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• ffmpeg streaming on embedded device [closed]

  18 février 2012, par JoeFrizz

  I have a problem with the ffmpeg streaming application.

  When I try to dump a RTSP (mp4) stream to a file on my
  desktop (Ubuntu) everything works fine...

  What I actually want to do is to download the same stream
  with an embedded system (very limited CPU power)...

  While I get about 150 fps on the desktop my embedded system loads
  about 2 fps only and struggles after downloading
  of approx. 150 frames. All the other frames (about 1000 total)
  are dublicated or missing...

  Can this problem be fully explained by the weak CPU power
  of the embedded system ? Does the RTSP protocol allow streaming
  far below the normal rates (my desktop achieves) ?

  Are there any tricks to overcome that issue ?

• Is there a Heroku-supported method for getting the length of an audio file in seconds ?

  12 juillet 2013, par Ben West

  I'm trying to implement

  http://blog.firmhouse.com/validate-length-of-an-audio-file-when-using-paperclip-and-s3

  But I'm unsure what gem provided FFMpegWrapper, and I'd like to use Heroku to deploy my app for testing. Does heroku support something that will work for this ?

  full Rails Application source :

  https://github.com/mrgenixus/sound-byte

  Relevant Model :

  https://github.com/mrgenixus/sound-byte/blob/master/app/models/episode.rb

• probing individual klv streams for specific signature/header

  17 juin 2019, par J Heyman

  Currently, the software I support processes the different streams within a video container (.ts, .mp4, .mpg, etc) without any issues as long as there is only one(1) type of each codec stream.

  I’ve recently encountered a video sample that actually contains three(3) identified AV_CODE_ID_SMPTE_KLV streams. As I loop through the three streams, one of them is the stream I need.
  I haven’t been able to figure out an easy way to do the specific query I need (check for known header bytes in the stream).

      ...
  
      for (i = 0; i < nb_streams; i++) {
  
         int real_stream_index = program ? program[i] : i;
  
         AVStream *st          = ic->streams[real_stream_index];
  
         AVCodecParameters *par = st->codecpar;
  
         if (par->codec_type != type)
  
            continue;
  
         if (id != AV_CODEC_ID_NONE) {
  
            if (par->codec_id != id)
  
               continue;
  
         }
  
         if (wanted_stream_nb >= 0 && real_stream_index != wanted_stream_nb)
  
            continue;
  
         if (type == AVMEDIA_TYPE_AUDIO && !(par->channels && par->sample_rate))
  
            continue;
  
         disposition = !(st->disposition & (AV_DISPOSITION_HEARING_IMPAIRED | AV_DISPOSITION_VISUAL_IMPAIRED));
  
         count = st->codec_info_nb_frames;
  
         bitrate = par->bit_rate;
  
         multiframe = FFMIN(5, count);
  
         if ((best_disposition >  disposition) ||
  
             (best_disposition == disposition && best_multiframe >  multiframe) ||
  
             (best_disposition == disposition && best_multiframe == multiframe && best_bitrate >  bitrate) ||
  
             (best_disposition == disposition && best_multiframe == multiframe && best_bitrate == bitrate && best_count >= count))
  
            continue;
  
         best_disposition = disposition;
  
         best_count   = count;
  
         best_bitrate = bitrate;
  
         best_multiframe = multiframe;
  
         ret          = real_stream_index;

  My thought was to add another || to the complex if{} above, but I haven’t been able to figure out how to do the comparison I need (looking for the header bytes).

  I’ve looked into existing documentation, and thought that accessing the probe_data structure within the AVStream contained within the AVFormatContext structure would give me the first few bytes of the stream. No such luck, as the probe_data structure is empty even though we’ve done a probe on the file itself.

  fprintf(stderr, "Filename: %s\t buf_size: %d\n", st-> probe_data.filename, st-> probe_data.buf_size);