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我通過USB Terratec Grabster AV350（基於em2860芯片）捕獲視頻。如何從USB捕獲設備捕獲與ffmpeg同步的音頻和視頻
播放時我沒有成功獲取音頻。如果我用vlc或ffplay播放捕捉的視頻，我只有3秒的聲音，然後爲視頻的其餘部分保持沉默...
在捕獲期間，我不會收到任何錯誤。在結束它指示視頻和捕獲的音頻的大小....
我使用此ffmpeg的命令：
ffmpeg的-f ALSA -ac 2 -i HW：3 -f video4linux2 -i的/ dev/video0的-acodec AC3 -AB 128K -vcodec MPEG4 -b 6000K -r 25 test5.avi
日誌是：
[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, 720x576, q=2-31, 6000 kb/s, 25 tbn, 25 tbc
Stream #0.1: Audio: ac3, 44100 Hz, stereo, s16, 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%
如果我減少了命令只捕獲音頻，那麼音頻文件可以成功播放：
ffmpeg的-f ALSA -ac 2 -i HW：3,0 -acodec AC3 -ab 128K test5.avi
[alsa @ 0x8ede420]Estimating duration from bitrate, this may be inaccurate
Input #0, alsa, from 'hw:3,0':
Duration: N/A, start: 70395.998935, bitrate: N/A
Stream #0.0: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s
[ac3 @ 0x8eebac0]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: Audio: ac3, 44100 Hz, stereo, s16, 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%
如果我運行僅視頻，然後捕捉命令VLC或ffplay可以成功地播放視頻：
的ffmpeg -f video4linux2 -i的/ dev/video0的-vcodec MPEG4 -b 12000K -r 25 test5.avi
[video4linux2 @ 0x91d6420]Estimating duration from bitrate, this may be inaccurate
Input #0, video4linux2, from '/dev/video0':
Duration: N/A, start: 1307112044.025687, bitrate: -2147483 kb/s
Stream #0.0: Video: rawvideo, yuyv422, 720x576, -2147483 kb/s, 1000k tbr, 1000k tbn, 1000k tbc
Output #0, avi, to 'test5.avi':
Metadata:
ISFT : Lavf52.64.2
Stream #0.0: Video: mpeg4, yuv420p, 720x576, q=2-31, 12000 kb/s, 25 tbn, 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%
我注意到奇怪的行爲是，當我試圖捕捉視頻和音頻時，我不能再捕捉音頻， ，除非我先拔掉AV350。
G350是位於卡3：
[email protected]:/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
操作系統是Linux 2.6.38-8泛型與Ubuntu的納蒂獨角鯨版
就如何解決這個問題將任何幫助太棒了......
謝謝！
一些[正確的格式（http://stackoverflow.com/editing-help#code）將使這可讀。 – LordNeckbeard 2015-08-24 17:30:40