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• how to explicitly specify matroska format file to be VFR

  19 janvier 2012, par Ulterior

  I am moving my code performing AVI recording with ffmpeg library to matroska format due to native support of VFR stated by format. Changing guess_format to matroska not touching any other settings produced an mkv file which seems to be ok. But the MediaInfo reports it to be CFS (30).

  How do I explicitly state that its VFR ?

  Format                           : Matroska
  
  File size                        : 5.27 MiB
  
  Duration                         : 8s 0ms
  
  Overall bit rate                 : 5 528 Kbps
  
  Writing application              : Lavf52.78.1
  
  Writing library                  : Lavf52.78.1
  
  
  
  Video
  
  ID                               : 1
  
  Format                           : MPEG-4 Visual
  
  Format profile                   : Simple@L1
  
  Format settings, BVOP            : Yes
  
  Format settings, QPel            : No
  
  Format settings, GMC             : No warppoints
  
  Format settings, Matrix          : Default (H.263)
  
  Codec ID                         : V_MPEG4/ISO/ASP
  
  Codec ID/Info                    : Advanced Simple Profile
  
  Duration                         : 8s 0ms
  
  Width                            : 1 280 pixels
  
  Height                           : 720 pixels
  
  Display aspect ratio             : 16:9
  
  Frame rate                       : 30.000 fps
  
  Color space                      : YUV
  
  Bit depth                        : 8 bits
  
  Scan type                        : Progressive
  
  Writing library                  : Intel(R) MPEG-4 encoder based on Intel(R) IPP 6.1 build 137.36[6.1.137.779]
  
  Language                         : English
  
  
  
  Audio
  
  ID                               : 2
  
  Format                           : MPEG Audio
  
  Codec ID                         : A_MPEG/L3
  
  Codec ID/Hint                    : MP3
  
  Duration                         : 8s 0ms
  
  Channel(s)                       : 2 channels
  
  Sampling rate                    : 44.1 KHz
  
  Language                         : English

• Learn Multimedia Programming By Writing A JPEG Decoder

  6 janvier 2011, par Multimedia Mike — Programming

  For those of you who hack on multimedia tech, how did you get started ? Did you begin by studying the mathematical underpinnings of multimedia codec algorithms ? Or did you find a practical problem and jump right in by writing code ? (Personally, I was always more of a nuts & bolts hacker than a math guy.) I ask because I occasionally get emails from aspiring multimedia hackers who want to know where to begin. Invariably, they want to go the math-first route. I heavily discourage this approach.

  I have a crazy idea for anyone who wants a crash course on multimedia hacking : write a JPEG decoder. In doing so, you will be exposed to a lot of key domain concepts such as bitstream parsing, Huffman decoding, dequantization, zigzagging, the dreaded (inverse) discrete cosine transform, YUV vs. RGB colorspaces, macroblock organization, delta coding, and run length coding.

  Sure, JPEG decoding is a solved problem. But that’s hardly the point. Why would you enter an unfamiliar field and hope to come up to speed on the basics by leaping straight into the domain’s unsolved problems ? If you are successful in this exercise, no one will ever use the fruits of your labor, but that doesn’t really matter.

  So, do you want to learn multimedia hacking quickly ? Then grab a JPEG file (maybe create a few contrived ones that are small, have friendly dimensions, and feature predictable patterns), grab a good JPEG reference, and implement the decoding algorithm in the language and platform of your choice.

  On the matter of the reference, my personal favorite reference has always been A note about the JPEG decoding algorithm by Cristi Cuturicu. The English grammar is a bit dodgy but overall, it might be the best reference you’ll find on the matter— as simple as it needs to be, but no simpler.

  Good luck !

• Program hangs while using ffprobe on file with teletext subtitles

  6 août 2012, par Jon

  Having a problem running ffprobe on an MKV file that contains teletext subtitles. Code is in a C# library and works fine for other MKV files.

