Tip for anybody having low lag syncing problems on the LCD TV

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Chris23235
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Tip for anybody having low lag syncing problems on the LCD TV

Postby Chris23235 » Wed Jan 15, 2020 10:54 pm

I use my MiSTer on a Samsung Full HD LCD TV via HDMI. Vsync_adjust=1 works fine in all 60 Hz cores and scrolling is butter smooth with low lag, but on all cores where I use 50Hz PAL (e.g. Amiga, C64) it doesn't sync, so I had either use vsync_adjust=2 which results in stuttering in fast scrolling games (e.g. Uridium) or try to run the games in NTSC mode which is not compatible with many PAL games.

I just found out, that vsync_adjust=1 syncs, when I run the MiSTer in 1280x720@60Hz. The downside it, that it is not the native resolution of the display, which dimishes the image quality, but to me that's much better then stuttering scrolling.

If you have problems getting vsync_adjust=1 to work properly on your LCD TV try it at a lower resolution, this might help.

You can set the resolution per core, so that you don't have to run all cores in the "wrong" resolution.

paulbnl
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Re: Tip for anybody having low lag syncing problems on the LCD TV

Postby paulbnl » Wed Jan 15, 2020 11:10 pm

For 50Hz you have to use the PAL override 'video_mode_pal=9' for 1080p50.

Chris23235
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Re: Tip for anybody having low lag syncing problems on the LCD TV

Postby Chris23235 » Thu Jan 16, 2020 12:21 am

I already tried this, the result is, that my TV is constantly loosing sync. Especially in the minimig core with its ever changing resolution, the screen stays black for several seconds some times. With 1280x720 everything works fine. I guess it's because I use a TV instead of a monitor, these devices don't have to be very flexible when it comes to different resolutions and frequencies.

A correction to my previous post: I meant vsync_adjust=2. With the value 1 everything works, but it stutters as it is expected to happen.

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Re: Tip for anybody having low lag syncing problems on the LCD TV

Postby Sorgelig » Thu Jan 16, 2020 2:06 am

With vsync_adjust=1 it should not stutter. If vsync_adjust=1 stutters then it means your TV doesn't sync with input refresh. It's unusual for most TV to do a sync as it's mostly monitor feature.

Chris23235
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Re: Tip for anybody having low lag syncing problems on the LCD TV

Postby Chris23235 » Thu Jan 16, 2020 6:56 am

I see, that's what I originally thought, but then I tried vsync=2 on 1280x720 and it worked and I thought I got things wrong and vsync=1 is expected to stutter. Do you know if it is common amongst LCD TVs to sync in other resolutions they don't sync in the original resolution? I didn't knew LCD panels where sensitive to resolutions at all.

I use the HDMI port that is meant for PC use and that disables picture "enhancements" by the TV, so I guess the TV switches to some kind of monitor mode. In 1920x1080 it sometimes syncs in low lag mode after a few tries, but for the minimig core this becomes tiresome. In 1280x720 there are no problems.

I am happy as it is, because I didn't expected the 50 Hz cores to run without stutters at all (for these cores I have a Commodore 1081 monitor, that I currently use with my MiST device).

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Re: Tip for anybody having low lag syncing problems on the LCD TV

Postby Sorgelig » Thu Jan 16, 2020 7:51 am

In most cases TV (and even many monitors) have fixed 60Hz refresh rate and it's never changing. So stuttering will be always present on such TV. And stuttering even more visible when input refresh is close to 60Hz. For example 50Hz stuttering on fixed 60Hz TV is less noticeable.

Chris23235
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Re: Tip for anybody having low lag syncing problems on the LCD TV

Postby Chris23235 » Thu Jan 16, 2020 4:57 pm

Many thanks for the explanation, I think now I got it, didn't thought about the difference between display refresh rate and input refresh rate.

What I still not get is, why vsync_adjust=2 works, while vsync_adjust=1 fails. As far as I understand the difference between both modes is, that vsync_adjust=2 didn't use any framebuffer. It seems the TV sees the lack of a framebuffer as a signal to try to do a sync. As doing a sync is more of a feature of Monitors than of TVs, it seems that the TV interprets the lack of a framebuffer as a signal to switch into some kind of monitor mode.

Strange, but as it works, I am happy the way it is.


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