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• Probe function in ffmpeg

  14 octobre 2014, par eejs

  I am trying to write a demuxer for STL subtitle format(FFmpeg). I am having trouble understanding how the probe function is referenced in ffmpeg.
  I have the following code for my probe :

  #include "avformat.h"
  
  #include "internal.h"
  
  #include "subtitles.h"
  
  #include "libavutil/intreadwrite.h"
  
  
  
  typedef struct {
  
      FFDemuxSubtitlesQueue q;
  
  } STLContext;
  
  
  
  static int stl_probe(AVProbeData *p)
  
  {
  
      char c;
  
      const unsigned char *ptr = p->buf;
  
      av_log(0,100,"printing the probe function");
  
      while(*ptr=='\r' || *ptr=='\n' || *ptr=='$' || (ptr[0]=='/' && ptr[1]=='/'))
  
          ptr+=ff_subtitles_next_line(ptr);
  
      if (sscanf(ptr, "%*d:%*d:%*d:%*d , %*d:%*d:%*d:%*d , %c", &c) == 1)
  
          return AVPROBE_SCORE_MAX;
  
       return 0;
  
  
  
  }
  
  static int64_t get_pts(char **buf, int *duration)
  
  {
  
          int hh1, mm1, ss1, ms1;
  
          int hh2, mm2, ss2, ms2;
  
          int len=0;
  
          if (sscanf(*buf, "%2d:%2d:%2d:%2d , %2d:%2d:%2d:%2d , %n",
  
                     &hh1, &mm1, &ss1, &ms1,
  
                     &hh2, &mm2, &ss2, &ms2, &len) >= 8 && len>0) {
  
              int64_t start = (hh1*3600LL + mm1*60LL + ss1) * 100LL + ms1;
  
              int64_t end   = (hh2*3600LL + mm2*60LL + ss2) * 100LL + ms2;
  
              *duration = end - start;
  
              *buf+=len;
  
              return start;
  
           }
  
          return AV_NOPTS_VALUE;
  
  }
  
  
  
  static int stl_read_header(AVFormatContext *s)
  
  {
  
      STLContext *stl = s->priv_data;
  
      AVStream *st = avformat_new_stream(s, NULL);
  
  
  
      if (!st)
  
          return AVERROR(ENOMEM);
  
      avpriv_set_pts_info(st, 64, 1, 100);
  
      st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;
  
      st->codec->codec_id   = AV_CODEC_ID_TEXT;
  
  
  
      while (!avio_feof(s->pb)) {
  
          char line[4096];
  
          char *p = line;
  
          const int64_t pos = avio_tell(s->pb);
  
          int len = ff_get_line(s->pb, line, sizeof(line));
  
          int64_t pts_start;
  
          int duration;
  
          if (!len)
  
              break;
  
  
  
          line[strcspn(line, "\r\n")] = 0;
  
  
  
          pts_start = get_pts(&p , &duration);
  
          if (pts_start != AV_NOPTS_VALUE) {
  
              AVPacket *sub;
  
  
  
              sub = ff_subtitles_queue_insert(&stl->q, p, strlen(p), 0);
  
              if (!sub)
  
                  return AVERROR(ENOMEM);
  
              sub->pos = pos;
  
              sub->pts = pts_start;
  
              sub->duration = duration;
  
          }
  
      }
  
  
  
      ff_subtitles_queue_finalize(&stl->q);
  
      return 0;
  
  
  
  }
  
  static int stl_read_packet(AVFormatContext *s, AVPacket *pkt)
  
  {
  
      STLContext *stl = s->priv_data;
  
      return ff_subtitles_queue_read_packet(&stl->q, pkt);
  
  }
  
  
  
  static int stl_read_seek(AVFormatContext *s, int stream_index,
  
                               int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
  
  {
  
      STLContext *stl = s->priv_data;
  
      return ff_subtitles_queue_seek(&stl->q, s, stream_index,
  
                                     min_ts, ts, max_ts, flags);
  
  }
  
  
  
  static int stl_read_close(AVFormatContext *s)
  
  {
  
      STLContext *stl = s->priv_data;
  
      ff_subtitles_queue_clean(&stl->q);
  
      return 0;
  
  }
  
  
  
  AVInputFormat ff_stl_demuxer = {
  
      .name           = "stl",
  
      .long_name      = NULL_IF_CONFIG_SMALL("STL subtitles"),
  
      .priv_data_size = sizeof(STLContext),
  
      .read_probe     = stl_probe,
  
      .read_header    = stl_read_header,
  
      .read_packet    = stl_read_packet,
  
      .read_seek2     = stl_read_seek,
  
      .read_close     = stl_read_close,
  
      .extensions     = "stl",
  
  };

  Output of ./ffmpeg -f stl -i Test.stl Test.srt

  ffmpeg version N-66838-g9071bab Copyright (c) 2000-2014 the FFmpeg developers
  
    built on Oct 14 2014 12:28:54 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
  
    configuration: 
  
    libavutil      54. 10.100 / 54. 10.100
  
    libavcodec     56.  4.101 / 56.  4.101
  
    libavformat    56.  9.100 / 56.  9.100
  
    libavdevice    56.  1.100 / 56.  1.100
  
    libavfilter     5.  1.105 /  5.  1.105
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  1.100 /  1.  1.100
  
