Subject: [linux-audio-dev] BruteFIR + jack = crackling noise?
From: Werner Johansson (wj_AT_yodel.net)
Date: Mon Feb 24 2003 - 15:48:09 EET
Hi all!
First post to this list for me..
I have observed a strange thing with my jackd + BruteFIR setup, it looks something like this:
HW: Emagic 2|6 USB thing (hw0), directly connected to a USB port, no hubs.. This runs with both inputs and outputs in analog mode for now to rule out any kind of sample rate/clock rate mismatches digital mode can introduce.
Kernel 2.4.19-1LL (running Planet CCRMA software here with lowlatency enabled in the kernel) - have tried this on both a RedHat 7.3 and RedHat 8.0 system.
jackd -R -d alsa -d hw:0 -r 44100 -p 2048
BruteFIR running at 44100Hz with a filter size of 2048,8
This gives me a faint crackling noise in the output (sounds like latency issues, but nothing gets logged anywhere).. The symptom is the same for 48kHz, and to make sure that's it not really anything directly hardware related I can start jack up and instead of connecting BruteFIR I can connect AlsaPlayer and play MP3's or whatever just fine (!)...
That's not the most interesting part though - the crackling disappears if I choose a filter size of 4096,4 (or 8) instead, with the same period size for jack - that really shouldn't make any difference, should it??
Anyone else that have seen/heard this problem, or is it just me? :)
It seems that my 2|6 likes period sizes of 44100/1000 or 48000/1000 much better than the BruteFIR-enforced 2^something sizes though - I can't reliably play anything using a period size of 1024, but one of 820 is fine @ 44100Hz rate (?)
What other information would be relevant here?
/WernerJ
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