ffmpeg is generating an out-of-sync audio/video file
For those who may be trying this, I was better of recording flash in h264 right away, instead of using yuv420p for audio codec. That worked like a charm. Adding the flag -async 1
also helped.
Update: Check out this bit from the ffmpeg documentation (http://ffmpeg.org/ffmpeg.html):
-async: Audio sync method. "Stretches/squeezes" the audio stream to match the timestamps, the parameter is the maximum samples per second by which the audio is changed. -async 1 is a special case where only the start of the audio stream is corrected without any later correction. This option has been deprecated. Use the aresample audio filter instead.
You can read about the aresample filter here: http://ffmpeg.org/trac/ffmpeg/wiki/FilteringGuide
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marcelorocks
Full stack + mobile developer with a different passion for Python, Ruby, iOS Swift, Android and Javascript. Most of all, I love to ship products
Updated on July 09, 2022Comments
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marcelorocks almost 2 years
I am trying to convert a
flv
video tomp4
usinga264
, but the result video has a out of sync audio/video. The audio seems ok but the video seems slow and therefore out of sync with the audio.Here is the command I am running:
/opt/local/bin/ffmpeg -i complaint.flv -f mp4 -vcodec libx264 -acodec aac -copyts -strict experimental -fpre /opt/local/share/ffmpeg/libx264-lossless_slow.ffpreset -ab 44k -threads 0 -crf 23 complaint.mp4
And the output:
Desktop /opt/local/bin/ffmpeg -i complaint.flv -f mp4 -vcodec libx264 -acodec aac -copyts -strict experimental -fpre /opt/local/share/ffmpeg/libx264-lossless_slow.ffpreset -ab 44k -threads 0 -crf 23 complaint.mp4 ffmpeg version 0.7.8, Copyright (c) 2000-2011 the FFmpeg developers built on Jan 12 2012 21:12:26 with gcc 4.2.1 (Apple Inc. build 5666) (dot 3) configuration: --prefix=/opt/local --enable-gpl --enable-postproc --enable-swscale --enable-avfilter --enable-libmp3lame --enable-libvorbis --enable-libtheora --enable-libdirac --enable-libschroedinger --enable-libopenjpeg --enable-libxvid --enable-libx264 --enable-libvpx --enable-libspeex --mandir=/opt/local/share/man --enable-shared --enable-pthreads --cc=/usr/bin/gcc-4.2 --arch=x86_64 --enable-yasm libavutil 50. 43. 0 / 50. 43. 0 libavcodec 52.123. 0 / 52.123. 0 libavformat 52.111. 0 / 52.111. 0 libavdevice 52. 5. 0 / 52. 5. 0 libavfilter 1. 80. 0 / 1. 80. 0 libswscale 0. 14. 1 / 0. 14. 1 libpostproc 51. 2. 0 / 51. 2. 0 [flv @ 0x7fe57a04ac00] Estimating duration from bitrate, this may be inaccurate Input #0, flv, from 'complaint.flv': Metadata: duration : 7 creationdate : Thu Jan 12 23:47:24 description : Recorded using VideoRecording example. Duration: 00:00:06.61, start: 0.000000, bitrate: N/A Stream #0.0: Video: flv, yuv420p, 288x288, 1k tbr, 1k tbn, 1k tbc Stream #0.1: Audio: nellymoser, 11025 Hz, mono, s16 File 'complaint.mp4' already exists. Overwrite ? [y/N] y [buffer @ 0x7fe579c32cc0] w:288 h:288 pixfmt:yuv420p tb:1/1000000 sar:0/1 sws_param: [libx264 @ 0x7fe57a044600] using cpu capabilities: none! [libx264 @ 0x7fe57a044600] profile High, level 4.2 [libx264 @ 0x7fe57a044600] 264 - core 118 - H.264/MPEG-4 AVC codec - Copyleft 2003-2011 - http://www.videolan.org/x264.html - options: cabac=1 ref=2 deblock=1:0:0 analyse=0x3:0x33 me=umh subme=6 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=6 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=2 keyint=250 keyint_min=25 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=1.41 aq=1:1.00 Output #0, mp4, to 'complaint.mp4': Metadata: duration : 7 creationdate : Thu Jan 12 23:47:24 description : Recorded using VideoRecording example. encoder : Lavf52.111.0 Stream #0.0: Video: libx264, yuv420p, 288x288, q=0-69, 200 kb/s, 1k tbn, 1k tbc Stream #0.1: Audio: aac, 11025 Hz, mono, s16, 44 kb/s Stream mapping: Stream #0.0 -> #0.0 Stream #0.1 -> #0.1 Press [q] to stop, [?] for help frame= 6557 fps=106 q=-1.0 Lsize= 685kB time=00:00:03.62 bitrate=1549.1kbits/s dup=6367 drop=0 video:615kB audio:17kB global headers:0kB muxing overhead 8.361360% frame I:27 Avg QP:19.98 size: 8242 [libx264 @ 0x7fe57a044600] frame P:6530 Avg QP:30.71 size: 62 [libx264 @ 0x7fe57a044600] mb I I16..4: 11.1% 79.3% 9.6% [libx264 @ 0x7fe57a044600] mb P I16..4: 0.1% 0.2% 0.0% P16..4: 1.2% 0.2% 0.3% 0.0% 0.0% skip:98.0% [libx264 @ 0x7fe57a044600] 8x8 transform intra:77.8% inter:64.9% [libx264 @ 0x7fe57a044600] coded y,uvDC,uvAC intra: 75.3% 81.3% 33.3% inter: 0.5% 0.7% 0.1% [libx264 @ 0x7fe57a044600] i16 v,h,dc,p: 78% 9% 10% 3% [libx264 @ 0x7fe57a044600] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 35% 11% 32% 3% 4% 5% 2% 5% 4% [libx264 @ 0x7fe57a044600] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 56% 7% 9% 3% 4% 7% 3% 7% 3% [libx264 @ 0x7fe57a044600] i8c dc,h,v,p: 45% 15% 34% 6% [libx264 @ 0x7fe57a044600] Weighted P-Frames: Y:0.0% UV:0.0% [libx264 @ 0x7fe57a044600] ref P L0: 80.5% 9.5% 10.0% [libx264 @ 0x7fe57a044600] kb/s:767.20
Is there something I'm missing to make sure the video and audio line up perfectly?
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user1914692 about 11 years"in h264 right away, instead of using yuv420p for audio codec." ??? Do not understand. yuv420p is picture format, not video codec like h264, neither audio cedec. Then what did you do to get the sync?
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chovy about 7 yearsIs this the equivalent?
aresample=async=1
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Alex Sham over 3 yearsNot working for me. Webm -> mp4 still has video delay behind audio.
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andersonbd1 about 2 yearsThanks! "-async 1" did it for me.