Hi all.
I have a problem during 10 channel, full-duplex IO using ALSA 0.9-beta6 and a Midimann
Delta 1010. (Linux 2.4.7-low-latency, AMD Athlon 600Mhz, 256MB RAM)
I use my own program (which BTW will be releases in a .01v in some weeks) which does
this (+some other bits +the same for capture - C++ methos from my ALSA-wrapper ...):
Open (cname, SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK)
SetAccess (SND_PCM_ACCESS_RW_INTERLEAVED)
SetFormat (SND_PCM_FORMAT_S16_LE)
SetBufferTimeNear (400000)
SetPeriodTimeNear (400000 / 4)
Using the plug layer I get this setup:
min_ch: 10
max_ch: 10
min_rate: 44100
max_rate: 44100
period_size: 2730
buffer_size: 6553
periods: 2
Then I use normal ReadI / WriteI to pass the data to ALSA.
I works pretty well, except after 20-30 seconds I get many XRuns every 1 - 2 seconds.
They happen everytime Linux decides to flush the data in the disc-cache. (I have a IBM
30gig IDE disk (yes in UDMA66 mode ...) with an ReiserFS on it.)
To check if this guess was right I used my NFS mounted Server (100MBit, K6-2 200, 32MB
Ram, slower IDE drives ...) to store the data - and I nearly never got XRUns (even
having a laptop logged in, GNOME 2x, Konqui 2x, XEmacs 2x and a GCC compiling) ... .
Also this hack reduces the XRUNs to zero:
while true; do echo "syncing ..."; sync; sleep 1; done
So: Has someone some advices what to do better (or even to set via sysctl) ...
I know that using hw:0 and SND_PCM_FORMAT_S32_LE would same some converting time ... .
Are there some tipps using ALSA and or multi-channles cards better ?? (MMap wouldn't
save much here, would it??)
And another question to ALSA:
Would it be possible to return better values for:
snd_pcm_hw_params_get_channels_min / max
snd_pcm_hw_params_get_rate_min / max
when the plug layer is used?:
min_ch: 1
max_ch: 1073741823
min_rate: 1
max_rate: -1
This way the users has to enter how many channels he want's to have. And I have no
possibility to check the count or provide meaningfull defaults or selectable ranges
for the card ... - and using the hw:x directly I have to provide all format
convertions myself ...
Thanks a lot
Ren�
--
Ren� Rebe (Registered Linux user: #127875)
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