Re: MatrixMixer info
Re: MatrixMixer info
- Subject: Re: MatrixMixer info
- From: James McCartney <email@hidden>
- Date: Mon, 17 Nov 2003 12:17:29 -0800
On Nov 17, 2003, at 5:43 AM, Robert Grant wrote:
>
Sekhar asked me to add my new found knowledge of the MatrixMixer to
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the Swiki so here it is:
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http://www.mat.ucsb.edu:8000/CoreAudio/76
>
>
Please feel free to correct any misstatements but I think it's got the
>
essentials and leaves out most of yesterday's random speculations ;-)
>
>
1. If an input bus is enabled it MUST be connected to an audio
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source.
true. This is a bug.
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This cannot be an effect - it must be a signal generator like a music
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device or audio file.
I'm not sure why you say this. The MatrixMixer doesn't know what is
upstream as long as the input is not returning an error, whatever you
connect should be OK.
>
2. If the channel layout of the input audio unit does not match
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the mixer input bus then the MatrixMixer will not accept input. Use
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kAudioUnitProperty_StreamFormat to fix them up.
I wouldn't use the words "channel layout" here. To us, channel layout
means the number and order of the channels (viz AudioChannelLayout).
That matrix mixer only cares about the number.
>
4. There are mutliple places that you can set volume levels (note
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that these are all on a channel basis not bus except for the global
>
volume):
Every crosspoint is affected by 4 volumes: input channel volume,
crosspoint volume, output channel volume, master volume.
>
b& kAudioUnitScope_Input - set the input level of this channel - your
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typical input fader level
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b& kAudioUnitScope_Global - set the crosspoint level. This is a
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coordinate in the matrix where the x-axis is defined by the input
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channels and the y-axis is defined by the output channels. A
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crosspoint element is identified as: (x << 16 | y)
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b& kAudioUnitScope_Global - set the global volume level of the mixer.
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This is a special "crosspoint" with the value: 0xFFFFFFFF which seems
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appropriate though I'm not sure what the use is? I set it to unity
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gain.
0xFFFFFFFF is the master volume. i.e. the volume multiplied by all of
the outputs.
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b& kAudioUnitScope_Output - set the output level of each channel -
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your master fader level.-
Not my terminology preference.. 0xFFFFFFFF is the master. These are
output channel gains.
james mccartney
apple coreaudio
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