What's vertical sync rate derived from in WinUAE?

[Gaula92]

Hello there,

I've noticed that, to get perfectly synchronized screen refresh when emulating a NTSC Amiga in Amiberry 6.x sources ("preview" branch), which are based on the latest WinUAE, I need to set a physical video mode of exactly 59.940059 Hz.

In other words, using a 60.000000 Hz mode results on small hiccups every 10-20 seconds due to the small discrepancy between the emulated Amina NTSC system vertical sync rate and the physical host refresh rate.

I know it's a well known NTSC vertical sync rate (apparently derived from 60*1000/1001, where 1001 was historically chosen to ajust the vertical syn freq down to create an space needed for the color signal without interfering the audio signal), but where are those ~59.94 Hz derived from in the WinUAE sources?

Also, would it be possible to sync to host refresh instead? Having a 59.94 Hz video mode automatically set on modern displays isn't that common...

Thanks!

[TCD]

I would guess from this: https://en.wikipedia.org/wiki/NTSC#R...d_refresh_rate

This, as mentioned, is how the NTSC field refresh frequency worked in the original black-and-white system; when color was added to the system, however, the refresh frequency was shifted slightly downward by 0.1%, to approximately 59.94 Hz, to eliminate stationary dot patterns in the difference frequency between the sound and color carriers (as explained below in § Color encoding).

[Toni Wilen]

Tick Display panel Settings area bottom right checkbox and then fill the text box with refresh rate you want. This keeps the rate static.

Amiga refresh rate normally depends on mode: interlaced is 50/60Hz, non-lace is slightly less (long field). or slightly more (short field).

[Gaula92]

Originally Posted by Toni Wilen

Tick Display panel Settings area bottom right checkbox and then fill the text box with refresh rate you want. This keeps the rate static.

Amiga refresh rate normally depends on mode: interlaced is 50/60Hz, non-lace is slightly less (long field). or slightly more (short field).

Ah, yes! I adjusted to my monitor in-use exact refresh rate using that and it works.
But the problem with that is that the number of generated audio samples isn't adjusted, so for example if a game runs at 59.xxxx Hz and I adjust the frame rate to 60.000000 Hz, too few samples are generated and the audio occasionally "skips". Totally expected.


So... Is there an option for number-of-audio-samples compensation for framerate adjustment?
That would allow perfect audio and video synchronization at last.

[malko]

Originally Posted by TCD

I would guess from this: https://en.wikipedia.org/wiki/NTSC#R...d_refresh_rate

Looks like we have the same readings

Edit : NTSC : Never Twice the Same Colour.