On Mon, Apr 18, 2011 at 05:21:46PM -0400, Paul Davis wrote: > On Mon, Apr 18, 2011 at 4:52 PM, S. Massy <lists@xxxxxxxxxxxx> wrote: > > Thanks, > > Builds and runs fine on Debian Wheezy AMD64. What latency would be > > considered average? What numbers should one expect? > > the "excess" value is generally on the order of several tens of > samples in each direction. it can reach as high as the low hundreds. > with USB audio (and potentially some firewire devices, the excess can > even get up into the thousands, but its dependent on a variety of > factors. this assumes you are doing the obvious thing and measuring a > loopback via a D/A and A/D converter pair. > > for reference, my RME HDSP system, connected to a Frontier Designs > Tango24 converter, meaures 68 samples of total excess latency, so > about 34 in each direction. That's a very typical value. If you have an HDSP or any other card with ADAT (or MADI) interfaces it can be interesting to measure the excess latency with a digital loopback as well. If this is much less than the value obtained when going through the DA/AD converters, then the difference is an indication of the type and lenght of the anti-aliasing filters used in the converters. If these filters are linear-phase (i.e. a symmetric FIR), then each of them will add a delay equal to half the length of the filter, so the excess delay is a measure of the filter length. Values I've seen so far appear to be much less than e.g. the filter lengths used by libsrc or zita-resampler at high quality settings. Ciao, -- FA _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
