Improve handling of chroma interleave on PAL betamax

[oyvindln]

On PAL betamax, the chroma on each track is offset in frequency rather than rotating the phase like on VHS, 8mm and NTSC betamax. Currently this is handled by using the cafc function to detect carrier frequency on each frame but this is slow and the cafc has some issues even when used on other formats.

Might work better if we can run the carrier detection to determine which track/field number phase we are on like we do with chroma rotation and use the specified fixed carrier frequencies instead.

On a color bar sample I made on myh SL-F1 it also detects the same freq on each track for some reason causing the chroma to be messed up which doesn't happen on conventional output - not sure if it's an issue with the recording function on the vcr causing this or an edge case of the carrier detection.

May or may not be the cause of chroma problems on #92

[davidvankemenade]

Thanks for looking into this @oyvindln!