Hi,
first of all, hello, I'm a new to alsa development and was hoping I
could learn a thing or two here.
So here's the questions I have.
What's up with the documentation, specifically the API docs. It's ...
not easy figureing stuff out from the doxygen generated docs. Right now
I'm looking specifically at the:
void snd_mixer_selem_get_id (snd_mixer_elem_t *elem,
snd_mixer_selem_id_t *id)
Get mixer simple element identifier.
*Parameters:*
/elem/ Mixer simple element handle
/id/ returned mixer simple element identifier
unsigned int snd_mixer_selem_id_get_index(const snd_mixer_selem_id_t
*obj)
Get index part of a mixer simple element identifier.
*Parameters:*
/obj/ Mixer simple element identifier
*Returns:*
index part
For example. Would you know what these functions do?
I THINK (and thus the question) that snd_mixer_selem_get_id(); fills (so
why not snd_mixer_selem_id_fill()) the elem id based on the elem we have
(via snd_mixer_first_elem() for example) and then we can query the two
fields from the struct via snd_mixer_selem_id_get_index and
snd_mixer_selem_id_get_name.
But then I wonder, how is this linked to an elem? What's the point of
get id? Isn't this info in elem also? If I wanted to do some accounting,
I'd have to have a struct with the elem and the sid (pointers) in it and
than use the sid to identify the elem? Since there's also an
snd_mixer_selem_get_name()
call, what's the point in having 2 identical structures? I don't get it,
and the documentation doesn't help at all regarding to this.
Then my second question is the following: If I'd write an application,
that uses alsa to output audio (for simplicities sake, let's look at
xmms), would I be able to add a (software) mixer element for the audio
output and be able to control the volume? I'm wondering this since
there's all these snd_mixer_selem_id_copy()
for example calls. I don't think I as a user am able to copy kernel
contents, so what's the point of this function? If I can do this (why
doens't xmms use it, they do a software volume control it seems, e.g.
very delayed, or is this exactly what I'm asking) can I think of what is
being said about the new Vista volume control crap, except for they dump
it right in the windows mixer, whereas here it's a private mixer/control
to the app that created it (much cleaner I think).
Thanks,
Oliver
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