title: How can I capture audio AND video simultenaous with ffmpeg from a linux USB capture device
body: <p>I'm capturing a video by means of an USB Terratec Grabster AV350 (which is based on the em2860 chip).</p>
  
  <p>I don't succeed to get the audio when it is played . If I play the captured video with vlc or with ffplay I got only 3 seconds sound and then a silence for the rest of the video ...</p>
  
  <p>During the capturing I don't get any errors. At the end it indicates the size of the video and audio captured ....</p>
  
  <p>I'm using the ffmpeg command for this :</p>
  
  <p><em>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</em></p>
  
  <p>The log is :</p>
  
  <pre><code>[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 -&gt; #0.0
  Stream #0.0 -&gt; #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%
  </code></pre>
  
  <p>If I reduce the command for only capturing audio, then the audio file can be played successfully :</p>
  
  <p><em>ffmpeg -f alsa -ac 2 -i hw:3,0 -acodec ac3 -ab 128k test5.avi</em></p>
  
  <pre><code>[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 -&gt; #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%
  </code></pre>
  
  <p>If I run the command for only video capturing then vlc or ffplay can play the video successfully :</p>
  
  <p><em>ffmpeg -f video4linux2 -i /dev/video0 -vcodec mpeg4 -b 12000k -r 25 test5.avi</em></p>
  
  <pre><code>[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 -&gt; #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%
  </code></pre>
  
  <p>Strange behaviour I noticed is that when I tried capturing video and audio, I can not capture the audio afterwards any more,
  unless I unplug the AV350 first.</p>
  
  <p>The G350 is located at card 3 :</p>
  
  <pre><code>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
  </code></pre>
  
  <p>The OS is a Linux 2.6.38-8-generic with the Ubuntu Natty Narwhal version</p>
  
  <p>Any help on how to tackle this issue would be great ....</p>
  
  <p>Thanks ! </p>