  Running the latest :

  ffprobe -v
  
  
  
  ffprobe version N-42347-g299387e Copyright (c) 2007-2012 the FFmpeg developers
  
    built on Jul  8 2012 15:44:54 with gcc 4.7.1

  Code :

  string args = string.Format("-show_format -show_streams \"{0}\"", FileName);
  
  
  
  Process p = new Process();
  
  p.StartInfo = new ProcessStartInfo(FFPROBE_PATH);
  
  p.StartInfo.Arguments = args;
  
  p.StartInfo.CreateNoWindow = true;
  
  p.StartInfo.RedirectStandardOutput = true;
  
  p.StartInfo.RedirectStandardError = true;
  
  p.StartInfo.UseShellExecute = false;
  
  p.StartInfo.WorkingDirectory = System.IO.Directory.GetCurrentDirectory();
  
  p.Start();
  
  
  
  while (!p.HasExited)
  
  {
  
      System.Threading.Thread.Sleep(100);
  
  }
  
  
  
  string output = p.StandardOutput.ReadToEnd().Replace("\r\n", "\n");

  The filename has a UNC path - tried using the FileName parameter but got an error, hence passing the filename via the arguments.

  If I run the following commandline :

  ffprobe -show_format -show_streams "\192.168.10.1\content\Breakfast At Tiffany's sample preview.mkv"

  I get the following output (note the errors - "Unsupported codec with id ...") :

  ffprobe -show_format -show_streams "\\192.168.10.1\content\Breakfast At Tiffany's sample preview.mkv"
  
  
  
  ffprobe version N-42347-g299387e Copyright (c) 2007-2012 the FFmpeg developers
  
    built on Jul  8 2012 15:44:54 with gcc 4.7.1
  
    configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-runtime-cpudetect --enable-avisynth --enable-bzlib --enable-fr
  
  ei0r --enable-libass --enable-libcelt --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libfreetype --enable-libgsm --enable-li
  
  bmp3lame --enable-libnut --enable-libopenjpeg --enable-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libutv
  
  ideo --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-libxvid --e
  
  nable-zlib
  
    libavutil      51. 64.100 / 51. 64.100
  
    libavcodec     54. 33.100 / 54. 33.100
  
    libavformat    54. 15.102 / 54. 15.102
  
    libavdevice    54.  1.100 / 54.  1.100
  
    libavfilter     3.  1.100 /  3.  1.100
  
    libswscale      2.  1.100 /  2.  1.100
  
    libswresample   0. 15.100 /  0. 15.100
  
    libpostproc    52.  0.100 / 52.  0.100
  
  Input #0, matroska,webm, from 'c:\dev\content\Breakfast At Tiffany's sample preview.mkv':
  
    Metadata:
  
      creation_time   : 2011-12-14 21:27:01
  
    Duration: 00:01:02.77, start: 0.000000, bitrate: 4071 kb/s
  
      Stream #0:0: Video: h264 (High), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default)
  
      Metadata:
  
        title           : x264   1920x1080   Bitrate=4776 kbps   AvQuant=21.406   Rip by ShivaShanti
  
      Stream #0:1(eng): Audio: ac3, 48000 Hz, 5.1(side), s16, 448 kb/s (default)
  
      Metadata:
  
        title           : English Ac3 5.1 chnls 448 kbps
  
      Stream #0:2(ita): Audio: ac3, 48000 Hz, stereo, s16, 224 kb/s
  
      Metadata:
  
        title           : Italian Ac3 2.0 chnls 224  kbps
  
      Stream #0:3(eng): Subtitle: text (default)
  
