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• ffmpeg + glfwGetTime()

  3 septembre 2013, par Javier Ramírez

  I try to control the playback speed of my video using ffmpeg + opengl. But I have problems.

  My video is encoded at 25 fps and plays very fast. I added this in my code.

  tiempo = glfwGetTime();
  
  duracion = 1.0/25.0; // 1 second / 25 fps
  
  
  
  while(1){
  
  
  
  ...        
  
  
  
    if(glfwGetTime() > tiempo + duracion){
  
      if(av_read_frame(pFormatCtx,&packet) >= 0){
  
        if(packet.stream_index == 0){
  
          avcodec_decode_video2(pCodecCtx,pFrame,&frameFin,&packet);
  
          if(frameFin)sws_scale(img_convert_ctx,pFrame->data,pFrame->linesize,0,pCodecCtx->height,pFrameRGB->data,pFrameRGB->linesize);
  
        }
  
        av_free_packet(&packet);
  
      }
  
      tiempo = glfwGetTime();
  
    }
  
  
  
  ...
  
  
  
  }

  The problem is that now the video plays slower than it should. What is the problem ?

• Realtime http ogg stream with ffmpeg latency

  4 septembre 2013, par MastErAldo

  I'm using the Kinect as an infrared camera and through a named pipe i send each captured frame to FFMPEG which encodes them in an ogg/theora stream that is sent to an http server.
  The server than broadcasts the video to every connected user. The users use the Cortado applet to play the video.

  The video plays fine, but the latency keeps on increasing continuously. So if at the beginning the latency is about 100ms, in a minute it reaches up to 10 seconds.

  However the playback is smooth, the bandwidth is enough and the encoding machine and the server CPU is not overloaded, so I don't understand what can make the latency increase.

  This is the ffmpeg command line that we use :

  ffmpeg.exe -f segment -f rawvideo -pix_fmt rgb565 -s 640x480 -i \\.\pipe\CAH_STREAM_PIPE -fflags nobuffer -r 60 -b:v 128k -bufsize 1024k -s 240x160 -codec:v libtheora -qscale:v 1 -f ogg http://localhost/video_stream.ogg

  Am I missing some parameters or setting some of them to wrong values ? Or the problem is elsewhere ?

  BTW : I'm not sure about using nobuffer and bufsize at the same time

  Thanks

• mencoder generate mp4 h.264 from jpg playback stops in html videotag chrome

  10 septembre 2013, par jedimorten

  So I have some images from which I create a video with mencoder.

  mencoder -idx -nosound -noskip -of lavf -lavfopts format=mp4 -ovc x264 -x264encopts pass=1:bitrate=2000:crf=24 -o output.mp4 -mf fps=15 'mf://@files.txt'

  (where files.txt is a list of all the files sorted in the right order)

  The videos is created without problems, it plays fine in desktop-player like vlc, but in chrome (on mac) and chromium (ubuntu) some of the videoes has "breakpoints" in which the video just stops.

  Take a look at this fiddle.

  I made an ugly hack (see fiddle) to force a continued play even if the video is damaged, but this does not look very nice when the video has a lot of them "breakpoints".

  For several reasons I need to be using html, so flash would only be a last last resort.
  Any views on what may be causing these breakpoints ? Or a nicer ugly hack to force contiuned playback ?