18 Sep
2005
18 Sep
'05
7:01 p.m.
Flo, Thanks for the jack suggestion. I definetly do need to spend some
time working with jack on my system. Also, thanks for the great low
latency documentation on tapas - ugh!. After getting 2.6 setup with |
Preemptible Kernel (Low-Latency Desktop), fiddeling with my hardware to
get the soundcard irq's right, and some tweeking with chrt all I can say
is "wow. WOW!".
I don't think there is anything you can do on a 2.4 kernel to get close
to this level of performance and control. Sweet! I almost giggle as the
entire system temporarily hangs while linuxsampler loads gig files at
outrageous speed. Also, I wanted to let you know that after a bit more
hacking I was able to get dshare working with the ice1712. It's awesome.
I can send linuxsampler out of channels 1-4 and have fluidsynth playing
out of channels 5 & 6, with 2 channels to spare for ecasound or
something... all simultaneously, at very low latency, & hardly any
processor load. I paid for the hardware... might as well take advantage
of it. Besides, this way I can give my processor a break, under-clock
it, & keep fan volume very low. Here is a snippet from asound.conf. -Garett
|pcm_slave.66_slave {
pcm "hw:1,0"
channels 8
rate 44100
buffer_size 256
period_size 128
}
pcm.66ch1234_dshare {
type dshare
ipc_key 18273645
slave 66_slave
bindings.0 0
bindings.1 1
bindings.2 2
gindings.3 3
}
pcm.66ch1234 {
type plug
slave.pcm "66ch1234_dshare"
}
pcm.66ch56_dshare {
type dshare
ipc_key 18273645
slave 66_slave
bindings.0 4
bindings.1 5
}
pcm.66ch56
type plug
slave.pcm "66ch56_dshare"
}
Florian Schmidt wrote:
On Thu, 15 Sep 2005 22:40:32 -0600
Garett Shulman <shulmang(a)colorado.edu> wrote:
Hello, I have been fooling around with my alsa
asound.conf in an attempt
to take advantage of the hardware mixer in my ice1712 and have multiple
apps output to it.
The hw mixer on the ice1712 is not doing what one normally refers to as
hardware mixing with consumer grade cards (i.e. allowing several apps
concurrent access at the same time). It mixes and routes channels from
its single 10 in/12 out channel device.
The way to get concurrent access with an ice1712 based card is _software
mixing_. That is, ALSA needs to do it (or whatever sounddriver you use).
I would urge you to take a very long look at JACK though. LinuxSampler
has excellent jack support and most apps made for peolpe creating music
usually have jack support, too. You'll save yourself lots of hassles
(setting up jackd isn't so tough when you read some docs). It is very
simple to route specific LS patches to specific output channels on your
ice based card when using jack.
In order to acomplish this I need linuxsampler to
be
able to access devices I setup in asound.conf instead of just hw:x,x
devices. This was easy enough to acomplish by nuking all of the '"hw:"
+' code from AudioOutputDeviceAlsa.cpp. The next issue relates to the
fact that the alsa dshare plugin requires that all of the "virtual
devices" that I create from the ice1712 card share the same buffer_size,
period_size, periods, & period_time settings. So, linuxsampler crashes
when it tries to set buffersize and periods. I figured I would just find
out what linuxsampler was trying to use for those values, setup the same
values in the asound.conf and then comment the code that sets them in
linuxsampler. This seems to work except that when linuxsampler connects
to the device I notice click and pops from the device & the output from
linuxsampler is rather distorted. I suspect that I'm just not setting
the values quite right in asound.conf. However, I guess I also may be
just mangleing linuxsampler beyond proper function. :) I was wondering
if anywone has any suggestions. When linuxsampler tries to set the
buffersize it is using FragmentSize=128 and Fragments=2. So I am
interpreting this as period_size=128, periods=2, & buffer_size=256. The
slave device in asound.conf looks like this:
pcm_slave.66_slave {
pcm "hw:0,0'
channels 8
rate 48000
buffer_size 256
period_size 128
periods 2 #I also tried 1 here... counting from 0...
period_time 0
}
Then I create some dshare devices from this and some plug devices for
each dshare device and connect linuxsampler to one of the plug devices.
Any suggestions would be greatly appreciated. -Garett
dshare still won't allow you to have multiple apps use your ice1712
card. You'll need dmix for that. Have a look at alsa.opensrc.org if you
want to go this route. dmix will probably kill latency though.
But better take a look at jackit.sf.net.
Regards,
Flo