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Re: [fluid-dev] Fluid/qsynth/rosegarden not giving stable audio output a

From: Robert Jonsson
Subject: Re: [fluid-dev] Fluid/qsynth/rosegarden not giving stable audio output after a while-Blame Jack
Date: Tue, 15 Mar 2005 17:47:19 +0100
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On Tuesday 15 Mar 2005 09:49, Marc Brevoort wrote:
> Hi,
> >Are you by any chance using an SB-Live with 44.1khz samplerate? If so this
> >is a known issue with this card, it works much better at 48khz.
> >If not... I don't know ;)
> Since this message I've identified the problem to be with the Jack Audio
> Connection kit only. If I configure qsynth/fluidsynth to playback directly
> via ALSA, the problem does not occur (of course, with the drawback that the
> synth output cannot be routed, for example, to freqtwear or rezound).
> Also, yes, I was running at 44.1 khz. The music is intended for burning to
> CD, and resampling from 48 khz to 44.1 in the end of the process introduces
> some (albeit not a lot) loss of quality. 

Quite true, though with good resampling algorithms this will probably not be 

For the record, fluidsynth must do resampling internally to accomodate for 
different sample rates, yes?

> Also I figured running at 44.1 
> should allow for about 10% more instruments because there's less to
> calculate.

Yes, the calculations will probably be more, though I think the bottlenecks 
are elsewhere, the difference should be nowhere near 10%.

> I realize that the problem is attributed to the card itself (an audigy, not
> a live, but also using an emu10k1, so it has the same problem). But if
> playing direct-to-ALSA can play back smoothly through the hardware at
> 44.1kHz, I see no reason why Jack using ALSA driver shouldn't be able to do
> the same, 

Interesting information, I'd also say that Jack seems to trigger this problem 
Actually I sometimes have a very similar problem with an envy24 based card 
(Delta 44) together with Jack. If there has been a particularily nasty 
drop-out (don't know what the error message is) then something seem to get 
misaligned, resulting in lots of strange noises.

> so to me this looks like a software problem. For now I'm running 
> Jack at 48 khz.
> The Jack list recommends this (playing at 48 khz) stating "please see if
> the problem still occurs then so that we can isolate it being a problem
> with jack or not), which seems to solve the audio stability problem,
> however Jack still quits on me after a while, so I'll take this problem to
> that list. They'll be thrilled to find out this particular problem in the
> end seems to be a software issue ;)

Heh, perhaps, though user experiences (good and bad) are very good information 
for any project.


> Best regards,
> Marc Brevoort
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