Does chaining HDMI signals via my amp result in input lag?

[Sumez]

So for the setup I've been using since I got my new "game room" earlier this year I've been hooking up my my amplifier using a regular optical toslink cable from the TV to the amp. That works great for signals coming directly from the TV, and for mono/stereo sound coming from any of my old school consoles it's obviously more than adequate.

But I've found that the standard (LPCM?) used by at least my WiiU and Switch is unable to use all 5 sound channels for surround sound when transfered via toslink, so to make it work it seems that I need to hook it up with the HDMI cable chained via the amp, which of course had a HDMI output back to the TV.
So for the purpose of playing video games, this leads to a pretty simple question that I fear might not have a simple answer - the potential for added lag.

Looking around the internet you mostly get the typical "well I don't notice any input lag" reports, which are pretty much useless to me. Input lag can be such a vague concept that I wouldn't trust my own observations either, and would love a more technical conclusion if possible.

From what I can tell, it can be either way. Obviously if the amp is doing any kind of processing of the image there's gonna be a tiny bit of lag, but apparently it's possible for it to just pass on the output directly, while picking up the audio signal.
So is there any way for me to know with certainty what my amp is doing? It's a 7.1 Sony Surround receiver that I bought probably ~10 years ago, and I know it at least has the option of outputting some kind of OSD picture via HDMI to supplement the alphanumeric LCD display on the amp itself. Are there any typical settings I should look for in the menu to turn off, or can I assume there shouldn't be any lag issues out of the bag?

I'm not a big audio geek and don't really know a lot about these things, and really prefer them to just work on their own. But if a game has even a single frame of lag more than "it needs", I feel like most of my current setup would have been in vain.

[Unseen]

Input lag can be such a vague concept that I wouldn't trust my own observations either, and would love a more technical conclusion if possible.

Then your only option is to measure it yourself or find a result from someone that has measured the exact model of AVR you use and has described the measurement setup in enough detail for you to trust that result.

From what I can tell, it can be either way. Obviously if the amp is doing any kind of processing of the image there's gonna be a tiny bit of lag, but apparently it's possible for it to just pass on the output directly, while picking up the audio signal.

Even with no video processing your amp will need to decode/reencode the HDMI signal because it needs to be able to handle HDCP for DRMed sources, so there will always be a tiny bit of lag no matter what it does. It is possible to implement this in a way that does not introduce humanly-noticable lag even if you did it a dozen times in a row.(*)

It's a 7.1 Sony Surround receiver that I bought probably ~10 years ago, and I know it at least has the option of outputting some kind of OSD picture via HDMI to supplement the alphanumeric LCD display on the amp itself. Are there any typical settings I should look for in the menu to turn off, or can I assume there shouldn't be any lag issues out of the bag?

You'll have to measure that yourself or find results from someone who has measured it. An OSD can be implemented as a real-time overlay that does not add noticable lag or it could be implemented by storing the entire incoming video frame in a frame buffer, painting on that and scanning it out later, which would introduce at least one frame of lag. If your AVR has additional video processing features like a scaler, disabling them might reduce lag, although pure scaling (but not high-quality deinterlacing) can also be implemented in an almost lag-free way because it does not need information from past or future frames.

(*) If I gave an estimate in pixels or lines, there would almost certainly some person misreading it as frames instead, so I'm not giving any numbers. =) It has happened before, "a few dozen pixels" of lag in GCVideo I mentioned in a forum post somewhere became "GCVideo is unplayable, it has 12 frames of lag!" in some Smash-related discussion elsewhere.

[Konsolkongen]

If you have an OSSC you can build this to check lag:
http://junkerhq.net/xrgb/index.php?titl ... ncy_tester

I've used that myself to confirm that my previous Yamaha RX-A1010 and now RX-A2080 were indeed lagfree with video processing turned off.

[neorichieb1971]

When I daisy chain through my amp I don't notice anything different.

However, for some reason it takes 5+ seconds for my TV to recognize the chain has an active signal.

Probably not important to you. But the VR equipment for the PS4 did not register a signal at all through my amp.

And eArc set on my TV seems to want to govern everything. Not sure why as I turn it off on the TV but the next time I switch something on I don't get a signal because eArc has turned on again.