Re: bus count and channel info confusion
Re: bus count and channel info confusion
- Subject: Re: bus count and channel info confusion
- From: William Stewart <email@hidden>
- Date: Fri, 23 Jul 2004 12:25:37 -0700
On 21/07/2004, at 11:54 AM, Pavol Markovic wrote:
>
On 21.7.2004, at 19:34, Stefan Gretscher wrote:
>
>
> Am 20.07.2004 um 20:44 schrieb Pavol Markovic:
>
>> Example:
>
>> AU has 1 stereo and 6 mono outs.
>
>> It creates 7 buses.
>
>> On first bus it allows to set 2-8 channels via StreamFormat property
>
>> (this is for logic workaround, but NOT the right way)
>
>> On others it allows to set only 1 channel per element/bus
>
>>
>
>> (Currently only the first bus with 8 channels are used in Logic;
>
>> all 7 buses with mono/stereo channels are used in Live 4 and maybe
>
>> later in others.)
>
> Thanks for the clarification, I agree with your suggestion.
>
>
>
>> Additionally the AU checks the AudioChannelsLayout property, as it
>
>> expects the newer hosts with multibus/multichannel ability will also
>
>> check this. This is not needed for hosts that don't support more
>
>> channels then two per bus, as these will never try set more then two
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>> channels per bus.
>
> So you mean that if the host sets bus 1 to 8 outputs and does not
>
> specify an AudioChannelsLayout, the AU will know that it's bad old
>
> Logic-style. This sounds very reasonable to me as setting 8 outputs
>
> without setting AudioChannelsLayout is something that "nice" hosts
>
> shouldn't do from how I understand it.
>
>
Yes, exactly.
Well, except that this is making an assumption that is not always true.
For example. Lets say that I have an effect that can be set to any num
channels in to out as long as they are the same (this is the default
for most effects).
Now, I have a 6 channel stream.. Somewhere above my effect that stream
has some kind of surround/spatial characteristic. But the effect
doesn't know about this - it just takes 6 channels in and outputs 6
channels.
It does NOT support the AudioChannelLayout property. It doesn't need to
because it is just processing channels with no implications to if of
where those channels are spatially.
Therefore, we've specified that support of the ACL is optional and
should only be supported by those AU's that are doing something based
on spatial locations. So, our MatrixReverb supports this, as when it
generates a 4 or 5 channel output it does so based on the presumed
spatial location of those channels (as described by its ACL).
I guess you could argue that an AU Instrument is generating audio and
typically not processing it, so if it is outputting more than 2
channels it is likely to be doing so with some spatiality assumed. But
I'm loathe to make this a rule...
Bill
>
>
Pavol Markovic
>
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