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Gear / Technical Help => Post-Processing, Computer / Streaming / Internet Devices & Related Activity => Topic started by: rjp on March 21, 2010, 12:58:26 AM
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Back here (http://taperssection.com/index.php?topic=108255.msg1588349#msg1588349), I had been having trouble with my E-MU 0404 USB audio box whenever I tried it with any of three different laptops under Windows. At that time, Linux wasn't even an option, as the drivers either didn't work at all or maxed out at 16/48. My workaround has been to just use it as an analog preamp to my LS-10 (which works very nicely).
Well, I decided to give Fedora 12 a try, and, surprise! All sampling rates are available, at 16- and 24-bit depths. I installed a copy on my Acer Aspire One netbook and recorded some 24/96 line-in "footage" played by a different system. As long as I don't use any networking, both record and playback work without any clicks, pops, or other extraneous noises. This same netbook using XP was a lost cause for recording, no matter how many devices I disabled.
A desktop system with Fedora 12 exhibited none of the networking-related problems... just as my XP desktop worked flawlessly with the 0404. At any rate, if I'm going to be taping with a laptop, network access is about the last thing I'd be concerned with.
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Networking pops can be eliminated by using a low latency kernel and running the sound daemon with realtime priority.
/etc/security/limits.conf
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@audio - rtprio 99
@audio - nice -10
@audio - memlock 65536
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/boot/config (default kernels configuration)
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CONFIG_HAVE_LATENCYTOP_SUPPORT=y
#
CONFIG_HZ_1000=y
CONFIG_HZ=1000
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Or something like that. Jackd with -R and other means to an end depending on how you have audio configured on your system. You don't have to disable the network (although it's not a bad ideal to free up resources to avoid potential issues). Note that memlock is whatever your system can spare. On my 3yo laptop with 512MB of RAM, and an integrated video card with 128MB shared RAM, not much to spare on that one.
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It's been years since I rolled my own kernel... but that might be interesting to try if I ever need networking on the netbook while recording.
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As it turns out, Ubuntu Studio (http://ubuntustudio.org/) ships with the realtime kernel, and works well with my E-MU interface. The only unfortunate thing is that the Wi-Fi driver doesn't get along with my Acer Aspire One's wireless - I get data corruption. That means I'll need to either use the wired network or sneakernet to transfer recordings made with it.
I'll have to see how my ThinkPad T30 copes with this - it has a quieter fan, at any rate, so it would be a better choice for my needs.