Recherche avancée

Sur d’autres sites (2718)

• Simply beyond ridiculous

  7 mai 2010, par Dark Shikari — H.265, speed

  For the past few years, various improvements on H.264 have been periodically proposed, ranging from larger transforms to better intra prediction. These finally came together in the JCT-VC meeting this past April, where over two dozen proposals were made for a next-generation video coding standard. Of course, all of these were in very rough-draft form ; it will likely take years to filter it down into a usable standard. In the process, they’ll pick the most useful features (hopefully) from each proposal and combine them into something a bit more sane. But, of course, it all has to start somewhere.

  A number of features were common : larger block sizes, larger transform sizes, fancier interpolation filters, improved intra prediction schemes, improved motion vector prediction, increased internal bit depth, new entropy coding schemes, and so forth. A lot of these are potentially quite promising and resolve a lot of complaints I’ve had about H.264, so I decided to try out the proposal that appeared the most interesting : the Samsung+BBC proposal (A124), which claims compression improvements of around 40%.

  The proposal combines a bouillabaisse of new features, ranging from a 12-tap interpolation filter to 12thpel motion compensation and transforms as large as 64×64. Overall, I would say it’s a good proposal and I don’t doubt their results given the sheer volume of useful features they’ve dumped into it. I was a bit worried about complexity, however, as 12-tap interpolation filters don’t exactly scream “fast”.

  I prepared myself for the slowness of an unoptimized encoder implementation, compiled their tool, and started a test encode with their recommended settings.

  I waited. The first frame, an I-frame, completed.

  I took a nap.

  I waited. The second frame, a P-frame, was done.

  I played a game of Settlers.

  I waited. The third frame, a B-frame, was done.

  I worked on a term paper.

  I waited. The fourth frame, a B-frame, was done.

  After a full 6 hours, 8 frames had encoded. Yes, at this rate, it would take a full two weeks to encode 10 seconds of HD video. On a Core i7. This is not merely slow ; this is over 1000 times slower than x264 on “placebo” mode. This is so slow that it is not merely impractical ; it is impossible to even test. This encoder is apparently designed for some sort of hypothetical future computer from space. And word from other developers is that the Intel proposal is even slower.

  This has led me to suspect that there is a great deal of cheating going on in the H.265 proposals. The goal of the proposals, of course, is to pick the best feature set for the next generation video compression standard. But there is an extra motivation : organizations whose features get accepted get patents on the resulting standard, and thus income. With such large sums of money in the picture, dishonesty becomes all the more profitable.

  There is a set of rules, of course, to limit how the proposals can optimize their encoders. If different encoders use different optimization techniques, the results will no longer be comparable — remember, they are trying to compare compression features, not methods of optimizing encoder-side decisions. Thus all encoders are required to use a constant quantizer, specified frame types, and so forth. But there are no limits on how slow an encoder can be or what algorithms it can use.

  It would be one thing if the proposed encoder was a mere 10 times slower than the current reference ; that would be reasonable, given the low level of optimization and higher complexity of the new standard. But this is beyond ridiculous. With the prize given to whoever can eke out the most PSNR at a given quantizer at the lowest bitrate (with no limits on speed), we’re just going to get an arms race of slow encoders, with every company trying to use the most ridiculous optimizations possible, even if they involve encoding the frame 100,000 times over to choose the optimal parameters. And the end result will be as I encountered here : encoders so slow that they are simply impossible to even test.

  Such an arms race certainly does little good in optimizing for reality where we don’t have 30 years to encode an HD movie : a feature that gives great compression improvements is useless if it’s impossible to optimize for in a reasonable amount of time. Certainly once the standard is finalized practical encoders will be written — but it makes no sense to optimize the standard for a use-case that doesn’t exist. And even attempting to “optimize” anything is difficult when encoding a few seconds of video takes weeks.

  Update : The people involved have contacted me and insist that there was in fact no cheating going on. This is probably correct ; the problem appears to be that the rules that were set out were simply not strict enough, making many changes that I would intuitively consider “cheating” to be perfectly allowed, and thus everyone can do it.

  I would like to apologize if I implied that the results weren’t valid ; they are — the Samsung-BBC proposal is definitely one of the best, which is why I picked it to test with. It’s just that I think any situation in which it’s impossible to test your own software is unreasonable, and thus the entire situation is an inherently broken one, given the lax rules, slow baseline encoder, and no restrictions on compute time.

• ffmpeg bit rate

  13 juillet 2012, par user1522872

  I am transcoding a video using FFMPEG API in c code.
  I am trying to set the video bit rate using the ffmpeg API as shown below :

  ovCodecCtx->bit_rate = 100 * 1000;

  The Encoder I am using is libx264.

  But this parameter is not taken into effect and the resulting video quality is very bad.
  I have even tried setting related parameters like rc_min_rate, rc_max_rate, etc.. but the video quality is still very low as these related parameters are not taken into effect.

  Could any expert tell how one can set the bit rate correctly using the FFMPEG API ?
  Thanks

• 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 ?