Messages in this thread | | | From | est@hyperrea ... | Subject | Re: real-time threaded IO with low latency (audio) | Date | Sun, 18 Jul 1999 16:47:02 -0700 (PDT) |
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Benno Senoner <sbenno@gardena.net> discourseth: > David Olofson is developing an audio driver system for Linux > which uses RT-Linux and an API which will fit well into the actual > sound driver API. The goal will be a driver concept , > adapting OSS/Free or ALSA to allow RTLinux tasks to access the > sound drivers, and providing HARD REALTIME priority. > With such a system we will able to archieve <1-2ms latency, > close to the hardware limits of the soundcard, and without audio dropouts > even on the highest system load ( disk I/O , gfx etc.) , because > the entire Linux runs at the lowest priority. and is fully preemptable > by the RT Linux tasks. > It seems that RT Linux will go in to the main kernel thread with 2.4, > and for reliable very low-lantency audio ( <5ms) , RTLinux seems the > best way to go.
Benno,
Having looked at the RT-Linux documentation, my impression was that its task programming environment was even more restrictive than that for regular device drivers. That doesn't sound like a platform that will produce interesting audio applications.
My current understanding is that acheiving our audio latency goals depends on two things at the moment:
1) Less locking in the kernel. I understand that this is slowly coming about, but I'd like to be able to better track what can be expected when. Measuring where things are *now* is aided by programs such as your latencytest.
2) HZ > 100. This is so we can have something other than monolithic programs that open and get their timing from the soundcard. Apparently, this is easy to do now, but I wonder when it will mainstream and be available in some distributions.
Best of Real-Time,
Eric
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