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• FFmpeg first frame byte size over 2x size compared to all other frames - w/ 100% keyframes

  22 juillet 2016, par Dustin Kerstein

  I’m encoding an h264 mp4 and am having a small issue with the output byte size of the first frame vs. all other frames. There’s no frame duplication happening, rather just that the first frame always ends up being 2x the byte size of other frames. My use-case requires that the first frame be very similar in size compared to other frame.

  Here are the ffmpeg encoding parameters :

  ffmpeg -framerate 60 -i "C:\Test%4d.jpg" -c:v libx264 -g 1 -vf "scale=3840:2160" -crf 19 -pix_fmt yuv420p C:\Test.mp4

  And the frame details using ffprobe :

  ffprobe C:\Test.mp4 -show_frames -of compact -show_entries frame=pict_type,pkt_size
  
  
  
  ffprobe version N-79143-g8ff0f6a Copyright (c) 2007-2016 the FFmpeg developers
  
    built with gcc 5.3.0 (GCC)
  
    configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmfx --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib
  
    libavutil      55. 19.100 / 55. 19.100
  
    libavcodec     57. 30.100 / 57. 30.100
  
    libavformat    57. 29.101 / 57. 29.101
  
    libavdevice    57.  0.101 / 57.  0.101
  
    libavfilter     6. 40.102 /  6. 40.102
  
    libswscale      4.  0.100 /  4.  0.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'C:\users\dusti\downloads\Test.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.29.101
  
    Duration: 00:00:00.17, start: 0.000000, bitrate: 240225 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 3840x2160 [SAR 9:16 DAR 1:1], 240662 kb/s, 60 fps, 60 tbr, 15360 tbn, 120 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
  frame|pkt_size=1377043|pict_type=I
  
  frame|pkt_size=406953|pict_type=I
  
  frame|pkt_size=407200|pict_type=I
  
  frame|pkt_size=406647|pict_type=I
  
  frame|pkt_size=405276|pict_type=I
  
  frame|pkt_size=404715|pict_type=I
  
  frame|pkt_size=403226|pict_type=I
  
  frame|pkt_size=401806|pict_type=I
  
  frame|pkt_size=400750|pict_type=I
  
  frame|pkt_size=400189|pict_type=I

  I’ve confirmed that it’s not just a reporting issue with ffprobe by converting the file with mp4box :

  mp4box.exe -dash 16.666 -frag 16.666 -rap c:\Test.mp4

  Which returns an MPD file :

  <initialization range="0-922"></initialization>
  
        <segmenturl mediarange="923-1378146" indexrange="923-966"></segmenturl>
  
        <segmenturl mediarange="1378147-1785280" indexrange="1378147-1378190"></segmenturl>
  
        <segmenturl mediarange="1785281-2192661" indexrange="1785281-1785324"></segmenturl>
  
        <segmenturl mediarange="2192662-2599489" indexrange="2192662-2192705"></segmenturl>
  
        <segmenturl mediarange="2599490-3004946" indexrange="2599490-2599533"></segmenturl>
  
        <segmenturl mediarange="3004947-3409842" indexrange="3004947-3004990"></segmenturl>
  
        <segmenturl mediarange="3409843-3813249" indexrange="3409843-3409886"></segmenturl>
  
        <segmenturl mediarange="3813250-4215236" indexrange="3813250-3813293"></segmenturl>
  
        <segmenturl mediarange="4215237-4616167" indexrange="4215237-4215280"></segmenturl>
  
        <segmenturl mediarange="4616168-5016537" indexrange="4616168-4616211"></segmenturl>
  
      

  I tried encoding a dummy black frame and it does seem to work around the issue but I’d really prefer to not do that. Here are the frame sizes with the first frame replaced by a pure black frame :

  frame|pkt_size=2173|pict_type=I
  
  frame|pkt_size=466255|pict_type=I
  
  frame|pkt_size=430179|pict_type=I
  
  frame|pkt_size=416652|pict_type=I
  
  frame|pkt_size=411401|pict_type=I
  
  frame|pkt_size=407174|pict_type=I
  
  frame|pkt_size=405377|pict_type=I
  
  frame|pkt_size=403207|pict_type=I
  
  frame|pkt_size=401588|pict_type=I
  
  frame|pkt_size=401200|pict_type=I

  Anyone have any clues on how to control this behavior ? I imagine it might have something to do with the CRF quality algorithm but really have no idea. Any help would be appreciated.

