What are the functional definitions for the input and output ports?
For example, I noticed that the default is 1 input (channel 0) and 1 output (channel 0), which seems to be a full stereo in/out. Is this correct?
If I assign 2 inputs and 2 outputs, it seems to assign Left to channel 0 and Right to channel 1. Is this correct?
Now, what if I assign 3,4,5... inputs or outputs? What do they do?
Is there a spec out there that explains all this?
-Dan
Input/Output assignments
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- KVRer
- 10 posts since 4 Mar, 2009
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- KVRer
- 12 posts since 13 Dec, 2008
Hi Dan,
You are correct on stating that the first two channels are the L and R channels.
One channel (channel 0) would be mono, and I believe it is up to the host how this is used. e.g the plugin only appears on mono tracks or the ability to work on "multi mono", which is using a mono plugin on a stereo or surround track.
If I can remember correctly, channel 2 (3rd channel) is the LFE or the .1 in a 5.1 / 7.1 / x.1 setup
channel 3 the center, channel 4 the left surround, channel 5 the right surround.
There is no official spec out there, this is what I found through experience/trial and error. I recently started building a 5.1 delay plugin and so I switched to SonicBirth from C++. While simple stereo plugins I can just about manage to write in code, 6 ins and 6 outs is just too much to handle for now.
You are correct on stating that the first two channels are the L and R channels.
One channel (channel 0) would be mono, and I believe it is up to the host how this is used. e.g the plugin only appears on mono tracks or the ability to work on "multi mono", which is using a mono plugin on a stereo or surround track.
If I can remember correctly, channel 2 (3rd channel) is the LFE or the .1 in a 5.1 / 7.1 / x.1 setup
channel 3 the center, channel 4 the left surround, channel 5 the right surround.
There is no official spec out there, this is what I found through experience/trial and error. I recently started building a 5.1 delay plugin and so I switched to SonicBirth from C++. While simple stereo plugins I can just about manage to write in code, 6 ins and 6 outs is just too much to handle for now.
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- KVRer
- Topic Starter
- 10 posts since 4 Mar, 2009
Thanks for the info... that's a lot more than I have been able to find in my web search. I even looked through the Apple AU SDK, but didn't find anything relating to this.
By the way, if you assign only one input (0) and output (0), full stereo DOES go through the plug-in (I proved it with a special test track). However, very odd things happen if the signal is processed with a time-varying function, such as an auto-filter. Separations in the stereo image start happening, with lots of unintended panning and Leslie-like effects.
My theory is that the input signal is actually serially multiplexed stereo (L-R-L-R...), so a time-varying function does not end up affecting both channels equally.
Try making a bandpass filter with an LFO sweeping the center freq in this one-channel mode to hear what I am talking about. It is kind of a cool effect, but not too subtle!
If I create 2 inputs and outputs, and make duplicate filter circuits for left and right, the panning and wooshing effects go away and everything behaves normally.
-Dan
By the way, if you assign only one input (0) and output (0), full stereo DOES go through the plug-in (I proved it with a special test track). However, very odd things happen if the signal is processed with a time-varying function, such as an auto-filter. Separations in the stereo image start happening, with lots of unintended panning and Leslie-like effects.
My theory is that the input signal is actually serially multiplexed stereo (L-R-L-R...), so a time-varying function does not end up affecting both channels equally.
Try making a bandpass filter with an LFO sweeping the center freq in this one-channel mode to hear what I am talking about. It is kind of a cool effect, but not too subtle!
If I create 2 inputs and outputs, and make duplicate filter circuits for left and right, the panning and wooshing effects go away and everything behaves normally.
-Dan
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- KVRer
- 12 posts since 13 Dec, 2008
No problem dude.
Interesting anomaly, and a valid theory to fit.
Also, looks like you've found one of those useful accidents. Well done! Explaining this effect is beyond me but it indeed does sound very cool!
Interesting anomaly, and a valid theory to fit.
Also, looks like you've found one of those useful accidents. Well done! Explaining this effect is beyond me but it indeed does sound very cool!