[FFmpeg-trac] #1259(undetermined:new): Audio sync issue

Sun Apr 29 18:25:01 CEST 2012

#1259: Audio sync issue
-------------------------------------+-------------------------------------
             Reporter:  burek        |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 From IRC channel:

 <Adys> Trying to record from webcam and keep audio in sync, this has audio
 running behind by 3-4 seconds
 <Adys> input comes from a separate usb mic if that makes any difference

 {{{
 % ffmpeg -f alsa -i pulse -f video4linux2 -s 800x600 -i /dev/video0 -sameq
 -acodec libmp3lame -ab 96k out.mkv
 ffmpeg version N-40213-g9f98a8e Copyright (c) 2000-2012 the FFmpeg
 developers
   built on Apr 29 2012 16:47:10 with gcc 4.7.0 20120414 (prerelease)
   configuration: --enable-libx264 --enable-nonfree --enable-libmp3lame
 --enable-libpulse --enable-gpl --disable-outdev=oss
   libavutil      51. 48.100 / 51. 48.100
   libavcodec     54. 17.100 / 54. 17.100
   libavformat    54.  3.100 / 54.  3.100
   libavdevice    53.  4.100 / 53.  4.100
   libavfilter     2. 72.100 /  2. 72.100
   libswscale      2.  1.100 /  2.  1.100
   libswresample   0. 11.100 /  0. 11.100
   libpostproc    52.  0.100 / 52.  0.100
 [alsa @ 0x279e100] Estimating duration from bitrate, this may be
 inaccurate
 Input #0, alsa, from 'pulse':
   Duration: N/A, start: 1335715213.308329, bitrate: 1536 kb/s
     Stream #0:0: Audio: pcm_s16le, 48000 Hz, 2 channels, s16, 1536 kb/s
 [video4linux2,v4l2 @ 0x279b3a0] Estimating duration from bitrate, this may
 be inaccurate
 Input #1, video4linux2,v4l2, from '/dev/video0':
   Duration: N/A, start: 67955.437449, bitrate: 153600 kb/s
     Stream #1:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 800x600,
 153600 kb/s, 20 tbr, 1000k tbn, 20 tbc
 [buffer @ 0x27a5100] w:800 h:600 pixfmt:yuyv422 tb:1/1000000 sar:0/1
 sws_param:flags=2
 [buffersink @ 0x279c9e0] auto-inserting filter 'auto-inserted scale 0'
 between the filter 'src' and the filter 'out'
 [scale @ 0x279d320] w:800 h:600 fmt:yuyv422 sar:0/1 -> w:800 h:600
 fmt:yuv422p sar:0/1 flags:0x4
 [libx264 @ 0x279a820] using cpu capabilities: MMX2 SSE2Fast SSSE3
 FastShuffle SSE4.2
 [libx264 @ 0x279a820] profile High 4:2:2, level 3.1, 4:2:2 8-bit
 [libx264 @ 0x279a820] 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=12
 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=20 scenecut=40
 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60
 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
 Guessed Channel Layout for  Input Stream #0.0 : stereo
 Output #0, matroska, to 'out.mkv':
   Metadata:
     encoder         : Lavf54.3.100
     Stream #0:0: Video: h264, yuv422p, 800x600, q=-1--1, 1k tbn, 20 tbc
     Stream #0:1: Audio: mp3, 48000 Hz, stereo, s16, 96 kb/s
 Stream mapping:
   Stream #1:0 -> #0:0 (rawvideo -> libx264)
   Stream #0:0 -> #0:1 (pcm_s16le -> libmp3lame)
 Press [q] to stop, [?] for help
 Input stream #0:0 frame changed from rate:48000 fmt:s16 ch:2 chl:0x0 to
 rate:48000 fmt:s16 ch:2 chl:0x3
 frame=   65 fps= 13 q=-1.0 Lsize=     871kB time=00:00:04.40
 bitrate=1622.4kbits/s
 video:782kB audio:87kB global headers:0kB muxing overhead 0.307903%
 [libx264 @ 0x279a820] frame I:1     Avg QP:23.90  size: 34621
 [libx264 @ 0x279a820] frame P:31    Avg QP:23.35  size: 17539
 [libx264 @ 0x279a820] frame B:33    Avg QP:25.02  size:  6721
 [libx264 @ 0x279a820] consecutive B-frames:  7.7% 64.6% 27.7%  0.0%
 [libx264 @ 0x279a820] mb I  I16..4: 18.5% 60.6% 20.9%
 [libx264 @ 0x279a820] mb P  I16..4:  1.7%  7.0%  1.4%  P16..4: 48.3% 18.1%
 13.3%  0.0%  0.0%    skip:10.0%
 [libx264 @ 0x279a820] mb B  I16..4:  0.3%  1.8%  0.3%  B16..8: 38.5%  4.8%
 1.2%  direct: 7.8%  skip:45.3%  L0:41.9% L1:49.5% BI: 8.7%
 [libx264 @ 0x279a820] 8x8 transform intra:67.8% inter:73.1%
 [libx264 @ 0x279a820] coded y,uvDC,uvAC intra: 65.6% 95.6% 80.9% inter:
 23.1% 58.6% 16.7%
 [libx264 @ 0x279a820] i16 v,h,dc,p: 17% 11%  2% 69%
 [libx264 @ 0x279a820] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 23% 12% 12%  8%  8%
 11%  7% 11%  9%
 [libx264 @ 0x279a820] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 25% 15% 12%  8%  9%
 10%  7%  8%  6%
 [libx264 @ 0x279a820] i8c dc,h,v,p: 45% 11% 24% 21%
 [libx264 @ 0x279a820] Weighted P-Frames: Y:3.2% UV:3.2%
 [libx264 @ 0x279a820] ref P L0: 53.4% 12.1% 22.5% 12.1%  0.0%
 [libx264 @ 0x279a820] ref B L0: 73.9% 24.6%  1.5%
 [libx264 @ 0x279a820] ref B L1: 95.1%  4.9%
 [libx264 @ 0x279a820] kb/s:1422.43
 }}}

 <burek> try lowering your video resolution to 320x240 just to see if it
 works
 <Adys> i get some weird speedup and lots of PTS 4254653, next:4716287
 invalid dropping st:0

 <burek> try: ffmpeg -f video4linux2 -s 320x240 -r 25 -i /dev/video0 -f
 alsa -i pulse -sameq -acodec libmp3lame -ab 96k out.mkv
 <Adys> no errors but sound still lagging about 1 second behind

 <Adys> using mp4 solves it, even works in 1280x720

 So, there is some kind of bug, when using alsa+video4linux2, which might
 be investigated a little bit, since a lot of people have reported syncing
 issues when capturing inputs from webcams (using video4linux2) + alsa
 audio.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1259>
FFmpeg <http://ffmpeg.org>
FFmpeg issue tracker