Re: Channels and frames
Re: Channels and frames
- Subject: Re: Channels and frames
- From: "john smith" <email@hidden>
- Date: Thu, 03 Nov 2005 20:13:53 +0100
William,
thanks for the reply, but I think there's been some misunderstanding. If I
understand you correctly, then you're talking about the first bus here,
something I now know how to configure.
My question is regarding a second bus (for side-chain). How do I configure
the channel count for that?
1 input channel, and 1 output channel). You cannot have mixed channel
counts on input or output buses.
Do you mean to say that if the channel count is, say, 2,2 for the first bus,
then it will always be the same for the second bus?
If so, what happens to the output channel(s) of the second bus? Should I
zero it, or copy from the input?
The approach we take to this is that if the AU is going to deal with
uneven channel counts (mono input and stereo output), then it has to be
prepared to deal with the full ramifications of that feature.
I'm sorry, I don't understand. What ramifications? Do you mean to say that
1,2 is not supported?
Thanks,
Michael Olsen
Here are your choices:
* { {2, 2} {1, 1} }
What this means is that regardless of your number of buses, the AU can be
configured to have 2 input channels and 2 output channels (or 1 input
channel, and 1 output channel). You cannot have mixed channel counts on
input or output buses.
* { {2, 2} {1, 1}, {1, 2} }
That is, you want to allow mono or stereo inputs and stereo outputs, and
for a mono output only mono inputs are legal.
(And for completeness)
* { {2, 2} {1, 1}, {2, 1} }
That is, you want to allow mono or stereo inputs and mono output, and for
a stereo output only stereo inputs are legal.
* { {2, 2} {1, 1}, {2, 1}, {1, 2}}
Any combination of mono or stereo inputs or outputs are allowed.
The approach we take to this is that if the AU is going to deal with
uneven channel counts (mono input and stereo output), then it has to be
prepared to deal with the full ramifications of that feature. We've looked
at ways to somehow publish more restricted lists, but don't like the
complexities this involves.
You can use AU Lab => /Developer/Applications/Audio to test this - is has
support for input and output side chains. CAAudioUnit (in PublicUtility in
the SDK) has code to validate channel configurations if you want to look
at how the host deals with these. auval will correctly validate these
configs.
Bill
On 03/11/2005, at 7:36 AM, john smith wrote:
Hi,
Please disregard my previous question about the output bus. I think I
understand it now.
But... (and someones gonna kill me for asking.)...
an additional "sidechain" input for AU effects is described as a
separate bus - so in your case the AU must specify that it can handle
mono and stereo inputs and outputs (config list: [1,1], [2,2]) and it
must provide two input busses and one output bus.
How can I inform the host about the channel count on the second bus?
And how can I make sure that it only connect with 1 channel on the second
bus when running in mono mode, and with 2 channels on the second bus when
running in stereo mode?
(i.e. avoid mono sidechains when running in stereo and vice versa).
Thanks,
Michael Olsen
Best,
Stefan
Am 03.11.2005 um 12:35 schrieb john smith:
I'm about to create a channel strip product for a client.
Besides the "usual" channel configurations (1->1, 1->2, 2->2) it has
some alternative configurations, namely 2->1 and 4->2. The thing about
those configurations is that they have extra side- chain inputs.
For instance, the one I call 2-> has 1 audio in, 1 side-chain in (which
is of course also audio, but I'm sure you're catching my drift), and 1
audio out.
My question is: If I tell the host (Logic or otherwise) that I can
accept 2 channels in and 1 channel out, will the host know what the
second input is a side-chain input?
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