Probably Sadly Uninformed Video Display Concept - No Refresh Rate

Discussion in 'General Hardware' started by Size_Mick, Feb 25, 2018.

  1. Size_Mick

    Size_Mick Master Guru

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    I can understand why CRTs need one. I think I understand why LCDs have one. LCDs have one because everything before them was made for display on a CRT, right?

    I realize that everything I say here could be talking out of my a$$, and this may not even be the right place to talk about this, but it's something that's been on my mind for awhile. Feel free to school me if you've got the knowledge to refute anything about this concept.

    Can't we get rid of the refresh rate / scan-line concept, and just have every pixel on a display change only when it's supposed to? So if it's red, it's always red until it's told to be blue or off or whatever. And instead of doing it a line at a time, can't we just do it to individual pixels anywhere on the screen at any time? I realize that this wouldn't necessarily work with existing graphics technologies. Maybe something built from the ground up could accomplish this, though, eventually.

    We already compress video in a way that's analogous, I think: Each frame is compared to the last and only the changes are recorded. So in this concept, the "refresh rate" would be determined solely by A) the speed with which the hardware doing the rendering can deliver frames (which could perhaps have only the information that's different from the previous frame), and B) the rate at which the display's pixels can switch. But I don't see why, on a modern display, you would need to do it one scan line at a time. I assume this is totally due to backward compatibility.

    Anyone care to add something? Thanks for reading.
     
    Last edited: Feb 25, 2018
  2. AsiJu

    AsiJu Ancient Guru

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    I'm not an expert on displays, but interesting idea at the very least. Why not? As a concept.

    Though even if displays would refresh on demand, on a pixel basis only, I suppose we'd still need some form of refresh rate or "pixel polling rate" to check if any pixels are outdated.
    Plus if using per-pixel refresh instead of scan-lines, then you'd need a "relay" for each pixel to dictate if it's red , green, blue, off.

    Internal electronics of a display would need to be quite a bit more complicated I think.
     
  3. Chester1994

    Chester1994 New Member

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    More than backwards compatibility, it´s been there because it has proven effective. I completely understand the point of what you talk about, but I can´t find a real use for this where it´s going to boost FPS or help.

    For "broken" frames, we have V sync, G sync, Free sync, etc.

    Also the frames are neccesary to be FRAMES and not just "let´s color this and leave that how it is" because they are used for other purposes and in certain algorythms (depth of field, T-AA)

    Remember that GPUs are extremely efficient in doing parallel calcs. For example, throwing a frame as soon as it was rendered. In fact, they were created with the purpose of transforming and rendering pixels.
     
  4. Size_Mick

    Size_Mick Master Guru

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    You're probably right. Still, I can't help but wonder if it would be more efficient to swap out just the changed pixels at an instant than scanning it a line at a time. If there has to be a lot of work on the hardware side to render the complete picture a complete frame at a time, could there be some extra hardware thrown on at the end that compares the next frame to the last and only sends the changes to the display? I don't know that there would be any benefit in terms of power reduction on the rendering side, but certainly it would require less data to pass to the display, wouldn't it? Maybe that would allow a more detailed picture for the same amount of bandwidth, which might have some practical benefit. Also you'd probably never have to worry about displays being out of sync with movie cameras again :p

    Maybe if they combined this idea with e-paper it could be useful, I don't know.

    What's the highest refresh rate that's been achieved on a display?
     

  5. haz_mat

    haz_mat Master Guru

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    An implementation like that would present other challenges - such as addressing each pixel and how to handle scenarios where the most/all of the frame is to be updated. I figure you'd need at least an additional 12 bits for each axis on each pixel to describe its location - and that only gets you up to 4096x4096. Color data already takes up the usual 24bits/px, addressing like this would double that - so anything more than half of the frame getting updated would use more bandwidth than just updating the entire frame.

    Present signalling methods only depend on the total number of pixels and the refresh rate. The data rate is quite high, but this isn't much of a problem considering the typically short distance to send the signal. The fire-and-forget method of sending data to the monitor is still holding its own just fine - keep it simple, right?
     

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