Robert Jonsson wrote: [snip] > The difference between the two is that timidity probably opens the soundcard > with write-only, whereas jack by default opens it read-write (full duplex). > The emu10k driver doesn't allow any setting below -p 512 if you run in full > duplex. If you change the output of jack so it only writes you could set it > lower here too. You are right! Forcing jack to open alsa in plaback only mode I can set a period 256 frames with 2 periods of buffer. I play via midi so I don't need the capture the most of times. So playng with ZynAddSubFX I can get a latency of 10 ms! This isn't just a "pretty low latency" but a _very_ low latency for me :-). Thanks. > I think this is a shortcoming of the driver. I've come to understand that the > emu10k1 is capable of much lower settings with the kx drivers in windows. But it's a sad closed (I think almost) personal project. Personally I apprecciate a lot those ideas about drivers policy: http://www.gnu.org/brave-gnu-world/issue-51.en.html don't you? [snip] > Very few cards/drivers support using only one buffer. If I understand things > correctly it means that whenever the buffer runs empty the program has to > rewrite the buffer _before_ the soundcard needs another single sample. Which > is a _very_ short time. > In practice this setup is unusable. ok, I understand [snip] >>The last but not least, I have a general question about jack: if I a >>stream pass twice or more times into jack (for example alsa in -> jack >>rack -> ardour -> alsa out, 3 times) does the latency increases twice or >>more, proportionally, or it is only related to the various apps latency? > > > Somebody more knowledgeable than me should answer that :) I've done the question because I noticed that jamin increase the latency much more then other apps (like ardour or jack-rack). For example the with the setup: midi -> ZynAddSubFX -> jack-rack -> ardour -> alsa out (5.3 ms) I have no (at least easily) audible delay when I play (using 2 periods of 512 frames), while with: midi -> ZynAddSubFX -> jamin -> alsa out I have a strong delay of (I estimate) about 0.1 ~ 0.2 secs, which means no realtime response. So I understand that I don't understand something about how jack works :-) Anyway, there is a way to mesure the global in-out latency? (I've tried the Benno's latency test, it does the benchmark but does not produce any png result, and I think is only a kernel-related test) [snip] > Not stupid at all. I hope my answers where correct and satisfactory. Fully satisfactory, you fullfilled all (well quite all ;) my doubts in one time! Thanks a lot. > /Robert Antonio
