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[Csnd] Problems with low buffer size and full duplex

Date2012-03-05 12:14
FromBernt Isak Wærstad
Subject[Csnd] Problems with low buffer size and full duplex
AttachmentsAudioThrough.csd  
I have made the easiest possible instrument to test buffer sizes with full duplex audio and the result is quite depressing. On my computer (MacBook Pro 3yrs old running 10.6.8 and Csound 5.16) I can't get audio through without dropouts with settings ksmps=16, -b32 and -B64. I've tested this with two different sound cards (RME Firfeface 800 (firewire800) and Motu UltraLitemk3 (USB)), but the result is the same. In Ableton Live I have no problem using 32 samples as buffer size and with Max/MSP I can use I/O Vector size 32 (equals -B I guess) and signal vector size 1 (equals ksmps I guess) without any trouble.

I've tested the same setup on Øyvinds Windows PC, the iMacs on our lab and a friends MacBook (newer than mine, 10.5.8 and Csound 5.12). Neither Øyvinds PC nor the iMacs had any trouble, but the other MacBook had the same problem (even worse actually).

I also found out that I had to go as high as 128 for -b before the dropouts stopped. -B didn't seem to matter? Having -b at 64 and -B at 1024 didn't produce the latency you'd expect from 1024 samples buffer size. If -B doesn't affect the latency, then what does it do? 

Any ideas of I might do wrong here?

The CSD (also attached):

<CsoundSynthesizer>
<CsOptions>
-iadc5 -odac4 -b32 -B64
</CsOptions>

<CsInstruments>

sr = 44100
nchnls = 1
ksmps = 16

instr 1

a1 inch 1

out a1
endin

</CsInstruments>

<CsScore>
i1 0 100
</CsScore>

</CsoundSynthesizer>

--
Mvh.

Bernt Isak Wærstad