On Wed, Jun 5, 2013 at 2:16 PM, Roman Haefeli <reduz...@gmail.com> wrote:
[...] >> Right. I would propose the following measurement protocol: >> >> (setup/usecase A: Pd only through ALSA) >> 1. In Pd using ALSA backend, run sine test signal in 'Media > Test >> Audio and Midi...' >> 2. Set Pd's buffer to lowest possible value such that there are no I/O >> error messages or audible dropouts during 'normal Pd use', that is, >> while clicking (radio)buttons or switching between already loaded Pd >> windows. >> 3. For this nominal latency setting, measure actual roundtrip latency >> via line loopback or speaker / mic loopback, using patch >> latency-tester2.pd which was attached to my May 29 post in this >> thread. >> >> (setup/usecase B: Pd and PulseAudio through JACK/ALSA) >> 4. Set up a routing with Pd and PulseAudio as JACK clients. >> 5. In Pd, run the sine test signal. Simultaneously, play this video in >> a browser while routing it's sound through PulseAudio / JACK: >> http://www.youtube.com/watch?v=_63Cc6vPFVI&feature=youtu.be >> 6. For this combination, get the lowest nominal latency in Jack such >> that there are no I/O errors in Pd, or audible dropouts in either >> audio signal. JACK must be restarted for a new buffer setting to take >> effect. This is the most time-consuming aspect of the measurement. >> 7. For this routing and settings, measure the actual roundtrip latency >> through Pd. >> >> 8. Report nominal + measured latencies for setup A and B, together >> with relevant hardware and system info. >> >> My results for Panasonic CF-19 1 GHz Core2Duo, Xubuntu 12.04, built-in >> soundcard, no preemptive kernel: >> - setup/usecase A: 15 ms buffer in Pd, 18 ms measured roundtrip latency >> - setup/usecase B: 15 ms buffer in Pd, 23.2 ms (2*512 samples) buffer >> in JACK, 49.3 ms measured rountrip latency through Pd > > > My results forIntel Core 2 Duo T8300 2.4GHz, Ubuntu 12.04 i386 > (3.2.0-44-lowlatency-pae) > > HDA Intel > --------- > - usecase A: blocksize 128 in Pd, measured roundtrip 10ms > - usecase B: 5.9ms (2frames, 128fr/period), measured roundtrip 14.9ms > > > HDSP RPM with cardbus > --------------------- > - usecase A: blocksize 128 in Pd, measured roundtrip 10ms > - usecase B: 5.9ms (2frames, 128fr/period), measured roundtrip 14.9ms > > > Some notes: > Whether pulse server was connected to jackd didn't have any influence at > all on the best working jackd settings. Either I could start jackd or > not. When jackd was running, I didn't get any drop-outs, with or without > pulse connected as client. Just to make sure: did you also play the internet video, and get uncompromised quality for both audio signals with those settings? > The buffer(ms) setting in Pd doesn't have any > influence on the effective latency on my box, with both cards. That is > why I reported only the blocksize, which seems the only parameter to > have any effect on latency. With Pd connected to jackd, even blocksize > doesn't change anything. This is weird, eh? I guess the Media > Audio Settings > Delay(msec) sets Pd's buffer size (rounded or truncated to an integer number of blocks), when it's using ALSA. Anyway this setting normally influences measured latency in a linear fashion. When Pd goes through JACK instead, it seems that Pd's buffer size setting is irrelevant because JACK's buffer is forwarded to Pd. > Unfortunately, my expensive soundcard does not perform any better than > the built-in, regarding latency. It seems this is a regression in the > alsa from my Ubuntu version. I remember I was able to set a lower value > for frames/period, 32 and 64 have been also working in previous versions > of Ubuntu, with the same laptop and the same HDSP card. > > Nice latency measurement patch, btw. There is one smallish issue with > it. When testing low latency setups, the latency patch itself causes > drop-outs because of the 1-10000 loop executed in zero logical time. That is not elegant indeed, even though the loop comes after the data is recorded. I could not find an alternative for the loop, using vanilla objects. If it could be broken in parts, your [nbuntil] solution could help. Katja _______________________________________________ Pd-dev mailing list Pd-dev@iem.at http://lists.puredata.info/listinfo/pd-dev
