Speed Is the Killer Feature

Re:Speed Is the Killer Feature by mrob on Tuesday March 02, 2021 @01:21PM (#26318488)

DP does not require buffering the entire frame. Data is sent as "micro packets". Each micro packet may include a maximum of 64 link symbols, and each link symbol is made up of 8 bits encoded as 8b/10b. The slowest supported link symbol clock is 1.62Gb/s, so even considering protocol overhead there are always millions of micro packets per second.

If the required video data rate is lower than the link symbol rate the micro packets are stuffed with dummy data to make up the difference, and up to four micro packets may be sent in parallel over separate lanes, so some buffering is required, but this need only add a few microseconds of latency, which is not perceptible. Of course it's possible for bad implementations to add more, but the protocol was designed to support low latency.

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Re:Speed Is the Killer Feature by fxtentacle on Tuesday March 02, 2021 @02:54PM (#26319719)

Thank you for teaching me something new :) I didn't know about micro-packets before.

In that case, I'm guessing the latency is coming from the fact that most LCD screens are caching one full image so that they can re-scale it in case the incoming video resolution isn't identical with the display's native resolution.

I vaguely remember there being an experimental NVIDIA feature to force scaling onto the GPU in hopes of reducing lag, but not sure that ever got released.

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