On Fri, 23 Jan 2004, Torrey Hoffman wrote:
> On Fri, 2004-01-23 at 01:52, Clemens Ladisch wrote:
> > John W. Cocula wrote:
> > > $ ./speaker-test -Drear -c 2
> > >
> > > ALSA lib pcm.c:1812:(snd_pcm_open_conf) Invalid type for PCM rear definition
> > > (id: rear, value: cards.pcm.rear)
> > > Playback open error: Invalid argument
> >
> > You cannot access the rear channels seperately (at least not
> > directly). The ICH only supports 2-channel (front), 4-channel
> > (front+surround) and 6-channel (front+surr+center+lfe) output.
>
> This is interesting... If I understand you correctly, you mean that the
> digital PCM data for the 4 channels or 6 channels must all be
> interleaved together and sent through a single device, just like the
> left and right channels of a stereo channel?
>
> If this is correct, would it be possible to set up a plug-in layer which
> opens the ICH hardware in 6-channel mode, but then provides three
> virtual stereo devices to applications?
>
> The plugin would just interleave, or multiplex the digital pcm data
> together, and insert silent "0" samples on any channel which wasn't
> opened by an application.
>
> Diagram: (each letter represents a 16-bit PCM sample)
>
> pcm stereo 1: ababab... --> |========| |hardware|
> pcm stereo 2: cdcdcd... --> | plugin |-->abcdefabcdef... -->|in 6 ch |
> pcm stereo 3: efefef... --> |========| | mode |
>
> My goal is to get my ICH-->realtech working in 6 channel output mode in
> a way that I can run three instances of Rhythmbox, streaming three
> totally independent stereo streams to three stereo amplifiers hooked to
> speakers in three different rooms :-)
>
> Hopefully this is not impossible?
No, use the dshare plugin with different channel bindings.
Jaroslav
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
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