[alsa-devel] Master vs. Front/Rear/LFE/... elements

Takashi Iwai tiwai at suse.de
Thu May 7 12:30:07 CEST 2009

At Thu, 7 May 2009 11:09:16 +0100,
Mark Brown wrote:
> On Thu, May 07, 2009 at 10:49:22AM +0200, Takashi Iwai wrote:
> > IMO, the best would be a total rewrite of the current mixer API, as I
> > mentioned some times.  Right now it's more complicated than needed,
> > but not powerful enough to handle exceptional cases.
> Indeed - for example, something that allowed audio routing to be
> expressed in the mixing API would be a very big win for embedded systems
> too.

Right.  But this would also require some changes in the driver side,
and it could be complicated.

Actually, we had this kind of information in the time of ALSA 0.5.
However, it ended up with too burden to the driver code because one
had to write a comprehensive static graph in the driver code itself
(generated by hand!).  Also, some mixer elements are tightly coupled
with certain audio components, but some are pretty abstract and hard
to put into a graph.  So, we reduced that in the newer API and
implemented a straight array of control elements instead.

Nevertheless, a sort of linking would be useful in addition to the
current form.  For example, coupling between the control element and
the PCM stream is missing, too.

Alternatively, we may have an external data outside the kernel
driver.  In that case, the data can be expressed more flexibly
(XML? Oh yeah :)


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