About latency on the OSSC Pro

[Massot]

I already sent this question through the “contact us” form yesterday because I could not log into the forum. My apologies for repeating it here.

I have already received my OSSC Pro and would like to ask about the latency of the device: it is widely reported to be 1/2 frames in scaler mode -depending on the actual scaling configuration-, does this mean a flat 16/33ms -1/2 frames at 60hz- or is it always 1/2 frames of the output framerate? Say, if I set the device to “framelock off” mode and activate the “2x framelock” option -final picture at 120hz- will my latency be 16/33ms -comparable to 1/2 frames at 60hz- or will it actually be 8/16ms -actual 1/2 frames at 120hz-? The second option is very attractive and, at 8ms, the latency would be unnoticeable while being able to take advantage of the scaler mode with little to none of the downsides.

Additionally, is it possible, within the current firmware, to activate the mode listed abode -“framelock off”, 2X framelock- while also enabling the VRR and HDR flags at the same time? I vaguely recall that there was a conflict when activating VRR and HDR at the same time. HDR is not crucial to me, since I don’t always use scanline effects and rarely need the brightness boost, but being able to activate a hypothetical 120hz output -framelock off (60hz), 2X mode- with VRR to take advantage of the higher response of my monitor while being able to handle instant resolution changes at 8ms/16ms would be fantastic. My guess is that if this hypothetical is possible, that it would only work at 1080p and 2K, which is not an issue for me.

I currently cannot fully test whether this is working because my current setup requires me to split my HDMI at either a 1080p60fps capture card or at a similarly performing HDMI splitter, neither of which support VRR or HDR, hence why I’m asking. If the scenario above is possible, I’d upgrade my setup with a higher quality capture device.

[marqs]

On Scaler mode with 1x framelock, the latency should be a bit over 1 frame. With 2x framelock, average latency should drop to 0.75 input frames since top of the initial output frame still has 1 frame latency while bottom has 0.5.

With framelock off, there is an adder of 0-1 input frames and it fluctuates between that as there is no lock.

There shouldn’t be conflict of using HDR and VRR together, but keep in mind that VRR only sets the flag in metadata and does not vary vertical blanking, thus it’s currently more of a compatibility option.

[Massot]

Thanks for the asnwer.

Shoulnd’t the VRR flag still be helpful for framerates slightly below and slightly above 60hz in order to avoid the occasional judder? That was my expection since this is an external form of VRR which cannot really read in-game performance.

So, as I am understanding:

• For the lowest latency on games with frequent resolution changes: scaler mode on and framelock “off”. However, should I set the option to “framelock off (120hz)” or should I set it to “framelock off (60hz)” and then set the mode in the previous menu to “2x”? Is this even possible?
• For the lowest latency on games which would be best enjoyed by transforming the image (Super Game Boy, Game Boy Player and other modified hand-held systems with video output mods): scaler mode on with the necessary zoom that each system requires, framelock “on” and “2x” mode enabled.

I completely forgot to mention that I am playing on a 240z screen which does support VRR and HDR.

[BuckoA51]

In my tests yes adding the VRR flag can help with framerates that deviate from the 59.94 NTSC spec, for example it allowed for smooth scrolling on a PAL Amiga forced to 60hz (which ends up at 59.2 something maybe, quite a bit out). This was on an LG C9 OLED.

I would think frame lock off 120hz wouldn’t work to your advantage if you are trying to minimize lag though I could be wrong. So much depends on  your TV too. You could always purchase a Time Sleuth from us for further testing 🙂

[Massot]

I will check reviews and usage guides for the Time Sleuth. I’ve heard about it for years and never considered getting one myself. I just got a new capture card, so the Time Sleuth could be interesting as well.

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