ZX Spectrum Next Core and Native YC Output

[bricabrac]

Hello,

Can anyone confirm if Y/C has been added to the official core? I am testing the version from the Distribution_Mister, i.e. ZXNext_20230301.rbf alongside the active Y/C adapter and although I get colour picture, the issue is the chroma i like "behind" the luma by 1 attribute block. What I mean by that is there is a "ghosting" image on the screen, shifted to the left by 8 pixels, which is clearly a chroma part of the video signal.

This issue is so obvious that I don't think anyone wouldn't notice it when implementing and testing the feature in the core so I started to think that mayby it hasn't been implemented yet. But on the other hand I should not see any colours out of the core if it wasn't implemented at all.

Has someone observed such issue? Can this be a problem with my setup or rather a bug in the core?

Many thanks.

[bricabrac]

I will answer to myself in case someone is interested.

I confirm YC output has been implemented in ZX Next core and can produce great tresults if configured properly.

The problem is phase accumulator value defined in yc.txt is only good for refresh rates 48.8Hz (Pentagon) and 50.1Hz (ZX Spectrum 48K). It appears the 49.4Hz generated by ZX Spectrum 128/+2/+3 requires different value of phase accumulator othervise it produces crazy artifacts I described in previous post. Unfortunatelly I wasn't able to find the right value :/

On a side not, the exact same issue is present in ZX Spectrum core.