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Realtime group scheduling doesn't know JACKRealtime group scheduling doesn't know JACKPosted Dec 21, 2010 5:26 UTC (Tue) by jebba (✭ supporter ✭, #4439)In reply to: Realtime group scheduling doesn't know JACK by jimparis Parent article: Realtime group scheduling doesn't know JACK
> Can you provide a more specific example setup where you'd see the problem you describe?
I'm not sure this answers your question exactly, but I used jackd/ardour with live musicians and they can definitely notice if the system is set to higher latencies when you have a mix of live players and earlier recorded tracks. It was easy enough to get the latencies low enough, but it was interesting to me to see them definitely notice the difference.
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Realtime group scheduling doesn't know JACK Posted Dec 21, 2010 17:42 UTC (Tue) by drag (subscriber, #31333) [Link]
To get a idea of the scale we are talking about...
The speed of sound in a low humidity environment is going to be something like 350 to 400 meters per second. I've heard that humans can't distinguish 10msec from instantaneous. That would be somebody standing about 4 meters away from you making a sound.
Probably 100msec is acceptable, I figure. From end to end. It'll sound like your standing a ways away in terms of response, but you can compensate.
But if you tune your system to deliver 30msec performance and Linux will randomly have latency spikes past 150 msec every time a disk is accessed then it's worthless to you.
Realtime is about being able to provide deterministic latency.... Linux can't deliver reliable performance without realtime configurations. You can't really tell what latencies you can rely on because the system is not configured to behave in that way. It will be optimized for batch processing and server workloads and in that you can latencies all over the place as long as that will deliver the best performance in the long run.
Realtime group scheduling doesn't know JACK Posted Dec 22, 2010 16:24 UTC (Wed) by Cyberax (✭ supporter ✭, #52523) [Link]
>The speed of sound in a low humidity environment is going to be something like 350 to 400 meters per second. I've heard that humans can't distinguish 10msec from instantaneous. That would be somebody standing about 4 meters away from you making a sound.
Human ear can distinguish about 500 microsecond difference. I.e. a difference in distance of about 20 centimeters. Humans use this for directional hearing.
That's why smallest possible latencies are so important.
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