      Metadata:
  
        title           : english
  
      Stream #0:4(ita): Subtitle: text
  
      Metadata:
  
        title           : italian
  
      Stream #0:5(dan): Subtitle: text
  
      Metadata:
  
        title           : danish
  
      Stream #0:6(dut): Subtitle: text
  
      Metadata:
  
        title           : dutch
  
      Stream #0:7(fin): Subtitle: text
  
      Metadata:
  
        title           : finnish
  
      Stream #0:8(fre): Subtitle: text
  
      Metadata:
  
        title           : french
  
      Stream #0:9(ger): Subtitle: text
  
      Metadata:
  
        title           : german
  
      Stream #0:10(nor): Subtitle: text
  
      Metadata:
  
        title           : norwegian
  
      Stream #0:11(spa): Subtitle: text
  
      Metadata:
  
        title           : spanish
  
      Stream #0:12(swe): Subtitle: text
  
      Metadata:
  
        title           : swedish
  
      Stream #0:13(eng): Subtitle: text
  
      Metadata:
  
        title           : english hearig impaired
  
  Unsupported codec with id 94210 for input stream 3
  
  Unsupported codec with id 94210 for input stream 4
  
  Unsupported codec with id 94210 for input stream 5
  
  Unsupported codec with id 94210 for input stream 6
  
  Unsupported codec with id 94210 for input stream 7
  
  Unsupported codec with id 94210 for input stream 8
  
  Unsupported codec with id 94210 for input stream 9
  
  Unsupported codec with id 94210 for input stream 10
  
  Unsupported codec with id 94210 for input stream 11
  
  Unsupported codec with id 94210 for input stream 12
  
  Unsupported codec with id 94210 for input stream 13
  
  [STREAM]
  
  index=0
  
  codec_name=h264
  
  codec_long_name=H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
  
  profile=High
  
  codec_type=video
  
  codec_time_base=1001/48000
  
  codec_tag_string=[0][0][0][0]
  
  codec_tag=0x0000
  
  width=1920
  
  height=1080
  
  has_b_frames=2
  
  sample_aspect_ratio=1:1
  
  display_aspect_ratio=16:9
  
  pix_fmt=yuv420p
  
  level=41
  
  timecode=N/A
  
  is_avc=1
  
  nal_length_size=4
  
  id=N/A
  
  r_frame_rate=24000/1001
  
  avg_frame_rate=24000/1001
  
  time_base=1/1000
  
  start_time=0.000000
  
  duration=N/A
  
  bit_rate=N/A
  
  nb_frames=N/A
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  TAG:title=x264   1920x1080   Bitrate=4776 kbps   AvQuant=21.406   Rip by ShivaShanti
  
  [/STREAM]
  
  [STREAM]
  
  index=1
  
  codec_name=ac3
  
  codec_long_name=ATSC A/52A (AC-3)
  
  profile=unknown
  
  codec_type=audio
  
  codec_time_base=1/48000
  
  codec_tag_string=[0][0][0][0]
  
  codec_tag=0x0000
  
  sample_fmt=s16
  
  sample_rate=48000
  
  channels=6
  
  bits_per_sample=0
  
  dmix_mode=-1
  
  ltrt_cmixlev=-1.000000
  
  ltrt_surmixlev=-1.000000
  
  loro_cmixlev=-1.000000
  
  loro_surmixlev=-1.000000
  
  id=N/A
  
  r_frame_rate=0/0
  
  avg_frame_rate=0/0
  
  time_base=1/1000
  
  start_time=0.000000
  
  duration=N/A
  
  bit_rate=448000
  
  nb_frames=N/A
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  TAG:language=eng
  
  TAG:title=English Ac3 5.1 chnls 448 kbps
  
  [/STREAM]
  
  [STREAM]
  
  index=2
  
  codec_name=ac3
  
  codec_long_name=ATSC A/52A (AC-3)
  
  profile=unknown
  
  codec_type=audio
  
  codec_time_base=1/48000
  
  codec_tag_string=[0][0][0][0]
  
  codec_tag=0x0000
  
  sample_fmt=s16
  
  sample_rate=48000
  
  channels=2
  
  bits_per_sample=0
  
  dmix_mode=-1
  
  ltrt_cmixlev=-1.000000
  
  ltrt_surmixlev=-1.000000
  
  loro_cmixlev=-1.000000
  
  loro_surmixlev=-1.000000
  
  id=N/A
  
  r_frame_rate=0/0
  
  avg_frame_rate=0/0
  
  time_base=1/1000
  
  start_time=0.000000
  
  duration=N/A
  
  bit_rate=224000
  
  nb_frames=N/A
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  TAG:language=ita
  
