[replying to pd-list]
Hi Simon
On Wed, 2016-10-12 at 09:30 +0200, Simon Iten wrote:
it would very much surprise me, if pd could do that in a generic way on all platforms. even daws or live struggle to do this *right* on different systems.
I'm not sure it's totally impossible. With jack, the latency is dependent on jackd's settings and I don't whether Pd has a change to know those. With ALSA, everything you need to know to calculate the latency Pd already knows.
why don't you patch a little tester app that sends some generated sounds, preferably with very clear attack, out and record this back in. that way you can measure the (roundtrip) latency of the whole system.
Of course, that is a way. "Knowing" the latency instead of "measuring" it would be so nice, though.
with a click track and a good musician that plays with it (that you record) you should be able to align generated sounds and live recorded material. this is how we do it in the studio if necessary :) but it is far from an automated process...
To make things at least a bit more feasible, I make the measured or calculated latency a configuration parameter, so that when you fire Pd up the next time with the same setup, the patch remembers the latency.
Roman
Am Sonntag, 9. Oktober 2016 schrieb Roman Haefeli :
Hi all,
I'm currently investigating audio latency compensation in Pd. The goal is for recorded audio to align well with generated sounds timing- wise. I'm wondering now what methods people already have employed in order to achieve that goal.
So far, I was able to find the formulas to calculate the correct latency when using ALSA and JACK audio back-ends as long as the paramaters 'Delay(msec)' and 'Block size' for ALSA, respectively 'Frames/period' and 'Periods/buffer' for JACK are known. Currently, this approach works, but requires me to tell the latency compensation calculator what driver I'm using and what the current settings are. Also, it yet only works on Linux, but not with any other drivers like CoreAudio, ASIO, etc.
How can I achieve correct latency compensation reliably on any platform? Is there some more generic way?
I'm also looking at IEM's mediasettings library, hoping it would deliver the required information to calculate latency. The README.txt says 'get/set Audio and MIDI settings within Pd', but I wasn't able to find a way to _get_ current settings other than 'advance 100', which probably refers to 'Delay(msec)' set to '100'. But still, if it would give all Pd audio settings, how would it know about current jackd settings?
Roman