I finally figured this one out. I got a RetroTink 2X, which is known to add essentially no lag, in hopes of playing my consoles on my Vizio D50-D1. But I was still getting severe audio lag and nothing I did seemed to change it -- no setting made the slightest difference, and changing HDMI ports changed nothing. (I used a Sega Nomad to hear the audio delay between the Nomad's built-in speaker and the Vizio's speaker.)
I was tearing my hair out, until this post made everything clear. It turns out that my TV does indeed have very low input lag over HDMI (~26.2ms), but has much higher audio lag (~86ms) that remains more or less constant regardless of the input source.
I'd been using the audio lag to estimate the input lag, and I hadn't imagined that any TV designer would allow for a 60ms differential between audio and video, let alone build a sync issue like that into the hardware -- but that's exactly the case here.
In any event, the solution was easy: run the audio directly from my AV switch into my stereo system, bypassing the RetroTink (and HDMI), and only use the HDMI to pass video. Problem solved: nice, crisp, low-lag gaming on my HDTV, with audio and video in sync (or at least within two frames). I still need to get some S-VHS or component cables to get a better picture than composite is giving me, but it's more than adequate for now.
BTW my signal chain before involved a lot of variables -- running HDMI from a Mac laptop via a mini-DP > HDMI adapter, for example, or running VGA from my Dreamcast into a VGA > HDMI adapter. At any stage of those things, additional lag could and did creep in (the Dreamcast setup had severe and unmistakable input lag).
I tried doing some audio recordings with Audacity to compare how those sources compared when running on other displays, but I didn't have a single, trusted, zero-lag source as a baseline until I got the RetroTink 2X.
- newtmonkey likes this