Channel mapping implementation regarding gain normalization

[KaoDome]

Hi, I'm evaluating dBPa to handle channel downmixing. I was surprised not to see any preset for say 5.1 to stereo (unless using the channel count DSP does it automatically), but since there is a channel mapper it's possible to choose what goes into the mix and the proportions.

I'd like to know if the audio is renormalized though. For example, say we're going from 5.1 (side) to 2.0 using the following:

Left = 100% Front Center + 30% Front Left + 30% Side Left
Right = 100% Front Center + 30% Front Right + 30% Side Right

Are the gains renormalized internally so that the total is 1, avoiding potential clipping noise? (in ffmpeg terms, it'd be like using < in the channel specification instead of =)

Or should we be using the volume normalize DSP? I'm guessing if we were to use the volume normalization DSP as well order matters and it should be after the channel mapping one. I'd be lost if DRC were added to the mix though, no idea where it should be.

[Spoon]

Re: Channel mapping implementation regarding gain normalization

No, you would use the Bit Depth first to Floating Point, then do a normalization after channel map, final step is to 16 or 24 bit.