Reply To: Advanced timing settings for Amiga

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#10072
jarp
Participant

Huh, I think I finally fully understood how advanced timing settings do work and what each setting does. So I was able to dial in settings based on knowledge instead of trial and errors (resulting settings are more or less the same though). So here are definitive settings working on my Amiga 600 for PAL modes when using OSSC’s lineX2 mode:

PAL:HiRes, PAL:LowRes:
240p/288p lineX3: Off
H. samplerate: 908
H. synclen: 60
H. active: 724
V. active: 288
H. backporch: 77
V. backporch: 24
Sampling phase: Adjust until you get stable and crisp picture

Explanation: Amiga’s minimum resolution for PAL is 640×256 and resolution when utilizing overscan is 724×283. Using checkerboard pattern it seems H. samplerate 908 is pixel perfect setting. H. active 724 allows capturing everything Amiga outputs. V. active 288 is actually more than Amiga outputs (283), however 288 is PAL standard and may sync better than 283. As a added bonus 5 x 288 = 1440 which allows pixel perfect scaling on 1440p displays (if your display does not manage to mess it up like mine does, waiting for 5x mode…)! Backporch settings just centers the picture, adjust if yours requires different values, not sure if this depends on Amiga.

If you want to use lineX3 mode, just double H. sample rate and H. active and adjust H. backporch. Oh this allows also capturing Super-HiRes resolution (min. 1280×256 max. 1440×283) properly, lineX2 modes does not output high enough resolution for that.

PAL:HiRes, PAL:LowRes, PAL:Super-HiRes:
240p/288p lineX3: On
H. samplerate: 1816
H. synclen: 72
H. active: 1448
V. active: 288
H. backporch: 198
V. backporch: 24
Sampling phase: Adjust until you get stable and crisp picture

Super-HiRes outputs only 1440 pixels so you could reduce H. active to 1440 for it, but then you would have to re-adjust for LoRes and HiRes modes. Best to leave it to 1448 and it’s compatible with all modes.