Re: Understanding ComplexPlayThru
Re: Understanding ComplexPlayThru
- Subject: Re: Understanding ComplexPlayThru
- From: William Stewart <email@hidden>
- Date: Thu, 7 Sep 2006 14:51:29 -0700
On 07/09/2006, at 3:52 AM, Neil Clayton wrote:
On a more interesting note, I removed the Varispeed unit from the
graph and modified the code so that the DefaultOutput AU stream
format is set to the ouptut format of the AUHAL (element 1).
Now it all 'just works'. I read somewhere that the DefaultOutput
AU had a AudioConverter inside - so assuming that's right and I'm
not making it up, does this mean that the Varispeed is was required
some time in the past, but is no longer? (e.g: old code?)
No.
The varispeed is required to match the potentially different rates of
different and non-synchronised audio devices.
The sample rates should be getting handled like this:
Input Device SR - AUHAL (for input side) - Input of Varispeed
Output of Varispeed - AUHAL (for output side) - Output Device SR
In other words, the varispeed can and should do the rate conversion
(as well as the rate adjustments) between the device being used for
input and the device being used for output. You do this by making
sure that the sample rate between the input of the varispeed and the
device it is getting its data from is the same, and then that the
output of the varispeed is at the same sample rate that of the device
it is outputting its data too.
Bill
Neil
On 6/09/2006, at 9:33 AM, Neil Clayton wrote:
Hi Everyone.
I am currently looking through ComplexPlayThru in order to
understand it better. One of the tests I've been doing is to use
Soundflower as the input, and built-in-audio as the output.
Assuming both use the sample sample rate (which they do, as
confirmed in AMS) things work fine.
If I change the default output device to use a sample rate of
48000, then things are not quite as rosy. There is about 1s worth
of audio played, which is at a lower pitch (I think the varispeed
conversion ration was about 0.91 or thereabouts), and then it goes
pear shaped.
Pear shaped, for the moment I don't mind. What's confusing me is
that I would have thought he varispeed unit would have accounted
for the differences in sample rate, and therefore the audio
wouldn't be heard at a different pitch. Is this correct?
Regards,
Neil Clayton
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