[PD-dev] jack dbus?

[katja]

On Wed, Jun 5, 2013 at 2:16 PM, Roman Haefeli <reduzent at 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