  TAG:title=Italian Ac3 2.0 chnls 224  kbps
  
  [/STREAM]
  
  [STREAM]
  
  index=3
  
  codec_name=unknown
  
  codec_long_name=unknown
  
  profile=unknown
  
  codec_type=subtitle
  
  codec_time_base=1/1000
  
  codec_tag_string=[0][0][0][0]
  
  codec_tag=0x0000
  
  id=N/A
  
  r_frame_rate=0/0
  
  avg_frame_rate=0/0
  
  time_base=1/1000
  
  start_time=0.000000
  
  duration=N/A
  
  bit_rate=N/A
  
  nb_frames=N/A
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  TAG:language=eng
  
  TAG:title=english
  
  [/STREAM]
  
  [STREAM]
  
  index=4
  
  codec_name=unknown
  
  codec_long_name=unknown
  
  profile=unknown
  
  codec_type=subtitle
  
  codec_time_base=1/1000
  
  codec_tag_string=[0][0][0][0]
  
  codec_tag=0x0000
  
  id=N/A
  
  r_frame_rate=0/0
  
  avg_frame_rate=0/0
  
  time_base=1/1000
  
  start_time=0.000000
  
  duration=N/A
  
  bit_rate=N/A
  
  nb_frames=N/A
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  TAG:language=ita
  
  TAG:title=italian
  
  [/STREAM]
  
  [STREAM]
  
  index=5
  
  codec_name=unknown
  
  codec_long_name=unknown
  
  profile=unknown
  
  codec_type=subtitle
  
  codec_time_base=1/1000
  
  codec_tag_string=[0][0][0][0]
  
  codec_tag=0x0000
  
  id=N/A
  
  r_frame_rate=0/0
  
  avg_frame_rate=0/0
  
  time_base=1/1000
  
  start_time=0.000000
  
  duration=N/A
  
  bit_rate=N/A
  
  nb_frames=N/A
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  TAG:language=dan
  
  TAG:title=danish
  
  [/STREAM]
  
  [STREAM]
  
  index=6
  
  codec_name=unknown
  
  codec_long_name=unknown
  
  profile=unknown
  
  codec_type=subtitle
  
  codec_time_base=1/1000
  
  codec_tag_string=[0][0][0][0]
  
  codec_tag=0x0000
  
  id=N/A
  
  r_frame_rate=0/0
  
  avg_frame_rate=0/0
  
  time_base=1/1000
  
  start_time=0.000000
  
  duration=N/A
  
  bit_rate=N/A
  
  nb_frames=N/A
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  TAG:language=dut
  
  TAG:title=dutch
  
  [/STREAM]
  
  [STREAM]
  
  index=7
  
  codec_name=unknown
  
  codec_long_name=unknown
  
  profile=unknown
  
  codec_type=subtitle
  
  codec_time_base=1/1000
  
  codec_tag_string=[0][0][0][0]
  
  codec_tag=0x0000
  
  id=N/A
  
  r_frame_rate=0/0
  
  avg_frame_rate=0/0
  
  time_base=1/1000
  
  start_time=0.000000
  
  duration=N/A
  
  bit_rate=N/A
  
  nb_frames=N/A
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  TAG:language=fin
  
  TAG:title=finnish
  
  [/STREAM]
  
  [STREAM]
  
  index=8
  
  codec_name=unknown
  
  codec_long_name=unknown
  
  profile=unknown
  
  codec_type=subtitle
  
  codec_time_base=1/1000
  
  codec_tag_string=[0][0][0][0]
  
  codec_tag=0x0000
  
  id=N/A
  
  r_frame_rate=0/0
  
  avg_frame_rate=0/0
  
  time_base=1/1000
  
  start_time=0.000000
  
  duration=N/A
  
  bit_rate=N/A
  
  nb_frames=N/A
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  TAG:language=fre
  
  TAG:title=french
  
  [/STREAM]
  
