[MEncoder-users] cat /dev/video0 | mencoder - ...

[Bob Tennent]

 >|You could try -tv noaudio (or read the manual to find the correct
 >|incantation to
 >|record audio, for me - using btaudio - it's -tv alsa=1:adevice=hw.2).

  -tv noaudio

produces 

  v4l2: ioctl request buffers failed: Invalid argument
  v4l2: 0 frames successfully processed, 0 frames dropped.
  ============ Sorry, this file format is not recognized/supported =============
  === If this file is an AVI, ASF or MPEG stream, please contact the author! ===
  Cannot open demuxer.

I don't understand why this is so complicated.  

   cat /dev/video0 > file.mpg

produces a perfectly good mpg that mencoder can process, even while it's
being created. Why isn't a simple buffer or pipe sufficient?  

Bob T.