sound driver for RTAI

Jan Kiszka kiszka at rts.uni-hannover.de
Fri Jul 29 10:08:16 CEST 2005


Paolo Mantegazza wrote:
> Thomas Witzel wrote:
> 
>>
>> I'm very interested in this topic and started working on an Audigy 
>> driver derived from the ALSA code base. I didn't have too much time 
>> for this yet.
>> I was thinking of using fusion. Whats the reason to prefer magma ?
>>
> 
> Recall: we are talking of direct within the acustic band processing!!!
> 
> - Machine: dual PIII, 1GHz, ADEOS r12 (as available within magma, not 
> the official one) for Linux-2.6.12.
> 

Adeos for 2.6.12 seems to be broken (we are already getting lock-ups on 
insmod rtai_hal). Did you also try on 2.6.11 or older kernels as well?

> - Load: X opened, "ping -f -s1500 somewhere", "dd if=/dev/hdb2 
> of=/dev/null bs=1M count=1000".
> 
> + Native fusion latency.c run at 50 Khz:
> 
> == Sampling period: 20 us
> RTT|  00:00:01
> RTH|-----lat min|-----lat avg|-----lat max|-overrun|----lat best|---lat 
> worst
> RTD|        4200|        5728|       24315|      20|        4200| 24315
> RTD|        4340|        5830|       47553|      54|        4200| 47553
> RTD|        4036|        5737|       43138|      81|        4036| 47553
> RTD|        2130|        7257|       42522|     364|        2130| 47553
> RTD|        2333|        5838|      236254|     410|        2130| 236254
> RTD|        4402|        5778|       42390|     423|        2130| 236254
> ---|------------|------------|------------|--------|------------------------- 
> 
> RTS|        2130|        6028|      236254|     423| 00:00:07/00:00:07 
> (i.e. a 7 second run)

This is likely a bug, not a design problem. The latencies we measured 
even on smaller systems (Pentium I 133 MHz) over longer periods are not 
that extrem, a bit higher than classic (due to the strictly layered 
design of fusion), but acceptable for common applications. The latency 
numbers I recall for a Pentium M, 1,3 GHz: < 20 us. Not tested with 
latest fusion and kernel release, but rather constant over the last 
versions.

Jan




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