FW (sorry) : [PD] Hammerfall : setting up latency for Pd

[julien.breval at tremplin-utc.net]

hi

> the measurements i have done with the HDSP/winXP have not been very 
> satisfying.
> the main problem used to be, that measurements tended to be 
> not-reproducable under winXP (as they were under linux)
> 
> test system was an athlon-XP3200+ machine (winXP-pro).

I seem to be luckier
I didn't make any objective measurements, but hearing it I get very good 
results

My PC is a Shuttle SB51 with P4 2.4GHz, and WinXP pro, and also Linux 
 
> as far as i remember i didn't use the "-blocksize" option (don't know 
> why; probably it had no effect)

I think this regards the pd internal vector size ; the smallest it is and the 
most performant it is (but more CPU too) ; default is 64 samples ... I put it 
to 128, it's stupid of course
I thought it corresponded to the sound card I/0 vector size (I should have 
used "-audiobuf" of course)

> the "-audiobuf" should be at least the corresponding value to the 
> buffer-size you set at the control-panel (for a buffersize of 128, use 
> 3ms of audiobuf)
> 
> 
> i didn't get any reasonable results with a buffer-size below 256.
> the best result i got was about 2179 samples (which is 50ms @ 44.1kHz)
> but it was not very stable (at least at at CPU-load of 80%)
> (but it really performed quite erratically: e.g: with an rme-buffer of 
> 2048 samples (which gave me a latency of 6019 samples) i didn't get 
> *any* good signal, even at a virtual load of 0% !!)
> 
> 
> that was the main reason, why we chose to use linux even more for 
> latency-critical applications. (at least we could do 835 samples latency 
>   with a load of 50% on the same machine with alsa/jack; and without 
> file-access (this does not mean writing to soundfiles, but rather saving 
> big-files at once) during dsp-processing the system gave us a stable 
> latency of 1603 samples at 80% cpu-load)

well, I prefer Linux too, but I have complex ALSA problems because my HDSP was 
too recent -- it should have been fixed now, and I will try to re-install 
Linux PlanetCCRMA ... in april (loads of work since september !)

> big tip:
> use your task-manager to prioritize the pd thread to "real-time" and the 
>    pdgui-thread (wish83) to "lowest".

will try this

thanks a lot for you advices

j