Re: Multichannel and AU
Re: Multichannel and AU
- Subject: Re: Multichannel and AU
- From: William Stewart <email@hidden>
- Date: Mon, 3 May 2004 12:44:54 -0700
On 03/05/2004, at 4:33 AM, Urs Heckmann wrote:
>
Hi Hans,
>
>
Sorry, I must correct myself 8-(
>
>
You keep the 8 output Busses, but, as described in
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/Developer/Documentation/CoreAudio/AudioUnits/
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IOChannelConfigurations.rtf ChannelInfo must return { 0, 16 }, because
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this adds up the total number of channels for all Busses.]
No... channel info reports that ability of each/every bus to support a
given number of channels... Thus, the DLS Synth reports {0, 2} - it has
two output buses, and each of these can only support stereo channels.
It is *NOT* the total number of channels across the buses if the number
>
0.
If the number is < 0, then it is the total number of channels across
all the buses, *regardless* (and this is important) of how the host
decides to configure each individual bus. Thus:
{ 0, -16 }
Indicates you can support up to 16 channels of output, and as a host I
can configure any number of buses with any number of channels on each
bus as long as the total number of channels is <= 16.
The negative number here is *extremely* important!!!
>
Then, you must make your BusCount property writable ("It is illegal to
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publish a channel info using this semantic of a total number of
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channels and not to have that scope's element count writable."). The
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host can guess from the initial setting how many Busses there are at
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maximum. It's more or less clearly explained in the HTML docs for
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kAudioUnitProperty_BusCount: "Other units, such as Mixer units, may
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have already allocated the necessary state to accept a number of
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inputs, so this call can be used to determine that limit. "
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>
I think, the explicit semantics must be negotiated between host and
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plugin when setting the ChannelLayout property (which I havn't
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explored so far...)
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>
Then, the host should give you a Render Call for each Output.
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>
(I hope I got it correct this time)
Nearly.
If you have a look in the current SDK in Public Utility/CAAudioUnit
there is all the logic there that a host needs to both discover and
configure an AU that supports this "dynamic configuration" of in/out
buses and channels per bus.
Bill
>
>
Cheers,
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>
;) Urs
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>
>
>
Am 27.04.2004 um 14:21 schrieb Hans Mvller:
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>
> Thanks Urs.
>
>
>
> This is probably the solution, but how can the plugin work in Logic(I
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> forgot to mention this in the last mail)?
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>
>
> /Hans
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> tisdagen den 27 april 2004 kl 13.25 skrev Urs Heckmann:
>
>
>
>> Hiya Hans,
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>>
>
>> at first glimpse: 8 Stereo outs equal 8 Busses.
>
>>
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>> Set the Output Scope Elements count in the MusicDevice derived
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>> constructor to 8 rather than 16...
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>>
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>> The ChannelInfo Property should only return a stereo pair { 0, 2 },
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>> which then counts for all busses (If I'm not completely mistaken)
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>>
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>> Hope this helps,
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>>
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>> ;) Urs
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>>
>
>>
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>> Am 27.04.2004 um 12:39 schrieb Hans Mvller:
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>>
>
>>> Hello
>
>>>
>
>>> Im trying to get a multichannel(8 stereo channels) AU to work in
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>>> Motu DP 4.1 and Garageband. The probelm is that is not shown.
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>>>
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>>> Im also get the following error message in au validation tool.
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>>>
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>>> --------------------------------------------------
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>>> VERIFYING DEFAULT SCOPE FORMATS:
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>>> Input Scope Bus Configuration:
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>>> Default Bus Count:0
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>>> Output Scope Bus Configuration:
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>>> Default Bus Count:16
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>>> Default Format: AudioStreamBasicDescription: 2 ch, 44100 Hz,
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>>> 'lpcm' (0x0000002B) 32-bit big-endian float, deinterleaved
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>>> ERROR: Default Format of unit does not match reported Channel
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>>> handling capabilities
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>>> * * FAIL
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>>>
>
>> urs heckmann
>
>> email@hidden
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>> www.u-he.com
>
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