Realtime is also needed for multimedia [LWN.net]

Realtime is also needed for multimedia

Posted Dec 6, 2007 18:27 UTC (Thu) by ssavitzky (subscriber, #2855)
Parent article: Enterprise realtime and cooperative development

I'm not an enterprise, I'm an amateur musician with a bedroom studio.  If I don't have a
low-latency kernel (obtainable from, e.g., 64studio or ubuntustudio) I can't record audio
without dropouts.

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Realtime is also needed for multimedia

Posted Dec 7, 2007 1:22 UTC (Fri) by giraffedata (subscriber, #1954) [Link]

If I don't have a low-latency kernel (obtainable from, e.g., 64studio or ubuntustudio) I can't record audio without dropouts.

s/low-latency/bounded-latency

These kernels have greater latency on average than kernel.org. They just have better worst-case latency.

Realtime is also needed for multimedia

Posted Dec 7, 2007 4:13 UTC (Fri) by ssavitzky (subscriber, #2855) [Link]

That would be more nearly correct, though whether they're better or worse on average probably
depends on the exact workload.

I believe that, originally, they really did have lower latency; many of those patches have
made it into the mainstream kernels because they also improved performance on SMP systems by
making more of the kernel pre-emptable.

Realtime is also needed for multimedia

Posted Dec 7, 2007 16:50 UTC (Fri) by niv (subscriber, #8656) [Link]

Do you futz around with the priority of your application, though? I'd be interested in hearing
what your experience was in terms of latencies.

Realtime is also needed for multimedia

Posted Dec 8, 2007 4:16 UTC (Sat) by ssavitzky (subscriber, #2855) [Link]

I don't normally tweak priorities, but I don't usually have anything running when I'm
recording except Audacity, an xterm, and X.  I've found that you want to use a separate video
card rather than one that shares main memory, and you want to turn off the DRI (Direct
Rendering Interface) in the X server config file.  

Recording onto an NFS-mounted filesystem is dicey.

Realtime is also needed for multimedia

Posted Dec 11, 2007 1:55 UTC (Tue) by RobertBrockway (subscriber, #48927) [Link]

Perhaps you don't want to run X on the box at all.  X is network transparent so you can
display Audacity to another box on the network.  Yes this means involving another box (or a
thin client) but it _might_ give better performance.

Realtime is also needed for multimedia

Posted Dec 11, 2007 14:31 UTC (Tue) by ssavitzky (subscriber, #2855) [Link]

I actually recorded about 2/3 of my CD that way -- it worked, but there was a noticable lag that made it less responsive for editing and overdubbing. My current recording box is a dual-core CPU, which gives me the best of both worlds.