Hello ALSA-users!
Hello RT-users!
I think, this mail might be interesting for both the lists, since it's
dealing with ALSA and the usage of a realtime-kernel.
I've been playing around with ALSA for quite some weeks now and I am
trying to get reading of sound done with small latencies. Therefore I am
using the "hw:0:0"-device with SND_PCM_STREAM_CAPTURE and
SND_PCM_NONBLOCK. My device is configured with a total buffersize of 882
frames (44100Hz in SND_PCM_FORMAT_S16 on 2 channels).
All I do, is waiting 2 milliseconds and then reading with
snd_ocm_readi() as much as I can from the soundcard (well, I get the
amount of frames available after 2ms, of course. This timing is quite
stable).
I have the program running on an X86-board (500MHz Geode with
CS5535-Chipset), I applied the realtime patches of Ingo Molnar, I did
set my software to SCHED_FIFO and prio 90, the ICQ of the sounddevice is
set to 98 (this is done with chrt -f -p 98 `pidof "IRQ-11"`), my
/proc/interrupts is quite empty (see below) and I did set the latency of
the PCI-devices in order to give prio ty the soundcard:
setpci -v -s '*:*' latency_timer=20
setpci -v -d '1022:2093' latency_timer=80
My uname:
# uname -a
Linux master 2.6.29.5-rt22-486-voyage #1 PREEMPT RT Wed Jun 24 09:10:02
GMT 2009 i586 GNU/Linux
Here goes the /proc/interrupts - stuff:
#cat /proc/interrupts
CPU0
0: 1020847 XT-PIC-XT
timer
1: 2 XT-PIC-XT
i8042
2: 0 XT-PIC-XT
cascade
4: 982 XT-PIC-XT
serial
10: 762598 XT-PIC-XT
wifi0
11: 1788972 XT-PIC-XT CS5535
Audio
12: 4 XT-PIC-XT
i8042
14: 873 XT-PIC-XT
ide0
NMI: 0 Non-maskable
interrupts
LOC: 0 Local timer
interrupts
SPU: 0 Spurious
interrupts
CNT: 0 Performance counter
interrupts
ERR:
0
MIS: 0
My problem now: roundabout 5 times per minute, I get a buffer outrun,
which results in a "scratch" of the sound, that I am recording. It seems
like I am running over- and underruns again and again. The output looks
like this:
curdma=f3d8000 < f970000
bufaddr.
curdma=f3d8000 < f970000
bufaddr.
curdma=f3d8000 < f970000
bufaddr.
curdma=f3d8000 < f970000
bufaddr.
diff=dc8 >= dc8
buf_bytes.
diff=dc8 >= dc8
buf_bytes.
curdma=f3d8000 < f970000
bufaddr.
curdma=f3d8000 < f970000
bufaddr.
curdma=f3d8000 < f970000
bufaddr.
diff=dc8 >= dc8 buf_bytes.
(and so on...)
I found the driver module, that produces this output, it is
/usr/src/linux-2.6.29.5/sound/pci/cs5535audio/cs5535audio_pcm.c
>From line 329 and onwards, there is the function
static snd_pcm_uframes_t snd_cs5535audio_pcm_pointer
, which genreates this output and seems to be the reason for my crappy
sound.
Is there anyone among the RT-list or the ALSA-list who has a slight
idea, what my problem might be related to and how I can get rid of it?
Very kind regards,
Dennis Borgmann
------------------------------------------------------------------------------
_______________________________________________
Alsa-user mailing list
Alsa-user@xxxxxxxxxxxxxxxxxxxxx
https://lists.sourceforge.net/lists/listinfo/alsa-user
