>> the hammerfall cannot do this. the hammerfall-DSP can do matrix
>> routing of signals between channels, but it does not mix software
>> streams down to a channel.
>
>Crap! :-) So does this mean that RME card cannot be accessed from
>multiple applications at the same time? This is one of the most annoying
>limitations Linux audio architecture has had ever! It automatically
>eliminates any kind of real-time multi-channel performance capability
>where one wants to utilize multiple processes (i.e. pd, jmax and cmix
>running at the same time). Even the old SGI's had this solved in a very
>elegant fashion, needless to mention OS X or Windows (yes, I know, I
>know, at the expense of latency, but at least I was not limited to using
>one app at the time)...
whoa! easy! relax!:)
1) nobody said it couldn't be accessed from multiple applications at
the same time. you asked if the hardware could do it. i gave you
the answer to that question, and the answer is "no". that doesn't
mean that multiple applications can't access it simultaneously.
2) it does mean, however, that some part of the software involved in
audio i/o has to be a lot more complex. ALSA follows kernel design
in that it does not put policy or data formatting into kernel code
(to contrast with Windows, for example, which includes a mixer that
runs in kernel mode). Instead, ALSA does this sort of code in user
space (in alsa-lib), which makes for a more stable but also
somewhat more complex set of code.
3) this is accomplished by using the "share" PCM device type. i have
no experience with this on *any* ALSA card - i hope that abramo
and/or others who have tried it out can explain how to configure
it in ~/.asoundrc and how well it works these days.
4) yes, latency is not so good with this system and the different
apps do not necessarily stay in sync with each other.
5) i suggest you read
http://jackit.sourceforge.net/docs/design/
to understand my and several other people's) proposal for how to
deal with this issue in what we consider to be the correct way.
>Do you know whether this software mixing stuff done in SBLive soundcard
>is done in hardware or in software that the creative has released?
hardware. most consumer cards these days do this, and they typically
offer quite a lot of "subchannels" (eg. 32).
>Is there a way for artsd to be aware of the multiple channels RME card
>has and for artsd to provide software downmixing despite the fact RME
>has no mixer?
artsd can do this, as can esd. whether you wish to use those solutions
will depend a great deal on what you're trying to do. a real time (low
latency) FX box, for example, cannot use them - they are too slow and
they do not ensure sample accurate sync.
--p
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