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Re: Multichannel and AU
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Re: Multichannel and AU


  • Subject: Re: Multichannel and AU
  • From: Pavol Markovic <email@hidden>
  • Date: Fri, 7 May 2004 14:26:54 +0200

As far as I know, current DP4 release version does not support multichannel AU, only MAS. GarageBand is single bus (mono/stereo) only I think.

PM

On 7.5.2004, at 10:43, Hans Mvller wrote:

I have now a 8 stereo channel or 16 mono channel solution working with AUValidation tool to but sill not working with DP 4.1 or Grageband. Does anybody got 8 stereo channel to work in either DP 4.1 or Garagenband?

Regards
Hans Mvller
onsdagen den 5 maj 2004 kl 19.54 skrev Pavol Markovic:

Is there any host that supports this? I've tried negative values in Logic Pro 6.4.1 and my synth was not recognized then.

On 3.5.2004, at 21:44, William Stewart wrote:

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
/Developer/Documentation/CoreAudio/AudioUnits/
IOChannelConfigurations.rtf ChannelInfo must return { 0, 16 }, because
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
publish a channel info using this semantic of a total number of
channels and not to have that scope's element count writable."). The
host can guess from the initial setting how many Busses there are at
maximum. It's more or less clearly explained in the HTML docs for
kAudioUnitProperty_BusCount: "Other units, such as Mixer units, may
have already allocated the necessary state to accept a number of
inputs, so this call can be used to determine that limit. "

I think, the explicit semantics must be negotiated between host and
plugin when setting the ChannelLayout property (which I havn't
explored so far...)

Then, the host should give you a Render Call for each Output.

(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,

;) Urs



Am 27.04.2004 um 14:21 schrieb Hans Mvller:

Thanks Urs.

This is probably the solution, but how can the plugin work in Logic(I
forgot to mention this in the last mail)?

/Hans
tisdagen den 27 april 2004 kl 13.25 skrev Urs Heckmann:

Hiya Hans,

at first glimpse: 8 Stereo outs equal 8 Busses.

Set the Output Scope Elements count in the MusicDevice derived
constructor to 8 rather than 16...

The ChannelInfo Property should only return a stereo pair { 0, 2 },
which then counts for all busses (If I'm not completely mistaken)

Hope this helps,

;) Urs


Am 27.04.2004 um 12:39 schrieb Hans Mvller:

Hello

Im trying to get a multichannel(8 stereo channels) AU to work in
Motu DP 4.1 and Garageband. The probelm is that is not shown.

Im also get the following error message in au validation tool.

--------------------------------------------------
VERIFYING DEFAULT SCOPE FORMATS:
Input Scope Bus Configuration:
Default Bus Count:0
Output Scope Bus Configuration:
Default Bus Count:16
Default Format: AudioStreamBasicDescription: 2 ch, 44100 Hz,
'lpcm' (0x0000002B) 32-bit big-endian float, deinterleaved
ERROR: Default Format of unit does not match reported Channel
handling capabilities
* * FAIL

urs heckmann
email@hidden
www.u-he.com
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References: 
 >Re: Multichannel and AU (From: Hans Möller <email@hidden>)

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