How much lag in HDMI?

[Keatah]

Yup.. how much lag is there in an HDMI connection? Surely it isn't as fast as an analog RF, Composite, or S-Video connection. Those are near instant and the delay is only the time it takes to get through a series of transistors.

Edited May 27, 2015 by Keatah

[potatohead]

There is a frame at a minimum with HDMI. There may be more, depending on the TV video processor and how much buffer time it really needs. If your TV has a "game" mode, then that will be the minimum lag. Other modes may well include some advanced processing / noise removal that will do two things minimum:

 

1. Your display may not be pixel perfect due to smoothing, scaling, noise removal, color processing, etc...

 

2. Lag will increase.

 

Now, if you are using an older analog device, the display happens as the signal does on composite, RF, Component, S-video, RGB.

 

If you are using a newer device, those may well have the same minimum one frame lag, or quite a bit more depending on how the video signal gets processed into whatever data is useful for the display. This path could be longer than your HDMI path, again depending on the processor and a variety of other things. Is the display being scaled? Is the analog signal processed into a digital one, which then gets processed again?

Edited May 27, 2015 by potatohead

[Rybags]

The "i" modes mean at least a frame has to be buffered for merging with the next one.

 

The whole thing can be annoying. I got a sound bar which I have digital audio out from the TV going to and it doesn't even keep in sync with the TV's audio... though not directly relating to HDMI lag.

 

Some TVs have delay on the old analog inputs. Especially the later CRTs that do 100/120 Hz modes.

[fujidude]

Don't forget that with modern sets, even analog signals often have a significant amount of digital processing done to them before they are output for the user.

[kaufenpreis]

Every component has some lag factor in it. Light speed, despite being extremely wtf fast, is not instananous, especially through a medium (electricity traveling through insulated copper/gold/etc wiring).

That said, HDMI is actually has less latency than component or other cables due to it being a singular, high speed transmission line, as opposed to, well, seperate components. And unless you have either a very slow response time on your screen, or "pro gamer" reflexes, you'll probably never notice it.

[fujidude]

Oh yeah, and since signal processing is done in the digital domain these days, analog signals require the extra step of first being converted to digital before processing. HDMI signals are already in the digital domain before processing begins.

[Rybags]

Analog requires buffering for similar reason to "i" modes of digital - only the progressive modes using component can be shown straight up, the 576i/480i mode that reflects the old analog TV standards requires blending current/previous frames.