Carl Eugen Hoyos <[email protected]> added the comment:
While I tested alsa instead of oss and I cannot reproduce a "wrong fps" problem,
there is something wrong if I wait before answering "y" on "Overwrite?" when
using video4linux(2)/audio input:
The resulting stream has wrong timestamps, so that MPlayer shows a still frame,
ffplay incorrectly shows desync in the status line (according to the time
waited), and seeking with ffplay leads to desync (that's for waiting ~10
seconds, less waiting just leads to desync on playback).
ffmpeg -f alsa -ac 2 -i hw:2 -f video4linux2 -i /dev/video0 -r 25 test.avi
FFmpeg version SVN-r24514, Copyright (c) 2000-2010 the FFmpeg developers
built on Jul 27 2010 13:07:02 with gcc 4.4.4
configuration: --cc=/usr/local/gcc-4.4.4/bin/gcc
libavutil 50.23. 0 / 50.23. 0
libavcore 0. 0. 0 / 0. 0. 0
libavcodec 52.84. 0 / 52.84. 0
libavformat 52.77. 0 / 52.77. 0
libavdevice 52. 2. 0 / 52. 2. 0
libavfilter 1.26. 1 / 1.26. 1
libswscale 0.11. 0 / 0.11. 0
[alsa @ 0x11d6470] Estimating duration from bitrate, this may be inaccurate
Input #0, alsa, from 'hw:2':
Duration: N/A, start: 18534.705712, bitrate: N/A
Stream #0.0: Audio: pcm_s16le, 32000 Hz, 2 channels, s16, 1024 kb/s
[video4linux2 @ 0x11e7b40] Estimating duration from bitrate, this may be
inaccurate
Input #1, video4linux2, from '/dev/video0':
Duration: N/A, start: 1280233690.738718, bitrate: -2147483 kb/s
Stream #1.0: Video: rawvideo, yuv420p, 768x576, -2147483 kb/s, 1000k tbr,
1000k tbn, 1000k tbc
File 'test.avi' already exists. Overwrite ? [y/N] y
[buffer @ 0x11f3200] w:768 h:576 pixfmt:yuv420p
Output #0, avi, to 'test.avi':
Metadata:
ISFT : Lavf52.77.0
Stream #0.0: Video: mpeg4, yuv420p, 768x576, q=2-31, 200 kb/s, 25 tbn, 25
tbc
Stream #0.1: Audio: mp2, 32000 Hz, 2 channels, s16, 64 kb/s
Stream mapping:
Stream #1.0 -> #0.0
Stream #0.0 -> #0.1
Press [q] to stop encoding
[alsa @ 0x11d6470] ALSA buffer xrun.
frame= 688 fps= 26 q=31.0 Lsize= 2189kB time=27.68 bitrate= 647.8kbits/s
video:1922kB audio:216kB global headers:0kB muxing overhead 2.384571%
----------
status: new -> open
substatus: new -> reproduced
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FFmpeg issue tracker <[email protected]>
<https://roundup.ffmpeg.org/issue1249>
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