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• Difference between B-frame and b-frame when decoding x264

  11 mars 2016, par Pieter Verschaffelt

  I’m trying to achieve the following frame-pattern when encoding with the x264-encoder :

  IPBBPBBPBBPBBPBBI

  So, basically I want every 16th frame to be an I-frame and between every 2 P-frames there have to be 2 B-frames. I use these parameters :

  x264.exe -I 16 -i 16 --bframes 2 --b-adapt 0 --tune psnr --fps 25 --input-res 416x240

  But this gives an output of

  IPBbPBbPBbPBbPBbI

  What is the difference between an uppercase B or a lowercase b in this context ?

• Video frame difference with FFMPEG

  27 décembre 2015, par StepTNT

  I need to compute the frame differences between a source video and a compressed one.
  For now I’m using OpenCV with Java, by extracting each frame and doing a simple difference, but it’s quite slow (working a 0.5 fps, meaning that a 500 frames video will take more than 15 mins) so I was thinking to move to FFMPEG.

  FFMPEG feels a lot faster (everything’s done under 1 minute) but it has one big issue that makes the results useless : when compressing the source file, done with FFMPEG too, an extra gray frame is added at the beginning and this fakes the results because different frames are compared.

  This is what I’m doing now (knowing that the extra frame messes it all) :

  ffmpeg -y -i src.avi -i compressed.avi -filter_complex "blend=all_mode=difference,hue=s=0" -c:v libx264 -crf 18 -c:a copy difference.avi

  To fix the frame issue I was trying to remove the first frame by re-encoding the compressed video with this command

  ffmpeg -y -ss 0.02 -i compressed.mpg -an -f mpeg2video compressed-cut.mpg"

  (Note that -ss is 0.02 because it’s a 50 fps video, so I did 1/FPS as suggested here)

  But I get this response

  Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)

  So, finally, the question is : since extracting all the frames and then compute differences with OpenCV is really slow, how can I use FFMPEG to produce a video containing the difference between two sources while keeping in mind that one of them has an extra frame at the beginning ?

  EDIT : I wanted to avoid posting endless console outputs but since you asked for it, here we go.

  1) Encoding

  Input

  ffmpeg -i "720p50_mobcal_ter.avi" -an -f mpeg2video -y "720p50_mobcal_ter.mpg"

  Output

  ffmpeg version N-76684-g1fe82ab Copyright (c) 2000-2015 the FFmpeg developers
  
    built with gcc 5.2.0 (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-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-libzimg --enable-lzma --enable-decklink --enable-zlib
  
    libavutil      55.  6.100 / 55.  6.100
  
    libavcodec     57. 15.100 / 57. 15.100
  
    libavformat    57. 14.100 / 57. 14.100
  
    libavdevice    57.  0.100 / 57.  0.100
  
    libavfilter     6. 15.100 /  6. 15.100
  
    libswscale      4.  0.100 /  4.  0.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, avi, from '720p50_mobcal_ter.avi':
  
    Metadata:
  
      encoder         : Lavf57.14.100
  
    Duration: 00:00:10.08, start: 0.000000, bitrate: 552974 kb/s
  
      Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 1280x720, 554059 kb/s, SAR 1:1 DAR 16:9, 50 fps, 50 tbr, 50 tbn, 50 tbc
  
  Output #0, mpeg2video, to '720p50_mobcal_ter.mpg':
  
    Metadata:
  
      encoder         : Lavf57.14.100
  
      Stream #0:0: Video: mpeg2video, yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 50 fps, 50 tbn, 50 tbc
  
      Metadata:
  
        encoder         : Lavc57.15.100 mpeg2video
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (rawvideo (native) -> mpeg2video (native))
  
