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• FFMPEG - format not available ?

  16 mai 2013, par Julien Greard

  I'm converting some code from FFMPEG 0.8 to FFMPEG 1.2. I have an error during the call to the method avcodec_open2() : "Specified pixel format %s is invalid or not supported". The format I use is : AV_PIX_FMT_RGB24. It should be enabled by default, right ?

  Below is my code :

  av_register_all();
  
  
  
  codec = avcodec_find_encoder(AV_CODEC_ID_MPEG2VIDEO);
  
  
  
  if(!codec)
  
  {
  
      throw SystemException("codec not found");
  
  }
  
  
  
  codecContext = avcodec_alloc_context3(codec);
  
  
  
  codecContext->bit_rate = 200000;
  
  codecContext->time_base.den = 1;
  
  codecContext->time_base.num = 90000;
  
  codecContext->gop_size = 8;
  
  codecContext->pix_fmt = AV_PIX_FMT_RGB24;
  
  
  
  _codecContext->width = 320
  
  _codecContext->height = 240
  
  
  
  if(avcodec_open2(_codecContext, _codec, NULL) < 0)
  
  {
  
      throw SystemException("Unable to open codec");
  
  }

• Encode video of powerpoint presentation for HTML5 playback

  17 avril 2013, par user2291446

  We have a number of powerpoint presentations that have been converted to 16:9
  aspect ratio and then converted into mp4 "master videos" with an "apple TV" 720p
  profile. These powerpoint presentations are voice annotated. So in essence, we
  show a slide and then let the annotation sound play for a while, then go to the
  next slide, and so on. The resulting mp4 master video is somewhere around 900MB
  on average.

  Here is an example of the master video

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input.mp4' :
  Metadata :
      major_brand : isom
      minor_version : 512
      compatible_brands : isomiso2avc1mp41
      creation_time : 1970-01-01 00:00:00
      encoder : Lavf52.104.0
    Duration : 02:00:57.65, start : 0.000000, bitrate : 970 kb/s
      Stream #0:0(und) : Video : h264 (Main) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 836 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc
      Metadata :
        creation_time : 1970-01-01 00:00:00
        handler_name : VideoHandler
      Stream #0:1(und) : Audio : aac (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 127 kb/s
      Metadata :
        creation_time : 1970-01-01 00:00:00
        handler_name : SoundHandler
  

  We are trying to get these presentations to play on the web on as many
  devices/browsers as possible including some that don't do HTML5 (IE7/IE8). We
  have narrowed down our player of choice which is mediaElement and have extracted
  some "cue points" from the powerpoint presentation that mark where the slides
  are changing. We have also captured thumbnails for those cuepoints such that we
  now have a nice list of thumbnails for each slide and an associated cuepoint in
  the video where the particular slide begins.

  Here comes the problem...due to the large size of the master video it is not
  practical for us to use the master video with our mediaElement player. We do
  need to transcode the master video to mp4 and ogv in order to get decent
  device/browser coverage.

  We do not seem to be able to find a suitable transcoding strategy to reduce the
  size of the video. We have played with numerous ffmpeg settings and were able to
  reduce the size but when we do so we compromise the ability to jump to specific
  cue points.

  It works well for browsers that do HTML5 video natively (Chrome and Firefox) but
  not for the flash fallback of mediaElement (IE7/IE8) which uses the mp4 file and
  seemingly is very tied to the number and frequency of key frames in the video in
  order to allow for clean seeking and skipping using the cue points.

  Seeing that we are talking about a video that has only slides (practically 90
  static images per presentation) and some sound we imagine it must be possible to
  transcode as such that the keyframes fall at the cue points or near the
  cuepoints, and that the size of the video could be drastically reduced while
  still allowing for smooth seeking and skipping.

• Merge remote-tracking branch ’qatar/master’

  29 juillet 2013, par Michael Niedermayer

  Merge remote-tracking branch ’qatar/master’
  * qatar/master :
  
    hls : Create an AVProgram for each variant
  Conflicts :
  
  	libavformat/hls.c
  See : 23db5418ed2ebaddbbc57a45b81caa6e94724587
  
  Merged-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavformat/hls.c