  Hello, I use this post to help me in my HW acceleration with FFMPEG
  Failed to execute : 0x80070057, when decoding video via ffmpeg with dxva2

  I decode the packet with

  avcodec_decode_video2(pCodecCtx, pFrame, &gotPic, &packet);

  and I’m getting my decoded frame with

  dxva2_retrieve_data_call(pCodecCtx, pFrame, &gotPic, &packet);

  I tried to convert it

  sws_scale(img_convert_affic, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);

  and copy the buffer to a Qimage

  LastFrame=QImage(w,h,QImage::Format_RGB888);
  
  for(int y=0;ydata[0]+y*pFrameRGB->linesize[0],w*3);

  I got my picture but with lot of artefact and after few seconds I got a segmentation fault in dxva2_retrieve_data_call(pCodecCtx, pFrame, &gotPic, &packet);

  Edit :
  Problem solved i didn’t check if I got a picture before retreiving it.
  But the performance are very poor on my desktop cmputer (intel core i5 650, 4GB RAM, ATI HD5800) it consumes 5% more of CPU, 3 times more RAM, and lot of corrupt frame.
  It’s better on a newer computer, but soft decoder is better.
  dxva2_retrieve_data_call and sws_swale consume lot of time when hwaccel is enabled ...

  Is there a way to display NV12 picture in Qt (no sws_scale conversion) and there is a way to optimise dxva_retrieve_data_call ?

• FFMPEG and DXVA2

  5 février 2016, par Bobnono

  I’ve made a player for IP camera (fullHD H264) with FFMPEG
  I code under windows with Qt.I need the lowest latency as possible and the best result I can get is done whith :

  • I got the packet with live555,
  • decode with ffmpeg
  • display it with SDL.

  But with "slow" CPU I have lot of latency if the bitrate is too high or it can’t handle 1080p.

  I really want to try hardware acceleration with DXVA2 to see if I can get better performance especially in slowest CPU.

  But i really don’t know how to proceed. I have to build FFMPEG with —enable-dxva2 and —enable-hwaccel=h264_dxva2 ? or Zeranoe build
  I have never use Direct X, do I need Direct X knowledge, or ffmpeg with —enable-dxva2 and —enable-hwaccel=h264_dxva2 care of everything ?

  Thank you

  Edit :

  Hello, I use this post to help me in my HW acceleration with FFMPEG
  Failed to execute : 0x80070057, when decoding video via ffmpeg with dxva2

  I decode the packet with

  avcodec_decode_video2(pCodecCtx, pFrame, &gotPic, &packet);

  and I’m getting my decoded frame with

  dxva2_retrieve_data_call(pCodecCtx, pFrame, &gotPic, &packet);

  I tried to convert it

  sws_scale(img_convert_affic, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);

  and copy the buffer to a Qimage

  LastFrame=QImage(w,h,QImage::Format_RGB888);
  
  for(int y=0;ydata[0]+y*pFrameRGB->linesize[0],w*3);

  I got my picture but with lot of artefact and after few seconds I got a segmentation fault in dxva2_retrieve_data_call(pCodecCtx, pFrame, &gotPic, &packet);

  Edit :
  Problem solved i didn’t check if I got a picture before retreiving it.
  But the performance are very poor on my desktop cmputer (intel core i5 650, 4GB RAM, ATI HD5800) it consumes 5% more of CPU, 3 times more RAM, and lot of corrupt frame.
  It’s better on a newer computer, but soft decoder is better.
  dxva2_retrieve_data_call and sws_swale consume lot of time when hwaccel is enabled ...

  Is there a way to display NV12 picture in Qt (no sws_scale conversion) and there is a way to optimise dxva_retrieve_data_call ?