  Press [q] to stop, [?] for help
  
  frame=   41 fps=0.0 q=31.0 size=     984kB time=00:00:00.78 bitrate=10330.5kbits/frame=   80 fps= 78 q=31.0 size=    1323kB time=00:00:01.56 bitrate=6948.1kbits/frame=  124 fps= 80 q=31.0 size=    1725kB time=00:00:02.44 bitrate=5790.0kbits/frame=  168 fps= 81 q=31.0 size=    2084kB time=00:00:03.32 bitrate=5142.8kbits/frame=  212 fps= 81 q=31.0 size=    2482kB time=00:00:04.20 bitrate=4841.4kbits/frame=  255 fps= 82 q=31.0 size=    2840kB time=00:00:05.06 bitrate=4597.2kbits/frame=  296 fps= 82 q=31.0 size=    3133kB time=00:00:05.88 bitrate=4364.5kbits/frame=  338 fps= 82 q=24.8 size=    3453kB time=00:00:06.72 bitrate=4209.2kbits/frame=  382 fps= 82 q=31.0 size=    3723kB time=00:00:07.60 bitrate=4013.4kbits/frame=  426 fps= 83 q=31.0 size=    4005kB time=00:00:08.48 bitrate=3869.1kbits/frame=  470 fps= 83 q=24.8 size=    4276kB time=00:00:09.36 bitrate=3742.5kbits/frame=  504 fps= 83 q=31.0 Lsize=    4469kB time=00:00:10.06 bitrate=3639.3kbits/s
  
  video:4469kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000000%

  This adds the extra grey frame at the beginning, it just duplicates the first one

  2) Removing first frame

  Input

  ffmpeg -y -i "720p50_mobcal_ter.mpg" -an -f mpeg2video -vf select=gte(n\,1) "CUT-720p50_mobcal_ter.mpg"

  Output

  ffmpeg version N-76684-g1fe82ab Copyright (c) 2000-2015 the FFmpeg developers
  
    built with gcc 5.2.0 (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-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-libzimg --enable-lzma --enable-decklink --enable-zlib
  
    libavutil      55.  6.100 / 55.  6.100
  
    libavcodec     57. 15.100 / 57. 15.100
  
    libavformat    57. 14.100 / 57. 14.100
  
    libavdevice    57.  0.100 / 57.  0.100
  
    libavfilter     6. 15.100 /  6. 15.100
  
    libswscale      4.  0.100 /  4.  0.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, mpegvideo, from '720p50_mobcal_ter.mpg':
  
    Duration: N/A, bitrate: N/A
  
      Stream #0:0: Video: mpeg2video (Main), yuv420p(tv), 1280x720 [SAR 1:1 DAR 16:9], max. 104857 kb/s, 50 fps, 50 tbr, 1200k tbn, 100 tbc
  
  Output #0, mpeg2video, to 'CUT-720p50_mobcal_ter.mpg':
  
    Metadata:
  
      encoder         : Lavf57.14.100
  
      Stream #0:0: Video: mpeg2video, yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 50 fps, 50 tbn, 50 tbc
  
      Metadata:
  
        encoder         : Lavc57.15.100 mpeg2video
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (mpeg2video (native) -> mpeg2video (native))
  
  Press [q] to stop, [?] for help
  
  frame=  255 fps=0.0 q=31.0 size=    2781kB time=00:00:05.10 bitrate=4467.3kbits/frame=  503 fps=0.0 q=31.0 Lsize=    4415kB time=00:00:10.08 bitrate=3588.5kbits/s
  
  video:4415kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000000%

  3) Frame difference

  Input

  ffmpeg -y -i "720p50_mobcal_ter.avi" -i "CUT-720p50_mobcal_ter.mpg" -filter_complex "blend=all_mode=difference,hue=s=0" -c:v libx264 -crf 18 -c:a copy "DIFF-720p50_mobcal_ter.mpg"

  Output

  ffmpeg version N-76684-g1fe82ab Copyright (c) 2000-2015 the FFmpeg developers
  
    built with gcc 5.2.0 (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-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-libzimg --enable-lzma --enable-decklink --enable-zlib
  
    libavutil      55.  6.100 / 55.  6.100
  
    libavcodec     57. 15.100 / 57. 15.100
  
    libavformat    57. 14.100 / 57. 14.100
  
    libavdevice    57.  0.100 / 57.  0.100
  
    libavfilter     6. 15.100 /  6. 15.100
  
    libswscale      4.  0.100 /  4.  0.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, avi, from '720p50_mobcal_ter.avi':
  
    Metadata:
  
      encoder         : Lavf57.14.100
  
    Duration: 00:00:10.08, start: 0.000000, bitrate: 552974 kb/s
  
      Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 1280x720, 554059 kb/s, SAR 1:1 DAR 16:9, 50 fps, 50 tbr, 50 tbn, 50 tbc
  
  Input #1, mpegvideo, from 'CUT-720p50_mobcal_ter.mpg':
  
    Duration: N/A, bitrate: N/A
  
      Stream #1:0: Video: mpeg2video (Main), yuv420p(tv), 1280x720 [SAR 1:1 DAR 16:9], max. 104857 kb/s, 50 fps, 50 tbr, 1200k tbn, 100 tbc
  
