如何从linux USB捕获设备捕获与ffmpeg同步的音频和视频

播放时我没有成功获取音频.如果我使用vlc或ffplay播放捕获的视频,我只有3秒钟的声音,然后对视频的其余部分保持沉默……

在捕获过程中,我没有收到任何错误.最后它表明了录制的视频和音频的大小….

我正在使用ffmpeg命令：

ffmpeg -f alsa -ac 2 -i hw：3 -f video4linux2 -i / dev / video0 -acodec ac3 -ab 128k -vcodec mpeg4 -b 6000k -r 25 test5.avi

日志是：

[alsa @ 0x9bcd420]Estimating duration from bitrate,this may be inaccurate
Input #0,alsa,from 'hw:3':
Duration: N/A,start: 69930.998994,bitrate: N/A
Stream #0.0: Audio: pcm_s16le,44100 Hz,2 channels,s16,1411 kb/s
[video4linux2 @ 0x9bf5d30]Estimating duration from bitrate,this may be inaccurate
Input #1,video4linux2,from '/dev/video0':
Duration: N/A,start: 1307111377.654173,bitrate: -2147483 kb/s
Stream #1.0: Video: rawvideo,yuyv422,720x576,-2147483 kb/s,1000k tbr,1000k tbn,1000k tbc
[ac3 @ 0x9bf9590]No channel layout specified. The encoder will guess the layout,but it might be incorrect.
Output #0,avi,to 'test5.avi':
Metadata:
ISFT : Lavf52.64.2
Stream #0.0: Video: mpeg4,yuv420p,q=2-31,6000 kb/s,25 tbn,25 tbc
Stream #0.1: Audio: ac3,stereo,128 kb/s
Stream mapping:
Stream #1.0 -> #0.0
Stream #0.0 -> #0.1
Press [q] to stop encoding
frame= 1283 fps= 25 q=2.3 Lsize= 38677kB time=51.32 bitrate=6173.9kbits/s
**video:37755kB audio:846kB** global headers:0kB muxing overhead 0.198922%

如果我减少仅捕获音频的命令,则可以成功播放音频文件：

ffmpeg -f alsa -ac 2 -i hw：3,0 -acodec ac3 -ab 128k test5.avi

[alsa @ 0x8ede420]Estimating duration from bitrate,from 'hw:3,0':
Duration: N/A,start: 70395.998935,1411 kb/s
[ac3 @ 0x8eebac0]No channel layout specified. The encoder will guess the layout,to 'test5.avi':
Metadata:
ISFT : Lavf52.64.2
Stream #0.0: Audio: ac3,128 kb/s
Stream mapping:
Stream #0.0 -> #0.0
Press [q] to stop encoding
size= 227kB time=13.62 bitrate= 136.8kbits/s
**video:0kB audio:213kB** global headers:0kB muxing overhead 6.902375%

如果我只运行命令进行视频捕获,那么vlc或ffplay可以成功播放视频：

ffmpeg -f video4linux2 -i / dev / video0 -vcodec mpeg4 -b 12000k -r 25 test5.avi

[video4linux2 @ 0x91d6420]Estimating duration from bitrate,start: 1307112044.025687,bitrate: -2147483 kb/s
Stream #0.0: Video: rawvideo,1000k tbc
Output #0,12000 kb/s,25 tbc
Stream mapping:
Stream #0.0 -> #0.0
Press [q] to stop encoding
frame= 388 fps= 25 q=2.0 Lsize= 12963kB time=15.52 bitrate=6842.5kbits/s
**video:12949kB audio:0kB** global headers:0kB muxing overhead 0.114584%

我注意到的奇怪行为是,当我尝试捕获视频和音频时,我无法再捕获音频了,
除非我先拔下AV350.

G350位于卡3：

htpc@htpc-01:/proc/asound/G350/pcm0c$more info
card: 3
device: 0
subdevice: 0
stream: CAPTURE
id: USB Audio
name: USB Audio
subname: subdevice #0
class: 0
subclass: 0
subdevices_count: 1
subdevices_avail: 1

操作系统是Linux 2.6.38-8-Ubuntu Natty Narwhal版本

任何有关如何解决这个问题的帮助都会很棒….

谢谢 ！