On Wed, 2008-04-09 at 15:58 -0400, Dave Jones wrote: > On Wed, Apr 09, 2008 at 07:42:02PM +0200, Hans de Goede wrote: > > I believe this is easily feasible given enough manpower, most ccrma packages > > are pretty clean, they just need someone to push them through the review > > process, then the biggest hurdle left is ... the rt-kernel. > > > > Well since I seem to be talking to the right person now, I know you hate this > > question, but ... how strongly would you object to having an rt kernel variant > > within Fedora? > > Not incredibly keen tbh. I'd sooner just add -rt to the regular kernel package > and suck it up, but that obviously takes us further from our 'upstream first' > mantra. > > Ingo & Thomas are getting sizable chunks of it merged upstream, but I don't think > we'll be seeing it all merged soon, but then again, F10 is quite a ways off, > and with a few more kernel releases, who knows. > Depends how objectionable the remaining bits are I guess. > Given that so many people are now distributing products based on this work, getting > it all in mainline is obviously important, and there's no shortage of manpower > helping drive it there. > > All this said, I personally haven't hit any issues with things like MIDI in > Fedora where the -rt kernel would have helped me. Maybe my gear is special, > but latency between me hitting a key on a synth and having that note show > up in rosegarden, and a sound being created is well below perceivable. And that would be how many milliseconds? Can you run with 3 to 5 milliseconds latency without xruns on a loaded system with the stock kernel? With the right hardware the answer is probably yes, most of the time. The problem is the small percentage of frames where you _do_ get an xrun and the click that goes with it. It could be nobody notices it, it could be it actually ruins the concert or recording session. What could seem below the perception level to you (caveat: I don't know if you are a musician and what instrument you play) may bother a professional percussionist using the computer as an instrument. It all depends on your demands as a performer. > I'm interested to hear any test cases you guys may have that justify why > you need -rt. Besides realtime performance, all the audio-over-the-network being done at CCRMA needs it (see: http://ccrma.stanford.edu/groups/soundwire/). This is, in a nutshell, multichannel (between 4 and 8 channels) non-compressed high quality bidirectional audio being sent between 2 or 3 geographically separate locations to create a virtual concert hall and jam session or concert. You don't want to add _any_ latency to the one that speed of light already gives us :-) We routinely run at 64 frames (or 128 if the links are not good). The stock Fedora kernel is just not good enough although I'm sure it is getting better all the time. > Right now the guys working on that stuff typically have a > bunch of 'boring' test cases more tailored towards replicating situations > like stock trades and the like. If we can construct additional use-cases > I'm sure Ingo, Thomas & co would be very interested to hear about them. > Especially if these cases are triggering different latency paths. The apps being worked on at CCRMA (jacktrip) would touch both the network drivers and drivers for pro audio cards. Probably disk as well if the same host is being used to record the performance in Ardour. -- Fernando _______________________________________________ Fedora-music-list mailing list Fedora-music-list@xxxxxxxxxx http://www.redhat.com/mailman/listinfo/fedora-music-list
