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• 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);

• FFprobe path video filter [closed]

  4 avril 2021, par Com Media

  Im trying this

  


  ffprobe -f lavfi -i "movie=E:\video.mp4,blackframe=1" -show_entries frame=pkt_pts_time:frame_tags -print_format json


  


  But always fail with every path... What is wrong ?

  


  [Parsed_movie_0 @ 0000026a24f6e780] Failed to avformat_open_input 'E'
[lavfi @ 0000026a24f6ce00] Error initializing filter 'movie' with args 'E :\video.mp4'
movie=E :\video.mp4,blackframe=1 : No such file or directory

  


• FFMPEG gem is not generate correct bitrate value for a video in rails

  23 juin 2023, par Francis

  I am using FFMPEG gem in rails, and I want to store bitrate value for a video in a table

  


  I put this code in utility library/module

  


  movie = FFMPEG::Movie.new(path)
media_detail = {duration: movie.duration, bitrate: movie.bitrate, resolution: movie.resolution}


  


  On the show page I am using number_to_human_size rails helper method for more understandable representation

  


  number_to_human_size(convert_bit_to_byte(file.bitrate))

def convert_bit_to_byte(bitrate_value)
     (bitrate_value.to_i*125)
end


  


  So I want an average bitrate value for a video in bytes for number_to_human_size method for good representation but I am not getting the average value and FFMPEG gem generates everything as expected but only in bitrate there is some problem.