At Sat, 08 May 2004 20:32:04 +0200,
Ronald S. Bultje wrote:
> 
> Hi,
> 
> I'm working on properifying the ALSA support in GNOME Volume Control.
> When opening a sound mixer, I noticed that several elements will be both
> a capture and a playback element. Also, there is separate functions for
> setting the playback and the capture volume. How are those functions of
> the element related? If I set the playback volume, does this affect the
> capture volume on a hardware level? And what is the playback or capture
> part of this element supposed to visualize/abstractize?

the playback and the capture are independent.  they shouldn't affect
with eath other, and that's why there are different functions :)

basically, you should provide separated volume bars and toggle
switches for both playback and capture if two of them are provided.

> Also, I see several non-volume elements (switches? Things such as
> External Amplifier Power Down or 3D - switch). What are those? What do
> they do, what's their function, what do they visualize/abstractize on
> the hardware level?

each meaning depends strongly on the chip/driver.

> I'm asking all this to get an idea of how to picture those in GNOME
> Volume Control (for the first question: each function of the element as
> a separate track? Or all functions together as one track?; for the
> second question: as a checkbox? something else? omit completely?).

remember that the ALSA mixer interface doesn't provide the
well-abstracted mixer stuffs (yet).  they are almost as hardware
provides.  obviously we need another higher level abstraction.

IMO, there is no general design of the mixer, except for the very
basic elements like Master, PCM, etc.
look at Windows mixers - they all look differently.

hence, providing the mixer structure with an external db (e.g. via
XML) according to the driver/chip would be the best solution if you
write a "generic" mixer app.


Takashi


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