Re: AUConverter crackling
Re: AUConverter crackling
- Subject: Re: AUConverter crackling
- From: Dave Addey <email@hidden>
- Date: Thu, 12 Feb 2004 20:25:43 +0000
Hi Bill,
Did you ever write a readme about this? Also, is there documentation in the
pipeline for the AUVarispeed and how to use it alongside AudioUnits? I'm
actually gearing up to hook up several streams to a MatrixMixer, but need to
be able to vary the pitch (without crackling) of the streams coming into it
independently, in realtime. I guess this is a AUVarispeed task, right?
Was AUVarispeed in QT 6.4 too? Or 6.5 only?
Also, think I said this here before, but if the AUVarispeed ever ends up
time stretching as well, that'd be *great* :-)
Thanks in advance,
Dave.
>
From: William Stewart <email@hidden>
>
Date: Tue, 13 Jan 2004 11:44:45 -0800
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To: John Stiles <email@hidden>
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Cc: email@hidden
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Subject: Re: AUConverter crackling
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>
On 13/01/2004, at 11:33 AM, John Stiles wrote:
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>
> How does this compare to k3DMixerParam_PlaybackRate?
>
>
This appears in the Panther distribution (and the QT 6.4 or later
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release for Jaguar)
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>
This parameter co-operates with a cheap (linear) resampling algorithm
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that we added to the 3D Mixer's inputs. Basically they work as follows:
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The 3DMixer will accept a mismatch between the sample rate of any of
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its inputs and its output sample rate. If there is a mismatch, a cheap
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linear resampling will be done to the input data to bring it to the
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output sample rate. The quality of course is not that high, but for
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games linear resampling is the norm (that is what the sound blaster
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uses for instance)...
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>
Now, additionally, we've added a parameter to each input that allows an
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input to be played faster (or slower) than its nominal rate - this is
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done through using this resampling as well of course, but it is dynamic
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in the same way that the AUVarispeed is dynamic, and can be tweaked as
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often as you like.
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>
Meant to write a read me about this - so thanks for the question John
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>
Bill
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>
> (When was this added, BTW? If a user has installed QuickTime 6.5, can
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> we rely on it being there in 10.2.x?)
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>
>
>
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> On Jan 12, 2004, at 3:44 PM, William Stewart wrote:
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>
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>> Yes indeed that does sound like the same problem. The AC's resampler
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>> is NOT about dynamic adjustment (that's why to get a different sample
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>> rate you have to make a new audio converter) and also why we have the
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>> varispeed AU.
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>>
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>> Bill
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>>
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>> On 12/01/2004, at 7:21 AM, Hugues Pisapia wrote:
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>>
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>>> Well,
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>>>
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>>> I went back into this thread and it seems to be also a problemk I am
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>>> experiencing... I'm using the HAL through Java to access the
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>>> recording (and playback) facilities. I want to perform resampling on
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>>> the fly and get crackling sound, apparently, between each chunk of
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>>> audio that go throught the AC.
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>>>
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>>> Is that the same problem, and do I have to use the AudioUnits as
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>>> well? If so... What is the AC for?
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>>> Hugues
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>>>
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>>> Stefan Werner wrote:
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>>>
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>>>> Hi,
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>>>>
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>>>>> To: email@hidden
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>>>>> From: Chris Rogers <email@hidden>
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>>>>> Subject: Re: AUConverter crackling
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>>>>>
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>>>>> The AudioConverter is not designed to change sample-rate on the
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>>>>> fly like
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>>>>> this. The AUVarispeed AudioUnit should be perfectly adapted to
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>>>>> this
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>>>>> application by tweaking the "rate" parameter on the fly.
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>>>>
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>>>>
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>>>> OK, I'll try that. Is it using FFT or is it doing simple
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>>>> resampling? I need the latter, that's why I tried the AUConverter.
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>>>> To me, AUVarispeed sounded more like timestretching than
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>>>> resampling.
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>>>>
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>>>> I suppose there's no other documentation than the WWDC presentation
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>>>> Bill mentioned?
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>>>>
>
>>>> Stefan
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>>>>
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>>>> http://www.hdm-stuttgart.de/~sw19/audiospace/
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>>
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________________________________________________________________________
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__
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"Much human ingenuity has gone into finding the ultimate Before.
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The current state of knowledge can be summarized thus:
>
In the beginning, there was nothing, which exploded" - Terry Pratchett
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