[FFmpeg-trac] #4674(ffmpeg:new): Allow to drop frames to keep A/V sync
FFmpeg
trac at avcodec.org
Fri Jun 26 12:37:10 CEST 2015
#4674: Allow to drop frames to keep A/V sync
---------------------------------------+--------------------------------
Reporter: cehoyos | Owner:
Type: enhancement | Status: new
Priority: wish | Component: ffmpeg
Version: git-master | Keywords: desync
Blocked By: | Blocking:
Reproduced by developer: 0 | Analyzed by developer: 0
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A user uploaded a HD recording of a Lumia cellphone which shows heavy A/v
desync issues with QT because audio has "holes" - especially noticeable
after 77 seconds. FFplay, MPlayer and WMP speed up video to keep A/V sync.
FFmpeg by default looses A/V sync, encoding with {{{-async 1}}} works fine
but produces silent moments.
There should be an option to drop video frames to keep A/V sync if another
stream is missing content, just like the media players skip these frames.
{{{
$ ffmpeg -i source2.mp4 -qscale 2 out.avi
ffmpeg version N-73169-gf5822ea Copyright (c) 2000-2015 the FFmpeg
developers
built with gcc 4.7 (SUSE Linux)
configuration: --enable-gpl
libavutil 54. 27.100 / 54. 27.100
libavcodec 56. 45.100 / 56. 45.100
libavformat 56. 38.102 / 56. 38.102
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 18.100 / 5. 18.100
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 2.100 / 1. 2.100
libpostproc 53. 3.100 / 53. 3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'source2.mp4':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: mp423gp6isomM4V
creation_time : 2015-06-20 18:05:00
encoder : 01
encoder-eng : 01
Duration: 00:01:34.38, start: 0.000000, bitrate: 17730 kb/s
Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv,
unknown/smpte170m/unknown), 1920x1080 [SAR 1:1 DAR 16:9], 17601 kb/s,
30.01 fps, 30 tbr, 30k tbn, 60 tbc (default)
Metadata:
creation_time : 2015-06-20 18:05:00
handler_name : VideoHandler
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono,
fltp, 153 kb/s (default)
Metadata:
creation_time : 2015-06-20 18:05:00
handler_name : AudioHandler
Please use -q:a or -q:v, -qscale is ambiguous
Output #0, avi, to 'out.avi':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: mp423gp6isomM4V
ISFT : Lavf56.38.102
Stream #0:0(und): Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 1920x1080
[SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 30 fps, 30 tbn, 30 tbc (default)
Metadata:
creation_time : 2015-06-20 18:05:00
handler_name : VideoHandler
encoder : Lavc56.45.100 mpeg4
Stream #0:1(und): Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, mono,
fltp, 96 kb/s (default)
Metadata:
creation_time : 2015-06-20 18:05:00
handler_name : AudioHandler
encoder : Lavc56.45.100 ac3
Stream mapping:
Stream #0:0 -> #0:0 (h264 (native) -> mpeg4 (native))
Stream #0:1 -> #0:1 (aac (native) -> ac3 (native))
Press [q] to stop, [?] for help
frame= 2826 fps=130 q=2.0 Lsize= 560532kB time=00:01:34.36
bitrate=48659.3kbits/s
video:559304kB audio:1082kB subtitle:0kB other streams:0kB global
headers:0kB muxing overhead: 0.026151%
}}}
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Ticket URL: <https://trac.ffmpeg.org/ticket/4674>
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