[alsa-devel] RFC: PCM extra attributes

Takashi Iwai tiwai at suse.de
Fri Jun 19 14:46:11 CEST 2009

At Fri, 19 Jun 2009 13:43:08 +0100,
James Courtier-Dutton wrote:
> 2009/6/19 Takashi Iwai <tiwai at suse.de>:
> >
> > The alsamixer view isn't the issue I'm concerned.
> > These spontaneous controls should be IFACE_PCM in the first place.
> > They shouldn't be IFACE_MIXER.  For example, IEC958 status bits can be
> > associated to a dedicated PCM substream.
> >
> Would an option could be to stream the IEC958 status bits with the PCM stream?
> I.e. As an extra channel of the PCM multichannel stream.

I don't buy it because the status bits don't need resend at each time.
And for compatibility reason, this is a huge gap.

If any, we have already IEC958 raw subframe support that embeds the
status bits...

> Another option could be to stream the gain control values with the PCM stream.
> I.e. Instead of attributes attached to the PCM, stream those
> attributes with the PCM stream.

Hrm how can it be done?  Could you elaborate?


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