  Thanks,
  Dustin

  Update 7/22/16
  Upon a little more digging I can see that ffmpeg is using a lower QP for the first frame :

  [libx264 @ 05380b60] frame=   0 QP=14.92 NAL=3 Slice:I Poc:0   I:32400 P:0    SKIP:0    size=1485053 bytes
  
  [libx264 @ 05380b60] frame=   1 QP=29.48 NAL=3 Slice:I Poc:0   I:32400 P:0    SKIP:0    size=361196 bytes
  
  [libx264 @ 05380b60] frame=   2 QP=29.48 NAL=3 Slice:I Poc:0   I:32400 P:0    SKIP:0    size=359406 bytes

  But I’ve still not found a way to avoid this behavior. I tried setting qpmin/qpmax to non-default values but that didn’t change anything. Per my comment below, two-pass encoding does not exhibit this behavior. Still looking for a way to use CRF encoding without this large initial frame.

• GNU Radio + leandvb demodulation of DVB-S signals

  25 juillet 2016, par ShatteredPheonix

  I am new to signal processing and RF, however I am trying to receive Ham TV signals from the ISS in gnu radio and then demodulate them using leandvb so that I can playback the video through a standard player like VLC.

  So please excuse my incorrect terminology where used :

  I have the following GNU Radio Setup :
  

  A few things about the file I am using is that it was recorded at 1msps with a symbol rate of 1 which was done via USRP.

  After playing the flow graph this seem to be the result :
  

  The above image, to me looks like a fairly clean signal - in addition to this I can’t seem to clear it up anymore.

  However, when I put it through a DVB-S demodulater called leandvb it can’t seem to get any TS packets out.

  instead it reports :

  rawiq            : 1647M/549M   2048 writable  ,   2048 unread ( 0 
  
  2048 2048 )
  
  autonotched      : 2197M/549M   3072 writable !,   1024 unread ( 0 0 1024 0 )
  
  PSK symbols      : 955M/477M   4057 writable  ,   4870 unread ( 373 4870 )
  
  freq             :   0M/  0M      2 writable  ,      0 unread ( 0 )
  
  bytes            :   0M/  0M   9792 writable  ,      0 unread ( 0 )
  
  RS-enc packets   :   0M/  0M      4 writable  ,      0 unread ( 0 )
  
  rand TS packets  :   0M/  0M      4 writable  ,      0 unread ( 0 )
  
  TS packets       :   0M/  0M      4 writable  ,      0 unread ( 0 0 )
  
  SS               :   0M/  0M      1 writable  ,      1 unread ( 1 )
  
  packet counter   :   0M/  0M    400 writable  ,      0 unread ( 0 )
  
  Total buffer memory: 422 KiB

  it seems to have problems reading some symbols and raw data but I don’t know why and I have tried almost everything I can think of to get it work.

  and when I try to play the resulting ts file through mplayer / ffmpeg / ffplay / vlc I get various errors :

  • File does not contain Stream
  • Invalid data while preprocessing
  • Cannot prefill buffer

  Can anyone help me and tell me where I am going wrong ? As I am completely clueless and have been trying to solve this problem for about 2 weeks now ?

• Why the fps of concatenate video file change with old video file ?

