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• Getting Flask to accept chunked encoding

  22 août 2014, par Andrew

  Is it possible to have Python Flask reading chunked encoding sent to it ?

  I have a very simple routine where I want to read the output from ffmpeg -progress which sends progress updates via chunked encoding.

  What happens though is Flask closes the connection after the first POST.

  my routine is very simple

  @app.route('/status', methods=['POST','GET'])
  
  def get_status():
  
      logging.error(request.headers)
  
      logging.error(request.data)
  
      logging.error(request.args)
  
      return "OK"

  What I see in the output is as follows and ffmpeg closes when the POST does

  ERROR:root:Transfer-Encoding: chunked
  
  Content-Length:
  
  User-Agent: Lavf/55.45.100
  
  Connection: close
  
  Host: localhost:50000
  
  Accept: */*
  
  Content-Type:
  
  
  
  
  
  ERROR:root:
  
  ERROR:root:ImmutableMultiDict([])

  Excuse my lazy logging to error. Note in this case I am running Flask in debug mode but otherwise would like to run in Tornado or an equivalent simple container with permissions that make it easy to run command line programs like ffmpeg

• Mencoder - Audio is longer than Video Stream

  30 juillet 2014, par Jasper

  I am trying use some images and audio to create video using mencoder.
  But my audio file could be much longer.

  Example:
  
  5 images. 
  
  fps: 1
  
  desired video length: 5 seconds
  
  audio file length is: 20 seconds.
  
  
  
  mencoder mf://*.jpg -mf fps:1.0 -oac mp3lame -audiofile myaudio.mp3 -ovc lavc vcodec=mpeg4 -o myvideo.mpeg

  This produces a video that is :
  20 seconds long (as long as audio file length).
  The image slide show ends at 5 seconds, after that there is only audio playing (from 6th to 20th second).

  How can i make mencoder to generate video of only duration where video stream exists. In this case end the video at 5 seconds.

  ffmpeg has a -shortest option for exactly this kind of use case. But i cannot find equivalent of that in mencoder.

• How can I use libav to encode video to dvd compliant mpeg2

  18 juillet 2014, par Dave Camp

  Im new to using FFMpeg and I’d like to do the equivalent of using the command line option -f dvd but in my app, by using the libav api. In the source of FFMpeg the option sets up some parameters as

   opt_video_codec(o, "c:v", "mpeg2video");
  
   opt_audio_codec(o, "c:a", "ac3");
  
   parse_option(o, "f", "dvd", options);
  
  
  
   parse_option(o, "s", norm == PAL ? "720x576" : "720x480", options);
  
   parse_option(o, "r", frame_rates[norm], options);
  
   parse_option(o, "pix_fmt", "yuv420p", options);
  
   av_dict_set(&o->g->codec_opts, "g", norm == PAL ? "15" : "18", AV_DICT_DONT_OVERWRITE);
  
  
  
   av_dict_set(&o->g->codec_opts, "b:v", "6000000", AV_DICT_DONT_OVERWRITE);
  
   av_dict_set(&o->g->codec_opts, "maxrate", "9000000", AV_DICT_DONT_OVERWRITE);
  
   av_dict_set(&o->g->codec_opts, "minrate", "0", AV_DICT_DONT_OVERWRITE); // 1500000;
  
   av_dict_set(&o->g->codec_opts, "bufsize", "1835008", AV_DICT_DONT_OVERWRITE); // 224*1024*8;
  
  
  
   av_dict_set(&o->g->format_opts, "packetsize", "2048", AV_DICT_DONT_OVERWRITE);  // from www.mpucoder.com: DVD sectors contain 2048 bytes of data, this is also the size of one pack.
  
   av_dict_set(&o->g->format_opts, "muxrate", "10080000", AV_DICT_DONT_OVERWRITE); // from mplex project: data_rate = 1260000. mux_rate = data_rate * 8
  
  
  
   av_dict_set(&o->g->codec_opts, "b:a", "448000", AV_DICT_DONT_OVERWRITE);
  
   parse_option(o, "ar", "48000", options);

  How do these relate to the libav api ?

  The incoming video frames are at the correct resolution for pal of 720x576 in yuv420p format. Some of my params...

  pCodec = avcodec_find_encoder(AV_CODEC_ID_MPEG2VIDEO);
  
  
  
  pContext->bitrate = 48000000;
  
  pContext->width = 720;
  
  pContext->height = 576;
  
  
  
  AVRational fps = {1,25};
  
  pContext->time_base = fps;
  
  
  
  pContext->gop_size = 15;
  
  pContext->max_b_frmaes = 2;
  
  pContext->pix_fmt = AV_PIX_FMT_YUV420P;
  
  
  
  av_set_dict(&pDict,"packet_size","2048",0); // This seems to be ignored?
  
  
  
  avcodec_open2(pContext,pCodec,&pDict);

  The AVDictionary... What is the dictionary ? How does it relate the encoding process ? Is it simply a user dictionary for passing a collection of settings around your code ?

  Ultimately I’d like to be able to transcode incoming video frames that are already in the correct size and format for pal dvd and output a dvd compliant mpeg2 video ( data packets of 2048 bytes ). I understand the mpeg2 video format but I’m confused with ffmpeg params.

  Thanks !