  Input #0, stl, from '/home/eejya/SubtitleTesting/UK_FINAL_240511.stl':
  
    Duration: N/A, bitrate: N/A
  
      Stream #0:0: Subtitle: text
  
  Output #0, srt, to '/home/eejya/SubtitleTesting/UkTest.srt':
  
    Metadata:
  
      encoder         : Lavf56.9.100
  
      Stream #0:0: Subtitle: subrip (srt)
  
      Metadata:
  
        encoder         : Lavc56.4.101 srt
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (text (native) -> subrip (srt))
  
  Press [q] to stop, [?] for help
  
  size=      10kB time=00:27:10.06 bitrate=   0.0kbits/s    
  
  video:0kB audio:0kB subtitle:4kB other streams:0kB global headers:0kB muxing overhead: 121.594238%

  when I run the command

  ./ffmpeg -i Test.stl Test.srt 

  I don’t see any output printed by av_log and it says that the probe score is very less which may lead to mis-detection. That would mean only the extension is being checked.So, either my probe function is not being called or the buffer isn’t being read.
  How do I check whether my probe function is being called or not ?
  Also does the low score warning imply that the function is being called ?

• Converting DAV to MP4 and OGG

  27 mars 2015, par mackowiakp

  I want to prepare WEB page containing films from security camera recorders. Each recorder transmit video files in DAV format so each film is converted to MP4 format by script, using such syntax :

  ffmpeg -y -i movie.dav -vcodec libx264 -crf 24 movie.mp4

  So I included in HTMLv5 code such entry :

   <video width="320" height="240">
  
    <source src="movie.mp4" type="video/mp4">
  
  </source></video> 

  It works correctly with Chrome but not with Firefox. For proper work in FF it is necessary add link to OGG file. So correct HTMLv5 syntax for both browsers should look like this :

   <video width="320" height="240">
  
    <source src="movie.mp4" type="video/mp4">
  
    <source src="movie.ogg" type="video/ogg">
  
  </source></source></video>

  Can anybody help me to pass correct ffmpeg syntax to create OGG file ?

  Output from console after using -movflags +faststart options

  [maciek@piotr MMM]$ ../ffmpeg-2.4.2-64bit-static/ffmpeg -movflags +faststart -y -i   04.24.23-04.24.38\[M\]\[@0\]\[0\].dav -vcodec libx264 -crf 24 10.mp4
  
  ffmpeg version 2.4.2-   http://johnvansickle.com/ffmpeg/    Copyright (c) 2000-2014 the FFmpeg developers
  
    built on Oct  9 2014 07:24:56 with gcc 4.8 (Debian 4.8.3-11)
  
    configuration: --enable-gpl --enable-version3 --disable-shared --disable-debug --enable-runtime-cpudetect --enable-libmp3lame --enable-libx264 --enable-libx265 --enable- libwebp --enable-libspeex --enable-libvorbis --enable-libvpx --enable-libfreetype --enable-fontconfig --enable-libxvid --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-gray --enable-libopenjpeg --enable-libopus --disable-ffserver --enable-libass --enable-gnutls --cc=gcc-4.8
  
    libavutil      54.  7.100 / 54.  7.100
  
    libavcodec     56.  1.100 / 56.  1.100
  
    libavformat    56.  4.101 / 56.  4.101
  
    libavdevice    56.  0.100 / 56.  0.100
  
    libavfilter     5.  1.100 /  5.  1.100
  
    libswscale      3.  0.100 /  3.  0.100
  
    libswresample   1.  1.100 /  1.  1.100
  
    libpostproc    53.  0.100 / 53.  0.100
  
  Option movflags not found.

• Ffmpeg, avconv and sameq

  25 avril 2015, par xiaose

  Earlier I wrote so :

  ffmpeg -i input.mp4 -sameq output.mp3

  ...and thus receive audio from video file. Ffmpeg just taken out or converted audio to mp3 with an appropriate quality. All thanks to key : -sameq [use same quantizer as source]

  Now in Ubuntu instead of ffmpeg we have libav and there (in man for avcomv) I see no -sameq key. Well, here is a question : what I have to do now ?..

  What I have to do now to get converted audio file with the same quality as in original ?

  PS. -sameq : Use same quantizer as source (implies VBR).

  $ man ffmpeg | col -b > ./man_ffmpeg

  this man_ffmpeg is there : http://pastebin.com/qYxz1M1E

  FFMPEG(1)
  
  NAME
  
     ffmpeg - ffmpeg video converter
  
  SYNOPSIS
  
     ffmpeg [[infile options][-i infile]]... {[outfile options] outfile}...
  
  ...
  
  ...
  
  ...
  
  -sameq
  
     Use same quantizer as source (implies VBR).
  
  ...
  
  ...
  
  ...
  
  SEE ALSO
  
     avplay(1), avprobe(1), avserver(1) and the Libav HTML documentation
  
  AUTHORS
  
     The Libav developers
  
  2014-02-06
  
  FFMPEG(1)