On 01 Apr 2003 22:57:28 -0500 Nick <nicktsocanos@xxxxxxxxxxx> wrote: > I am writing audio applications that are real-time. > I had been using Port Audio which is really very good, even without root > priviledges, it does a very good job. I want to support other sound > drivers, in case someone doesn't have Port Audio or can't get it to > work. > > I have just built my ALSA driver, it works ok, but I am getting terrible > latency problems and buffer underruns. The thing is it is a real-time > application, it must get audio to the card as soon as possible. Why is > it that OSS with Port Audio works so well, and my ALSA setup is > suffering? > > Is there something I need to do to ALSA to get near real-time > performance from it? I have heard people mention patching their kernel > for low latency. I have Jack but I have not started working with it yet. > Should I dump ALSA and just go for Jack? Is there something I need to do > to my kernel to get better performance? I would get Planet CCRMA if it > supported my OS, but it doesn't, so I have to tweak my box manually. High Nick ! At the moment there are two different approaches for low-latency in the linux-kernel. The first is from Ingo Molnar; it's quite simple but efficient (conditional scheduling at critical places). You can get it at http://people.redhat.com/mingo/lowlatency-patches/lowlatency-2.4.0-test7-A0 The second is made by Robert Love, it makes real heavy Changes in the Kernel which have a noticeable negative impact on overall System-througput, but the results are quite amazing ! The Patch is integrated int the 2.5-Kernel (CONFIG_PREEMPT), patches for 2.4 are available at ftp://ftp.kernel.org/pub/linux/kernel/people/rml/preempt-kernel/v2.4/ I use Robert's patch with the 2.5-Kernel since half a year without Problems; The interactive response of the Sytem under high loads is now MUCH better. Lacking real real-time Software i don't know if it helps there too. If the low-latency patches for the Kernel don't cure your Problem, consider testing a new 2.5.6x-Kernel; the scheduler was really improved in the last months ...
