Line by Line Display vs Frame Display

[Fresh]

I read about Sample and Hold Displays (LCD/OLED) vs Impulse Displays (CRT/Plasma) and software techniques on here to have sample and hold displays emulate impulse given a high enough refresh rate (CRT Beam Filter).

Can’t manufactures combine the best of both worlds. (If any are reading this forum)

HDMI Display data is transferred line by line (HSYNC) until it fills the frame buffer (VSYNC). Once the frame buffer is full, Sample and hold displays then display the frame buffer for a full frame.

Can’t displays excite the pixels line by line as HSYNC data pipes in.

Or if not create a few frame buffers that will store a partial frame. Eg. Divide the screen into 4 vertical section (or more 8, 16, so on based on testing with panel characteristics). As HSync fills up the a partial vertical frame buffer. Sample and hold that vertical portion of the screen until the next one is completed.

This way a whole frame wouldn’t have to be piped into a post processing shader / filter. And it would work with whatever input Hz is supported by the display natively.

I honestly thought that’s what the “Line Buffer Input Lag Reduction” on the older LG OLED C series game mode was doing but after getting an OLED i guess not. Motion is worse than CRT/Plasma.

[Chief Blur Buster]

Can’t manufactures combine the best of both worlds. (If any are reading this forum)

Laws of physics.

You can't have infinite bandwidth. A 3840x2160 at 24bits (3 bytes per pixel) image would be 3840x2160x3 = Over 24 megabytes. At 240Hz, a 4K240 display is trying to display 24 million pixels in 1/240sec. You're displaying 240 images per second at 240Hz.

(You can do compression (e.g. DSC), but that's also a rabbit hole I'll bypass temporarily for the purposes of this post)

- How do you transmit 24 megabytes in 1/240sec? That's faster than your optical fiber connection.
- How do the chips inside a display display the whole picture in 1/240sec? That's supercomputer-league fast.

It just isn't possible without going faster than light...
Our displays are literally running mini-supercomputers at this juncture.
And they are trying to keep it cheap (3 figure prices or low 4 figure prices). So it's very cutthroat of compromises.

You can buffer the image -- but buffering adds input lag. The best displays streams from the cable (top-to-bottom frame delivery) to the panel (top-to-bottom refresh) = latency of less than one refresh cycle. That's what most gaming monitors do nowadays; raster beamraced rolling-window scanout...

[Chief Blur Buster]

I honestly thought that’s what the “Line Buffer Input Lag Reduction” on the older LG OLED C series game mode was doing but after getting an OLED i guess not. Motion is worse than CRT/Plasma.

Latency does not necessarily have anything to do with motion.

You can have good latency but bad motion.
You can have bad latency but good motion.

It's not the same engineering. Latency can simply be a tape-delay style behavior (by the milliseconds) caused by a processing delay and/or buffering delay.

[Fresh]

Can’t manufactures combine the best of both worlds. (If any are reading this forum)

Laws of physics.

You can't have infinite bandwidth. A 3840x2160 at 24bits (3 bytes per pixel) image would be 3840x2160x3 = Over 24 megabytes. At 240Hz, a 4K240 display is trying to display 24 million pixels in 1/240sec. You're displaying 240 images per second at 240Hz.

(You can do compression (e.g. DSC), but that's also a rabbit hole I'll bypass temporarily for the purposes of this post)

- How do you transmit 24 megabytes in 1/240sec? That's faster than your optical fiber connection.
- How do the chips inside a display display the whole picture in 1/240sec? That's supercomputer-league fast.

It just isn't possible without going faster than light...
Our displays are literally running mini-supercomputers at this juncture.
And they are trying to keep it cheap (3 figure prices or low 4 figure prices). So it's very cutthroat of compromises.

You can buffer the image -- but buffering adds input lag. The best displays streams from the cable (top-to-bottom frame delivery) to the panel (top-to-bottom refresh) = latency of less than one refresh cycle. That's what most gaming monitors do nowadays; raster beamraced rolling-window scanout...

Since HDMI is uncompressed. You do not have to wait for the whole frame to be transferred and then flip the pixels at once. See info graphic.

displaymodule dot com/blogs/knowledge/introduction-to-hdmi-protocol

It is entirely possible to flip the pixels line by line as the data comes in (similar to the analog signal in CRTs)

What i meant by dividing the screen into 4 buffers you wouldn’t take a 60hz signal and send it at 240hz

Signal comes in (t=0ms) -> start

540 HYSC signals come in (t=4.16ms) -> top quarter screen is filled

Another 540 HYSC signals come in (t=8.32ms) -> top mid quarter screen is filled

Another 540 HYSC signals come in (t=12.5ms) -> bottom mid quarter screen is filled

Another 540 HYSC signals come in (t=16.6ms) -> bottom quarter screen is filled

they could do it line by line. or subdivide it however they like.

[Chief Blur Buster]

It is entirely possible to flip the pixels line by line as the data comes in (similar to the analog signal in CRTs)

That's correct, and that's what many LCD/OLED displays already do (high speed videos).

What i meant by dividing the screen into 4 buffers you wouldn’t take a 60hz signal and send it at 240hz

Some elements are done behind the scenes:

- There are a lot of methods of parallelizations being done such as subdividing the screens into multiple scanout zones (vertical strips), and having different electronics refresh those sections. The raster scanout is still at the same position on the same subdivided screen, so it looks seamless (single horizontal scanout line in same position, since it's a seamless version of all vertical strips).
- Accelerated display of 60Hz is already achievable via "Quick Frame Transport" tricks. Also, VRR also has this built in, e.g. display a 60fps frame in 1/480sec for a 480Hz VRR display.