[FFmpeg-trac] #692(undetermined:new): Audio is not in sync with video, webcam capturing

FFmpeg trac at avcodec.org
Mon Nov 28 03:13:42 CET 2011


#692: Audio is not in sync with video, webcam capturing
-------------------------------------+-------------------------------------
             Reporter:  burek        |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  important    |                Component:
              Version:  git-master   |  undetermined
             Keywords:               |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0
-------------------------------------+-------------------------------------

Comment (by burek):

 There were no errors in the output, that's why I didn't provide it, so
 here it is:

 {{{
 # ffmpeg -f video4linux2 -r 25 -s vga -i /dev/video0 -f alsa -ar 44100 -ac
 1 -i front:CARD=U0x46d0x809,DEV=0 -isync -vcodec libx264 -preset fast$

 ffmpeg version N-35149-g3880b45, Copyright (c) 2000-2011 the FFmpeg
 developers
   built on Nov 25 2011 02:16:49 with gcc 4.6.2
   configuration: --enable-static --enable-shared --enable-gpl --enable-
 nonfree --enable-postproc --enable-libx264 --enable-libaacplus --enable-
 libmp3lame --$
   libavutil    51. 28. 0 / 51. 28. 0
   libavcodec   53. 37. 0 / 53. 37. 0
   libavformat  53. 21. 0 / 53. 21. 0
   libavdevice  53.  4. 0 / 53.  4. 0
   libavfilter   2. 49. 0 /  2. 49. 0
   libswscale    2.  1. 0 /  2.  1. 0
   libpostproc  51.  2. 0 / 51.  2. 0
 [video4linux2,v4l2 @ 0x124ca20] Estimating duration from bitrate, this may
 be inaccurate
 Input #0, video4linux2,v4l2, from '/dev/video0':
   Duration: N/A, start: 865.119708, bitrate: 92160 kb/s
     Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 640x480,
 92160 kb/s, 25 tbr, 1000k tbn, 25 tbc
 [alsa @ 0x124da00] Estimating duration from bitrate, this may be
 inaccurate
 Input #1, alsa, from 'front:CARD=U0x46d0x809,DEV=0':
   Duration: N/A, start: 1322445758.231273, bitrate: N/A
     Stream #1:0: Audio: pcm_s16le, 48000 Hz, 1 channels, s16, 768 kb/s
 [buffer @ 0x124f040] w:640 h:480 pixfmt:yuv420p tb:1/1000000 sar:0/1
 sws_param:
 [libx264 @ 0x1247580] using cpu capabilities: MMX2 SSE2Fast SSSE3 Cache64
 [libx264 @ 0x1247580] profile High, level 3.0
 [mpegts @ 0x1247040] muxrate VBR, pcr every 2 pkts, sdt every 200, pat/pmt
 every 40 pkts
 Output #0, mpegts, to 'udp://burek:10001':
   Metadata:
     encoder         : Lavf53.21.0
     Stream #0:0: Video: h264, yuv420p, 640x480, q=-1--1, 90k tbn, 25 tbc
     Stream #0:1: Audio: aac, 48000 Hz, 1 channels, s16, 32 kb/s
 Stream mapping:
   Stream #0:0 -> #0:0 (rawvideo -> libx264)
   Stream #1:0 -> #0:1 (pcm_s16le -> libaacplus)
 Press [q] to stop, [?] for help
 frame=  373 fps= 24 q=25.0 Lsize=    2648kB time=00:00:14.46
 bitrate=1499.7kbits/s dup=155 drop=0
 video:2350kB audio:59kB global headers:0kB muxing overhead 9.917098%
 [libx264 @ 0x1247580] frame I:2     Avg QP:17.79  size: 23828
 [libx264 @ 0x1247580] frame P:306   Avg QP:19.51  size:  6459
 [libx264 @ 0x1247580] frame B:65    Avg QP:21.62  size:  5883
 [libx264 @ 0x1247580] consecutive B-frames: 66.5% 30.6%  0.8%  2.1%
 [libx264 @ 0x1247580] mb I  I16..4:  9.5% 78.3% 12.2%
 [libx264 @ 0x1247580] mb P  I16..4:  0.1%  0.9%  0.1%  P16..4: 39.7% 14.0%
 7.2%  0.0%  0.0%    skip:38.0%
 [libx264 @ 0x1247580] mb B  I16..4: 19.8% 19.3%  0.0%  B16..8:  9.2%  1.2%
 0.0%  direct:31.1%  skip:19.5%  L0:40.8% L1:48.1% BI:11.1%
 [libx264 @ 0x1247580] 8x8 transform intra:54.9% inter:75.2%
 [libx264 @ 0x1247580] coded y,uvDC,uvAC intra: 36.2% 100.0% 98.6% inter:
 24.4% 57.2% 43.1%
 [libx264 @ 0x1247580] i16 v,h,dc,p: 43% 19% 22% 15%
 [libx264 @ 0x1247580] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 19% 15% 40%  5%  4%
 4%  4%  5%  5%
 [libx264 @ 0x1247580] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 24% 25% 14%  7%  6%
 5%  6%  5%  7%
 [libx264 @ 0x1247580] i8c dc,h,v,p: 61% 21% 11%  7%
 [libx264 @ 0x1247580] Weighted P-Frames: Y:0.0% UV:0.0%
 [libx264 @ 0x1247580] ref P L0: 75.1% 24.9%
 [libx264 @ 0x1247580] ref B L0: 75.4% 24.6%
 [libx264 @ 0x1247580] kb/s:1290.40
 #
 }}}

 I always had problems with syncing audio and video with ffmpeg and webcam
 capturing, so I believe this might not be a regression.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/692#comment:2>
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