  [libx264 @ 000002784dbeb980] using SAR=1/1
  
  [libx264 @ 000002784dbeb980] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
  
  [libx264 @ 000002784dbeb980] profile High, level 3.2
  
  [mpeg @ 000002784dbeaf20] VBV buffer size not set, using default size of 130KB
  
  If you want the mpeg file to be compliant to some specification
  
  Like DVD, VCD or others, make sure you set the correct buffer size
  
  Output #0, mpeg, to 'D:\DOWNLOADS\TMP\Video TDI\AVI\DIFF-720p50_mobcal_ter.mpg':
  
    Metadata:
  
      encoder         : Lavf57.14.100
  
      Stream #0:0: Video: h264 (libx264), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=-1--1, 50 fps, 90k tbn, 50 tbc (default)
  
      Metadata:
  
        encoder         : Lavc57.15.100 libx264
  
  Stream mapping:
  
    Stream #0:0 (rawvideo) -> blend:top
  
    Stream #1:0 (mpeg2video) -> blend:bottom
  
    hue -> Stream #0:0 (libx264)
  
  Press [q] to stop, [?] for help
  
  frame=  504 fps= 39 q=-1.0 Lsize=   32182kB time=00:00:10.04 bitrate=26258.5kbits/s
  
  video:32061kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.377054%
  
  [libx264 @ 000002784dbeb980] frame I:30    Avg QP:19.69  size:149974
  
  [libx264 @ 000002784dbeb980] frame P:299   Avg QP:23.28  size: 69423
  
  [libx264 @ 000002784dbeb980] frame B:175   Avg QP:24.48  size: 43280
  
  [libx264 @ 000002784dbeb980] consecutive B-frames: 30.6% 69.4%  0.0%  0.0%
  
  [libx264 @ 000002784dbeb980] mb I  I16..4: 18.3% 51.4% 30.4%
  
  [libx264 @ 000002784dbeb980] mb P  I16..4:  0.6%  5.6%  2.4%  P16..4: 35.9% 22.9% 15.6%  0.0%  0.0%    skip:17.0%
  
  [libx264 @ 000002784dbeb980] mb B  I16..4:  0.2%  0.5%  0.3%  B16..8: 49.5% 12.4%  5.6%  direct:15.5%  skip:16.1%  L0:47.8% L1:42.1% BI:10.1%
  
  [libx264 @ 000002784dbeb980] 8x8 transform intra:57.5% inter:38.5%
  
  [libx264 @ 000002784dbeb980] coded y,uvDC,uvAC intra: 90.7% 0.0% 0.0% inter: 50.3% 0.0% 0.0%
  
  [libx264 @ 000002784dbeb980] i16 v,h,dc,p: 32% 23% 35% 10%
  
  [libx264 @ 000002784dbeb980] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 11% 11% 41%  7%  5%  6%  5%  6%  8%
  
  [libx264 @ 000002784dbeb980] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 18% 14% 23%  8%  7%  7%  7%  7%  8%
  
  [libx264 @ 000002784dbeb980] i8c dc,h,v,p: 100%  0%  0%  0%
  
  [libx264 @ 000002784dbeb980] Weighted P-Frames: Y:33.8% UV:0.0%
  
  [libx264 @ 000002784dbeb980] ref P L0: 58.1% 16.3% 14.2%  9.4%  2.0%
  
  [libx264 @ 000002784dbeb980] ref B L0: 79.3% 20.7%
  
  [libx264 @ 000002784dbeb980] kb/s:26056.02

  The second command made everything work while the second one in the first part didn’t (the one with the -ss option), so I could be quite happy about it but I’m not that sure if FFMPEG duplicates the first frame for every video or if it’s just related to the one I’m using now, so it could be better to start off with a compressed video that has the same frame count of the original one.

  So let’s get to one final question : why does FFMPEG add a duplicated first frame at the beginning of the compressed video and how can I avoid that ?

• FFmpeg : what's the difference betwen av_opt_set and av_dict_set ?

  16 novembre 2015, par Nyaruko

  What is the difference av_opt_setxx and av_dict_set,
  according to what I have found, if you want to set things like

  rtbuffersize

  or

  rtsp_transport

  , you use the av_dict_set.

  Can I set all options through av_dict_set ? If so, what’s the purpose of av_opt_set ?