linuxaudio.org

--_157f0c97-0c25-409a-98ac-7f03947b860b_

Content-Type: text/plain; charset="iso-8859-1"

Content-Transfer-Encoding: quoted-printable
> Date: Mon=2C 12 Mar 2012 09:11:46 +1100

quoted text
> From: lsd@wootangent.net

> To: linux-audio-user@lists.linuxaudio.org

> Subject: Re: [LAU] Popping sound at the start of every note on Bristol	sy=

nths.

quoted text
>=20

> On 12/03/12 9:03 AM=2C Rafael Vega wrote:

> > However=2C I've found that there is a popping sound at the start of eve=

ry

quoted text
> > note. This is more apparent in some models/presets than others. I'm

> > pretty sure my jack configuration is fine (has been working fine with

> > other synths=2C ardour=2C puredata=2C qtractor=2C etc.) and I've also t=

ried ALSA

quoted text
> > and two different sound cards (laptop internal and firewire). I also

> > tried outputting Bristol straight to system output=2C passing through

>=20

> It may just be that the attack on the amplitude envelope is too fast.=20

> I'm not sure if Bristol has this problem=2C but on many synths=2C with th=

e=20

quoted text
> attack time set to its minimum=2C the envelope opens instantaneously=2C a=

nd=20

quoted text
> that can cause a clicking sound. Try increasing the attack time and see=20

> if that helps.

>=20

> Thanks

I had a listen through the sample you posted and agree that it is an issue =

withthe attack time=2C it was always very aggressive but there was also a r=

ecent changefrom a default exponential to default linear attack which proba=

bly does not helpwith what you are hearing. You can change back to exponent=

ial from the configstage however there is _another_ change that will go int=

o the next release whichis probably the correct fix.

The change is to make the envelope 'time constant'. This is actually not th=

e casewith the current code so if you increase the sampling rate you also i=

ncrease thefastest attack rate. The fix places the attack at 500us then giv=

es you a rate which is independent of the sampling rate. I can make this a =

config time option if peopleare interested=2C it could be a runtime option =

which I think that is overkill but 500us is still pretty aggressive.

The maximum attack duration does not change=2C that is also a config option=

 which defaults to 10 seconds however having the parameters being a functio=

n of the sampling rate was bad coding.

FYI some background on the changes: I have been doing work on 'low end'syst=

ems where I default to half rate sample=2C 22KHz and 24KHz to reduce the CP=

Ufootprint and hence extend battery life. At the same time I have been work=

ing onhigh end systems where we have been reviewing the improved sound qual=

ity with96KHz and 192KHz and these really exacerbated the problem. There ar=

e other interesting results from the developments. The main filters are Huo=

vilainen's whichare 2x resampling=2C this was required since the algorithm =

loses frequency accuracyas it approaches Nyquist. At the higher rates I rem=

oved the resampling since the cutofffrequency is now nowhere near Nyquist a=

nd the result is that=2C for the filters at least=2Cthe change from 48 to 9=

6KHz is almost free and you can still 'play' the filter at selfoscillation.

Let me review the code differences and perhaps post the new envelope.c on t=

heSourceForge forum. That might not be possible: the envelopes actually dri=

ve thesignalling to the engine regarding when to deactivate voices in polyp=

honic voiceassignments and I don't want any more sticky or lost notes where=

 this signallingmight have changed.

Regards=2C nick. 		 	   		  =
--_157f0c97-0c25-409a-98ac-7f03947b860b_

Content-Type: text/html; charset="iso-8859-1"

Content-Transfer-Encoding: quoted-printable
&gt=3B Date: Mon=2C 12 Mar 2012 09:11:46 +1100&gt=3B From: lsd@woo=

tangent.net&gt=3B To: linux-audio-user@lists.linuxaudio.org&gt=3B S=

ubject: Re: [LAU] Popping sound at the start of every note on Bristol	synth=

s.&gt=3B &gt=3B On 12/03/12 9:03 AM=2C Rafael Vega wrote:&gt=3B=

 &gt=3B However=2C I've found that there is a popping sound at the start of=

 every&gt=3B &gt=3B note. This is more apparent in some models/presets =

than others. I'm&gt=3B &gt=3B pretty sure my jack configuration is fine=

 (has been working fine with&gt=3B &gt=3B other synths=2C ardour=2C pur=

edata=2C qtractor=2C etc.) and I've also tried ALSA&gt=3B &gt=3B and tw=

o different sound cards (laptop internal and firewire). I also&gt=3B &g=

t=3B tried outputting Bristol straight to system output=2C passing through<=

br>&gt=3B &gt=3B It may just be that the attack on the amplitude envelo=

pe is too fast. &gt=3B I'm not sure if Bristol has this problem=2C but =

on many synths=2C with the &gt=3B attack time set to its minimum=2C the=

 envelope opens instantaneously=2C and &gt=3B that can cause a clicking=

 sound. Try increasing the attack time and see &gt=3B if that helps.&gt=3B &gt=3B ThanksI had a listen through the samp=

le you posted and agree that it is an issue withthe attack time=

=2C it was always very aggressive but there was also a recent change<=

div>from a default exponential to default linear attack which probably does=

 not helpwith what you are hearing.&nbsp=3BYou can change back to exponential from the configstage however there is _another_ change that will go into the next =

release whichis probably the=

 correct fix.The change is to make the=

 envelope 'time constant'. This is actually not the case<=

span style=3D"font-size: 10pt=3B ">with the current code so if you increase=

 the sampling rate you also increase thefastest attack rate. The fix places the attack at 500us =

then gives you a rate which&nbsp=3Bis independent of the sampling rate. I can make this a config=

 time option if peopleare interested=2C it could be a runtime option which I think that is overk=

ill but 500us&nbsp=3B=

is&nbsp=3Bstill pretty aggressiv=

e.The maximum attack duration does not=

 change=2C that is also&nbsp=3Ba=

 config&nbsp=3Boption which&nbsp=

=3Bdefaults to 10 sec=

onds however having the parameters being a function of the&nbsp=3Bsampling rate was bad coding.<=

/span>=

FYI some background on the changes: I have been doing work on 'low end'systems where I default to half rate sample=2C 22KHz and 24KHz to re=

duce the CPUfootprint and hence extend battery life. At the same=

 time I have been working onhigh end systems where we have been =

reviewing the improved sound quality with96KHz and 192KHz and th=

ese really exacerbated the problem. There are other&nbsp=3Binter=

esting results from the developments. The main filters are Huovilainen's wh=

ichare 2x resampling=2C this was required since the algorithm lo=

ses frequency accuracyas it approaches&nbsp=3BNyquist. At the hi=

gher rates I removed the resampling since the cutofffrequency is=

 now nowhere near&nbsp=3BNyquist&nbsp=3Band the result is that=2C for the f=

ilters at least=2Cthe change from 48 to 96KHz is almost free and=

 you can still 'play' the filter at selfoscillation.<=

br>Let me review the code differences and perhaps post the new e=

nvelope.c on theSourceForge forum. That might not be possible: t=

he envelopes actually drive thesignalling&nbsp=3Bto the engine r=

egarding when to deactivate voices in polyphonic voiceassignment=

s and I don't want any more sticky or lost notes where this signallingmight have changed.Regards=2C nick. 	=
=
--_157f0c97-0c25-409a-98ac-7f03947b860b_--