I had forgotten to test with shared libs and it turns out jack and alsa
were directly accessing symbols in the renderer (and in jack's case,
linking in a duplicate of the renderer).
Fixes#16.
Output plugins can use either a push model (synchronous) or a pull
model (asynchronous). The ALSA plugin now uses the pull model. This
paves the way for making jack output a simple output plugin rather than
the combined render/output plugin it currently is (for #16) as now
snd_dma works with both models.
This gets the alsa target working nicely for mmapped outout. I'm not
certain, but I think it will even deal with NPOT buffer sizes (I copied
the code from libasound's sample pcm.c, thus the uncertainty).
Non-mmapped output isn't supported yet, but the alsa target now works
nicely for pull rendering.
However, some work still needs to be done for recovery failure: either
disable the sound system, or restart the driver entirely (preferable).
This brings the alsa driver in line with the jack render (progress
towards #16), but breaks most of the other drivers (for now: one step at
a time). The idea is that once the pull model is working for at least
one other target, the jack renderer can become just another target like
it should have been in the first place (but I needed to get the pull
model working first, then forgot about it).
Correct state checking is not done yet, but testsound does produce what
seems to be fairly good sound when it starts up correctly (part of the
state checking (or lack thereof), I imagine).
and rename the variable since it's not the size of the frame (may be
from the very early days of ALSA development, and I suspect the
terminology changed a bit).
The calculation was including the bits per sample, which makes no sense
as the period size determines the number of samples in a submission
chunk (and thus latency). For now, set it to around 5.5ms (will probably
need a cvar).
I added Sys_RegisterShutdown years ago and never really did anything
with it: now any system that needs to be shutdown can ensure it gets
shutdown on program exit, and in the correct order (ie, reverse to init
order).
If the default sound device does not support mmap access, retry with
plughw. However, assume the user knows best and do not retry if snd_device
has been set to anything, including "default".
QF alsa support now works out of the box with pulseaudio.
Due to quake's original sound engine using a push model, the actual place
to which the sound data should be written is not necessarily where the
"hardware" dma cursor is, but rather where the last write finished off.
Thus, the correct output location is indicated by snd_paintedtime rather
than snd_shm->framepos.
Unfortuanately, I can't test this properly as I don't have any such
hardware, but as the code is mosly an edited copy of the interleaved code,
any errors should be easy to fix.
