Subject: re: oss compatibility for >2 channels
To: None <>
From: matthew green <>
List: tech-misc
Date: 04/25/2007 11:25:59
   Hi -
   that's neither kern nor purely userlevel -- maybe that list
   is still good for something.
   PR pkg/35444 (mplayer bad timeout select and play.channels number for oss)
   reminds me of something: The NetBSD OSS emulation assumes that the number
   of play and record channels is the same. It seems common now that there is
   some 5.1 audio output but just a one or two channel input.
   The emulated SNDCTL_DSP_CHANNELS ioctl tries to set both play and record
   channels to the given number and fails if any of it fails. So there is no
   chance to enable more than two channels in that example.
   I'd suggest to treat play and record direction independently - see the
   appended patch. Is there anyone having deeper knowledge about OSS,
   or being able to test a real OSS with >2 channel hardware to judge
   whether such a change makes sense?

this patch doesn't quite work.  it does allow
"mplayer -channels 6 -ao oss" to not error out, but it does cause
the audio to play slow (maybe 3x?  it's hard to tell) and only in
two channels.

however, it's not clear to me that anyone has ever done >2 channels
with netbsd audio.  i can't seem to make it work with mplayer and
sun audio, but i haven't yet gotten to testing it more simply with
a plain 6 channel audio file and audioplay(1).