  23 juin 2016, par Zuiche

  I have two wmv video file which 25fps.
  I concatenate these video file using ffmpeg command line like this :

  ffmpeg -r 25 -f concat -i 1.txt -c copy output.wmv

  1.txt :

  file 'g:\1.wmv'
  
  file 'g:\2.wmv' 

  It works. But the fps of output.wmv is 30.
  How can I maintain the fps of concatenate video file ?

  UPDATE
  ======Console Output========

  ffmpeg version N-73266-g4aa0de6 Copyright (c) 2000-2015 the FFmpeg developers
  
  built with gcc 4.9.2 (GCC)
  
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-lzma --enable-decklink --enable-zlib
  
  libavutil      54. 27.100 / 54. 27.100
  
  libavcodec     56. 45.101 / 56. 45.101
  
  libavformat    56. 40.100 / 56. 40.100
  
  libavdevice    56.  4.100 / 56.  4.100
  
  libavfilter     5. 19.100 /  5. 19.100
  
  libswscale      3.  1.101 /  3.  1.101
  
  libswresample   1.  2.100 /  1.  2.100
  
  libpostproc    53.  3.100 / 53.  3.100
  
  [wmv3 @ 04d452a0] Extra data: 8 bits left, value: 20
  
  [wmv3 @ 04d14d00] Extra data: 8 bits left, value: 20
  
  Input #0, concat, from '1.txt':
  
  Duration: N/A, start: 0.000000, bitrate: 4214 kb/s
  
  Stream #0:0: Video: wmv3 (Main) (WMV3 / 0x33564D57), yuv420p, 720x576, 4194 kb/s, SAR 16:15 DAR 4:3, 25 fps, 25 tbr, 1k tbn, 1k tbc
  
  Stream #0:1: Audio: wmavoice ([10][0][0][0] / 0x000A), 22050 Hz, mono, flt, 20 kb/s
  
  [asf @ 04d12120] Codec for stream 0 does not use global headers but container format requires global headers
  
  [asf @ 04d12120] Codec for stream 1 does not use global headers but container format requires global headers
  
  Output #0, asf, to 'output.wmv':
  
  Metadata:
  
  WM/EncodingSettings: Lavf56.40.100
  
  Stream #0:0: Video: wmv3 (WMV3 / 0x33564D57), yuv420p, 720x576 [SAR 16:15 DAR 4:3], q=2-31, 4194 kb/s, 25 fps, 25 tbr, 1k tbn, 25 tbc
  
  Stream #0:1: Audio: wmavoice ([10][0][0][0] / 0x000A), 22050 Hz, mono, 20 kb/s
  
  Stream mapping:
  
  Stream #0:0 -> #0:0 (copy)
  
  Stream #0:1 -> #0:1 (copy)
  
  Press [q] to stop, [?] for help
  
  [wmv3 @ 04ce8880] Extra data: 8 bits left, value: 20
  
  frame=  538 fps=0.0 q=-1.0 Lsize=    5723kB time=00:00:21.52 bitrate=2178.5kbits/s  
  
  video:5593kB audio:62kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.206905%

  =========FFprobe Output=========

  ffprobe version N-60456-g4040b56-Sherpya Copyright (c) 2007-2014 the FFmpeg developers
  
  built on Feb  9 2014 06:50:33 with gcc 4.8 (GCC)
  
  [wmv3 @ 050684e0] Extra data: 8 bits left, value: 20
  
  Input #0, asf, from 'output.wmv':
  
  Metadata:
  
  encoder         : Lavf56.40.100
  
  Duration: 00:00:21.52, start: 0.000000, bitrate: 2178 kb/s
  
  Stream #0:0: Video: wmv3 (Main) (WMV3 / 0x33564D57), yuv420p, 720x576, SAR 16:15 DAR 4:3, 25 tbr, 1k tbn, 1k tbc
  
  Stream #0:1: Audio: wmavoice ([10][0][0][0] / 0x000A), 22050 Hz, mono, flt, 20 kb/s
  
  [wmv3 @ 050684e0] Extra data: 8 bits left, value: 20