[FFmpeg-trac] #1664(FFmpeg:new): Transcoding results in dropped frames and lowering fps

FFmpeg trac at avcodec.org
Sun Aug 19 23:55:46 CEST 2012


#1664: Transcoding results in dropped frames and lowering fps
----------------------------------+--------------------------------------
             Reporter:  Barvinok  |                     Type:  defect
               Status:  new       |                 Priority:  normal
            Component:  FFmpeg    |                  Version:  git-master
             Keywords:            |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
----------------------------------+--------------------------------------
 Summary of the bug:

 The input video file is recorded by SonyEricsson Xperia X2 camera, has an
 extension MP4 and contain "aac mp4a" and "mpeg4 (Simple Profile)"
 according to ffprobe (see below).

 I wanted to convert it using libx264/libvorbis as encoders and matroska as
 container. The command I used was:
 {{{
 /opt/ffmpeg/bin/ffmpeg -i 00-00-00-00000001.mp4 \
 -vcodec libx264 -crf 22 \
 -acodec libvorbis -ab 64k test.mkv
 }}}
 The actual invocation is a bit longer, but this one is for reproducing the
 effect. At first glance, ffmpeg seemed to process it all right:
 {{{
 ffmpeg version N-43733-ga93c221 Copyright (c) 2000-2012 the FFmpeg
 developers
   built on Aug 19 2012 21:27:54 with gcc 4.5.3 (Gentoo 4.5.3-r2 p1.1,
 pie-0.4.7)
   configuration: --prefix=/opt/ffmpeg --libdir=/usr/lib64
 --shlibdir=/usr/lib64 --mandir=/usr/share/man --enable-shared --cc=x86_64
 -pc-linux-gnu-gcc --cxx=x86_64-pc-linux-gnu-g++ --ar=x86_64-pc-linux-gnu-
 ar --optflags='-march=native -mtune=native -O2 -pipe -mmmx -msse -msse2
 -msse4a -m3dnow -fomit-frame-pointer -funroll-loops' --extra-
 cflags='-march=native -mtune=native -O2 -pipe -mmmx -msse -msse2 -msse4a
 -m3dnow -fomit-frame-pointer -funroll-loops' --extra-
 cxxflags='-march=native -mtune=native -O2 -pipe -mmmx -msse -msse2 -msse4a
 -m3dnow -fomit-frame-pointer -funroll-loops' --disable-static --enable-gpl
 --enable-version3 --enable-postproc --enable-avfilter --disable-stripping
 --disable-debug --disable-doc --disable-network --disable-vaapi --disable-
 vdpau --disable-ffplay --enable-gnutls --enable-libmp3lame --enable-libvo-
 aacenc --enable-libvo-amrwbenc --enable-libtheora --enable-libvorbis
 --enable-libx264 --enable-libxvid --disable-indev=v4l --disable-indev=v4l2
 --disable-indev=alsa --disable-indev=oss
   libavutil      51. 70.100 / 51. 70.100
   libavcodec     54. 53.100 / 54. 53.100
   libavformat    54. 25.104 / 54. 25.104
   libavdevice    54.  2.100 / 54.  2.100
   libavfilter     3. 11.101 /  3. 11.101
   libswscale      2.  1.101 /  2.  1.101
   libswresample   0. 15.100 /  0. 15.100
   libpostproc    52.  0.100 / 52.  0.100
 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '00-00-00-00000001.mp4':
   Metadata:
     major_brand     : isom
     minor_version   : 0
     compatible_brands: mp41isom
     creation_time   : 1980-01-17 22:55:01
   Duration: 00:00:59.54, start: 0.000000, bitrate: 1168 kb/s
     Stream #0:0(eng): Audio: aac (mp4a / 0x6134706D), 16000 Hz, mono, s16,
 23 kb/s
     Metadata:
       creation_time   : 1980-01-17 22:55:01
       handler_name    : AudioHandler
     Stream #0:1(eng): Video: mpeg4 (Simple Profile) (mp4v / 0x7634706D),
 yuv420p, 640x480 [SAR 1:1 DAR 4:3], 1142 kb/s, 26.79 fps, 15 tbr, 1k tbn,
 15 tbc
     Metadata:
       creation_time   : 1980-01-17 22:55:01
       handler_name    : VideoHandler
 [libx264 @ 0x1010bc0] using SAR=1/1
 [libx264 @ 0x1010bc0] using cpu capabilities: MMX2 SSE2Fast FastShuffle