  [STREAM]
  
  index=9
  
  codec_name=unknown
  
  codec_long_name=unknown
  
  profile=unknown
  
  codec_type=subtitle
  
  codec_time_base=1/1000
  
  codec_tag_string=[0][0][0][0]
  
  codec_tag=0x0000
  
  id=N/A
  
  r_frame_rate=0/0
  
  avg_frame_rate=0/0
  
  time_base=1/1000
  
  start_time=0.000000
  
  duration=N/A
  
  bit_rate=N/A
  
  nb_frames=N/A
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  TAG:language=ger
  
  TAG:title=german
  
  [/STREAM]
  
  [STREAM]
  
  index=10
  
  codec_name=unknown
  
  codec_long_name=unknown
  
  profile=unknown
  
  codec_type=subtitle
  
  codec_time_base=1/1000
  
  codec_tag_string=[0][0][0][0]
  
  codec_tag=0x0000
  
  id=N/A
  
  r_frame_rate=0/0
  
  avg_frame_rate=0/0
  
  time_base=1/1000
  
  start_time=0.000000
  
  duration=N/A
  
  bit_rate=N/A
  
  nb_frames=N/A
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  TAG:language=nor
  
  TAG:title=norwegian
  
  [/STREAM]
  
  [STREAM]
  
  index=11
  
  codec_name=unknown
  
  codec_long_name=unknown
  
  profile=unknown
  
  codec_type=subtitle
  
  codec_time_base=1/1000
  
  codec_tag_string=[0][0][0][0]
  
  codec_tag=0x0000
  
  id=N/A
  
  r_frame_rate=0/0
  
  avg_frame_rate=0/0
  
  time_base=1/1000
  
  start_time=0.000000
  
  duration=N/A
  
  bit_rate=N/A
  
  nb_frames=N/A
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  TAG:language=spa
  
  TAG:title=spanish
  
  [/STREAM]
  
  [STREAM]
  
  index=12
  
  codec_name=unknown
  
  codec_long_name=unknown
  
  profile=unknown
  
  codec_type=subtitle
  
  codec_time_base=1/1000
  
  codec_tag_string=[0][0][0][0]
  
  codec_tag=0x0000
  
  id=N/A
  
  r_frame_rate=0/0
  
  avg_frame_rate=0/0
  
  time_base=1/1000
  
  start_time=0.000000
  
  duration=N/A
  
  bit_rate=N/A
  
  nb_frames=N/A
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  TAG:language=swe
  
  TAG:title=swedish
  
  [/STREAM]
  
  [STREAM]
  
  index=13
  
  codec_name=unknown
  
  codec_long_name=unknown
  
  profile=unknown
  
  codec_type=subtitle
  
  codec_time_base=1/1000
  
  codec_tag_string=[0][0][0][0]
  
  codec_tag=0x0000
  
  id=N/A
  
  r_frame_rate=0/0
  
  avg_frame_rate=0/0
  
  time_base=1/1000
  
  start_time=0.000000
  
  duration=N/A
  
  bit_rate=N/A
  
  nb_frames=N/A
  
  nb_read_frames=N/A
  
  nb_read_packets=N/A
  
  TAG:language=eng
  
  TAG:title=english hearig impaired
  
  [/STREAM]
  
  [FORMAT]
  
  filename=c:\dev\content\Breakfast At Tiffany's sample preview.mkv
  
  nb_streams=14
  
  format_name=matroska,webm
  
  format_long_name=Matroska/WebM file format
  
  start_time=0.000000
  
  duration=62.776000
  
  size=31947628
  
  bit_rate=4071317
  
  TAG:creation_time=2011-12-14 21:27:01
  
  [/FORMAT]

  My problem is, the process appears to hang. I took out the 'CreateNoWindow' option and, of course, I get a big blank window onscreen that normally just flashs by on a normal file. With the teletext subtitle file however, it persists. If I manually close it, the program continues and I seem to get the output I want.

  So my question is, how can I debug this further, to find out why this is hanging and how to handle the error (or simply ignore it) and continue ?