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• 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 ?

• how to crop and overlay dshow ?

  19 novembre 2022, par Yac Ine

  hello I have a problem with ffmpeg I can't resize my web cam which is 1080p I would like some help pleaseffmpeg -y -rtbufsize 100M  -thread_queue_size 9400  -f dshow  -i video="USB Live Camera":audio="Microphone (2- Trust GXT 232 Microphone)"  -thread_queue_size 9400  -f gdigrab -draw_mouse 0  -i desktop -b:v 10M -c:v libx264 -c:a aac -filter_complex "[1:v]pad=height=ih+10:color=black[b]; [b][0:v]overlay=(main_w-overlay_w):main_h-overlay_h[v] -video_size 200x200"  -map "[v]" -map 0:a -c:a aac -r 20 -preset ultrafast -tune zerolatency -c:v libx264 -c:a aac -crf 30 -pix_fmt yuv420p -fflags nobuffer -f flv rtmp://localhost/hls/stream6

  


  here is my command line

  


• Can I double a video duration by halving the FPS using FFMPEG ?

  14 août 2017, par synner

  I shot a time-lapse with my DSLR which the camera auto-assembled into a 10 sec MOV file - 1080p, 60 fps (600 frames total). What I am trying to do is double the duration (from 10 to 20 seconds) by halving the FPS rate (from 60 fps to 30 fps).

  I tried various links here on SO and on the Interwebz but none seem to do the trick. Almost all propositions on the webz refer to using the -filter:v "setpts=2*PTS" option with or without the -r parameter, but all I end up is 10-sec MOV/MP4/MVK with 30 FPS (50% of frames are dropped).

  Exact commands I’ve used :

  ffmpeg.exe -y -i ..\..\DSC_0898.MOV -c:v libx264 -preset veryslow -r 30 -crf 18 -movflags faststart -filter:v "setpts=2*PTS" -vf deshake -vf "eq=contrast=1.3:brightness=-0.05:saturation=1.3" ..\..\output.mkv -hide_banner -an
  
  
  
  ffmpeg.exe -y -i ..\..\DSC_0898.MOV -c:v libx264 -preset veryslow -r 30 -crf 18 -movflags faststart -filter:v "setpts=2*PTS" -vf deshake -vf "eq=saturation=1.2" ..\..\output.mkv -hide_banner -an
  
  
  
  ffmpeg.exe -y -i ..\..\DSC_0898.MOV -movflags faststart -r 30 -filter:v "setpts=2*PTS" -vf deshake -vf "eq=saturation=1.2" ..\..\output.mp4 -hide_banner -an