 SSEMisalign LZCNT
 [libx264 @ 0x1010bc0] profile High, level 2.2
 [libx264 @ 0x1010bc0] 264 - core 120 - H.264/MPEG-4 AVC codec - Copyleft
 2003-2011 - http://www.videolan.org/x264.html - options: cabac=1 ref=3
 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00
 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0
 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=1 sliced_threads=0
 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3
 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2
 keyint=250 keyint_min=15 scenecut=40 intra_refresh=0 rc_lookahead=40
 rc=crf mbtree=1 crf=22.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4
 ip_ratio=1.40 aq=1:1.00
 Output #0, matroska, to 'test.mkv':
   Metadata:
     major_brand     : isom
     minor_version   : 0
     compatible_brands: mp41isom
     encoder         : Lavf54.25.104
     Stream #0:0(eng): Video: h264, yuv420p, 640x480 [SAR 1:1 DAR 4:3],
 q=-1--1, 1k tbn, 15 tbc
     Metadata:
       creation_time   : 1980-01-17 22:55:01
       handler_name    : VideoHandler
     Stream #0:1(eng): Audio: vorbis, 16000 Hz, mono, flt, 64 kb/s
     Metadata:
       creation_time   : 1980-01-17 22:55:01
       handler_name    : AudioHandler
 Stream mapping:
   Stream #0:1 -> #0:0 (mpeg4 -> libx264)
   Stream #0:0 -> #0:1 (aac -> libvorbis)
 Press [q] to stop, [?] for help
 Que input is backward in timeze=       5kB time=00:00:00.00 bitrate=
 0.0kbits/s dup=0 drop=28
 frame=  892 fps=9.8 q=26.0 Lsize=    7511kB time=00:00:57.91
 bitrate=1062.5kbits/s dup=0 drop=703
 video:7258kB audio:229kB subtitle:0 global headers:4kB muxing overhead
 0.265491%
 [libx264 @ 0x1010bc0] frame I:4     Avg QP:18.68  size: 21682
 [libx264 @ 0x1010bc0] frame P:817   Avg QP:21.72  size:  8581
 [libx264 @ 0x1010bc0] frame B:71    Avg QP:24.38  size:  4714
 [libx264 @ 0x1010bc0] consecutive B-frames: 85.0% 12.3%  2.7%  0.0%
 [libx264 @ 0x1010bc0] mb I  I16..4: 14.3% 77.7%  8.0%
 [libx264 @ 0x1010bc0] mb P  I16..4:  2.5%  8.0%  0.5%  P16..4: 55.0% 20.5%
 9.5%  0.0%  0.0%    skip: 4.1%
 [libx264 @ 0x1010bc0] mb B  I16..4:  0.7%  2.5%  0.1%  B16..8: 42.9%  9.4%
 2.0%  direct:15.4%  skip:26.9%  L0:48.3% L1:31.7% BI:20.0%
 [libx264 @ 0x1010bc0] 8x8 transform intra:73.4% inter:75.0%
 [libx264 @ 0x1010bc0] coded y,uvDC,uvAC intra: 61.8% 90.1% 45.1% inter:
 42.7% 68.5% 9.9%
 [libx264 @ 0x1010bc0] i16 v,h,dc,p: 26% 33% 15% 25%
 [libx264 @ 0x1010bc0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 19% 26% 29%  3%  4%
 4%  6%  3%  5%
 [libx264 @ 0x1010bc0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 25% 29% 15%  3%  7%
 6%  7%  4%  4%
 [libx264 @ 0x1010bc0] i8c dc,h,v,p: 46% 28% 20%  6%
 [libx264 @ 0x1010bc0] Weighted P-Frames: Y:6.2% UV:0.9%
 [libx264 @ 0x1010bc0] ref P L0: 73.7% 18.0%  6.1%  2.0%  0.1%
 [libx264 @ 0x1010bc0] ref B L0: 91.5%  8.2%  0.3%
 [libx264 @ 0x1010bc0] ref B L1: 98.6%  1.4%
 [libx264 @ 0x1010bc0] kb/s:996.45
 }}}
 What worried me is the discrepancy between reported fps and tbr in the
 original stream, also of note was the large quantity of the dropped frames
 - nearly half of them.

 And indeed, while the original material had FPS of roughly 26, the
 converted file displayed FPS of 15, hence the dropped frames, though I did
 not specify -r option. And the difference in FPS is clearly visible by
 naked eye.

 Expected: I expected ffmpeg to preserve the FPS of the original material
 in the absence of -r option.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1664>
FFmpeg <http://ffmpeg.org>
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