[FFmpeg-trac] #2771(undetermined:new): -segment_time generates unexpected file lengths

FFmpeg trac at avcodec.org
Wed Jul 10 19:18:13 CEST 2013


#2771: -segment_time generates unexpected file lengths
-------------------------------------+-------------------------------------
             Reporter:  Acc72        |                     Type:  defect
               Status:  new          |                 Priority:  important
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Hello,

 I'm attempting to utilize the segmenter on an A/V stream, from my USB
 webcam. With the -segment_time option, I've configured ffmpeg to output a
 circular series of four (4) mp4 files, each three (3) seconds in length.
 However, ffmpeg generates files which are sixteen (16) seconds in length.
 Occasionally, random files are generated at shorter lengths (2 sec, 3 sec,
 8 sec, etc...). However, most of them are generated sixteen (16) seconds
 in length.

 Results change, if I play with the value for -segment_time:
 (-Segment_time < 16) all 4 files generated @ 16 seconds.
 (-segment_time >= 16) 1st file generated @ 33 seconds and all subsequent
 files generated @ 16 seconds.

 Not sure why this is happening???

 Zeranoe official build: ffmpeg-20130706-git-63d7684-win32-static


 ffmpeg command line:
 {{{
 ffmpeg -f dshow -rtbufsize 10M -pix_fmt yuv420p -s 640x480 -ac 1 -i
 video="Logitech HD Webcam C310":audio="Microphone (HD Webcam C310)" -r 15
 -vcodec libx264 -preset fast -crf 22 -b:v 250k -acodec libvo_aacenc -ar 8k
 -b:a 96k -ac 1 -f segment -map 0 -reset_timestamps 1 -segment_time 3
 -segment_wrap 4 "out%2d.mp4"
 }}}

 Output:
 {{{
 ffmpeg version N-54499-g63d7684 Copyright (c) 2000-2013 the FFmpeg
 developers
   built on Jul  6 2013 10:30:06 with gcc 4.7.3 (GCC)
   configuration: --enable-gpl --enable-version3 --disable-w32threads
 --enable-avisynth --enable-bzlib --enable-fontconfig --enable-fr
 ei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray
 --enable-libcaca --enable-libfreetype --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-
 libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx
 --enable-libx264 --enable-libxavs --enable-libxvid --enable-z
 lib
   libavutil      52. 38.100 / 52. 38.100
   libavcodec     55. 18.102 / 55. 18.102
   libavformat    55. 11.101 / 55. 11.101
   libavdevice    55.  2.100 / 55.  2.100
   libavfilter     3. 78.102 /  3. 78.102
   libswscale      2.  3.100 /  2.  3.100
   libswresample   0. 17.102 /  0. 17.102
   libpostproc    52.  3.100 / 52.  3.100
 Guessed Channel Layout for  Input Stream #0.1 : mono
 Input #0, dshow, from 'video=Logitech HD Webcam C310:audio=Microphone (HD
 Webcam C310)':
   Duration: N/A, start: 76871.688000, bitrate: 705 kb/s
     Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 640x480, 30
 tbr, 10000k tbn, 30 tbc
     Stream #0:1: Audio: pcm_s16le, 44100 Hz, mono, s16, 705 kb/s
 [libx264 @ 04289b20] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2
 AVX
 [libx264 @ 04289b20] profile High, level 2.2
 [libx264 @ 04289b20] 264 - core 133 r2334 a3ac64b - H.264/MPEG-4 AVC codec
 - Copyleft 2003-2013 - http://www.videolan.org/x264.html -
  options: cabac=1 ref=2 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=6
 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 tre
 llis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2
 threads=6 lookahead_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=1 key
 int=250 keyint_min=15 scenecut=40 intra_refresh=0 rc_lookahead=30 rc=crf
 mbtree=1 crf=22.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ra
 tio=1.40 aq=1:1.00
 Output #0, segment, to 'out%2d.mp4':
   Metadata:
     encoder         : Lavf55.11.101
     Stream #0:0: Video: h264 (libx264), yuv420p, 640x480, q=-1--1, 250
 kb/s, 90k tbn, 15 tbc
     Stream #0:1: Audio: aac (libvo_aacenc), 8000 Hz, mono, s16, 96 kb/s
 Stream mapping:
   Stream #0:0 -> #0:0 (rawvideo -> libx264)
   Stream #0:1 -> #0:1 (pcm_s16le -> libvo_aacenc)
 Press [q] to stop, [?] for help
 frame= 1164 fps= 15 q=-1.0 Lsize=N/A time=00:01:17.46 bitrate=N/A dup=19
 drop=1131
 video:5204kB audio:101kB subtitle:0 global headers:0kB muxing overhead
 -100.000405%
 [libx264 @ 04289b20] frame I:5     Avg QP:16.94  size: 57563
 [libx264 @ 04289b20] frame P:331   Avg QP:20.45  size: 10496
 [libx264 @ 04289b20] frame B:828   Avg QP:23.23  size:  1891
 [libx264 @ 04289b20] consecutive B-frames:  0.9%  6.5% 19.1% 73.5%
 [libx264 @ 04289b20] mb I  I16..4:  2.3% 59.4% 38.3%
 [libx264 @ 04289b20] mb P  I16..4:  0.3%  2.4%  0.7%  P16..4: 49.4% 24.4%
 16.6%  0.0%  0.0%    skip: 6.3%
 [libx264 @ 04289b20] mb B  I16..4:  0.5%  0.6%  0.1%  B16..8: 17.0%  3.6%
 0.2%  direct:24.4%  skip:53.4%  L0:39.3% L1:43.2% BI:17.5%

 [libx264 @ 04289b20] 8x8 transform intra:61.3% inter:65.3%
 [libx264 @ 04289b20] coded y,uvDC,uvAC intra: 65.6% 95.7% 80.1% inter:
 15.6% 47.7% 14.1%
 [libx264 @ 04289b20] i16 v,h,dc,p: 17% 32% 37% 14%
 [libx264 @ 04289b20] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 12% 22% 26%  4%  7%
 6%  9%  6%  8%
 [libx264 @ 04289b20] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 17% 25% 10%  6%  9%
 8% 11%  7%  7%
 [libx264 @ 04289b20] i8c dc,h,v,p: 52% 22% 15% 11%
 [libx264 @ 04289b20] Weighted P-Frames: Y:2.7% UV:2.7%
 [libx264 @ 04289b20] ref P L0: 54.9% 45.1%
 [libx264 @ 04289b20] ref B L0: 69.7% 30.3%
 [libx264 @ 04289b20] ref B L1: 92.2%  7.8%
 [libx264 @ 04289b20] kb/s:549.25
 [dshow @ 0289c000] real-time buffer 74% full! frame dropped!
 }}}

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2771>
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