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

[Robert Jonsson]

Hi,

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 
audible. 

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 
easily. 
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.

/Robert


>
> Best regards,
> Marc Brevoort
>
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