Subject: Re: [linux-audio-dev] BruteFIR + jack = crackling noise?
From: Martijn Sipkema (msipkema_AT_sipkema-digital.com)
Date: Mon Feb 24 2003 - 17:54:56 EET
[...]
> many USB audio interfaces work in a fundamentally different way than
> other audio interfaces. rather than sending an "interrupt" to the host
> after processing 2^N frames, they send an interrupt every N
> msecs.
And JACK doesn't support this because it needs a constant size
(frames) period. IMHO the audio interface should dictate the period
size and it need not be constant.
Perhaps you would reconsider having JACK use constant (frames)
callbacks?
[...]
> in closing, let me say that the fact that there are lots of USB audio
> interfaces appearing shouldn't fool anyone into thinking that these
> are suitable for professional audio work. the basic design of USB is
> terrible for this stuff, and i would personally avoid USB audio
> interfaces like the plague.
For good performance the period should be constant, but it doesn't
really matter if it is contant frames of constant time with a possible
very small difference in frames. USB may have more problems, I
don't know really, but the period size is not really a big problem, or
at least it shouldn't be.
> the old joke "eat shit - 600 billion
> flies can't be wrong" seems very to much to apply here, IMHO.
You are probably right. This is also the case, or perhaps even more
so with (the standard) USB over MIDI.
--ms
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