With a project I’m working on, I’ve started to modulate the Fader gain on many busses using sidechain signals from other busses. I’m keen to connect many busses and create a sort of complex web of sidechain connections but I’m hesitant about how much CPU that might use. So my question is, how resource intensive is that? How does it compare to using actual compressors? What about using a sidechaing signal to modulate the frequencies on an EQ3/multiband EQ? How do I properly measure the affect of doing lots of this stuff? And how worried should I be about using lots of sidechains?
On paper, the main performance point for compressors vs sidechains would be whether a compressor is working in linked mode. Linked mode will collapse the sidechained signal to mono before processing, so the theoretical overhead should be roughly similar to sidechain modulation which essentially does the same. If the compressor isn’t in linked mode, then all channels in the signal will be processed individually instead of just a single mono channel, introducing, for example, 6 channels for a 5.1 signal instead of just 1 channel.
However, in general I would recommend implementing the behavior you want in the way that gives you control over the signal in the way you need it (compressor’s linked vs unlinked modes, sidechain modulator’s peak vs RMS), and then connecting to your application via Live Update and using the profiler to record a session of the project to help narrow down problem areas.
It means that if you sidechain a VCA’s gain using 10 different inputs, it will only count as 10 channels to process, as opposed to 10 times the amount of channels each signal is using - i.e. 10 * 6 channels in a 5.1 signal.
I have a most probably unoptimal sidechaining setup going, where some VCAs are being sidechained by 20-25 different audio busses. I’m guessing it would be a lot more CPU efficient if I restructured my busses in a way that allowed me to use far less input signals for sidechaining. Is this correct?
What’s the best way for me to be measuring the impact of this sidechaining? Would checking the CPU measurements before/after in the profiler be a good way to do it?
Edit: And also, is there any difference between sidechaining on a bus vs sidechaining on a VCA?
Doing a before/after in the profiler is probably the best way, yes. I’d recommend duplicating your project when you do so though, especially based on what you’ve said about the complexity of the sidechaining.
The actual act of modulating a bus/VCA fader based on the sidechain, and the resulting resource usage, should be identical for buses vs VCAs.