Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[6233638]

I have been meaning to purchase a DAC/headphone amplifier for a long time now but analysis paralysis had set in, and I always ended up putting it off.
Well I think I have maybe made a decision, but one issue remains: lip sync.

I am currently running video from my PC to the TV via HDMI, and using the headphone output from that. (with extensions)
Because it's running through the TV, any processing delays are automatically corrected.

However all flat panels have some amount of latency inherent to them, and my TV has about 30ms - in PC mode.
When watching videos fullscreen, I put it into Video mode (there's a toggle on the remote) which increases latency to somewhere in the region of 90-120ms.

While this latency still presents a problem outside of Media Center (unless Windows has some global adjustment I have overlooked) I find that I am really only running audio through it now, and there's always the loopback feature. (though I don't know how successful that will be)


Would it be possible to have separate adjustments so that I have 30ms when I'm using the desktop and playing back a video in a window, then have it change to ~120ms when I play it back fullscreen?

[6233638]

Bumping this while Matt is around.

[Matt]

You could use two different zones (and maybe ZoneSwitch) each with independent settings depending on how you're playing.

It might require a little manual setup, but that's probably reasonable considering it's a pretty specialized use-case.

[6233638]

Any suggestions on what I need to do to have ZoneSwitch change depending on whether the video is being displayed fullscreen or not?

[glynor]

Any suggestions on what I need to do to have ZoneSwitch change depending on whether the video is being displayed fullscreen or not?

Yeah, I don't think you can.

How do you switch the mode on your TV?  Is it literally with the TV's remote, or is it blasted by a UIRT and something like EventGhost/Girder/AutoHotKey?  If the latter, you could script MC to change zones as part of the same button-push.

[6233638]

TV remote - that's why I was hoping the team might consider adding LibCEC support.

[alyupb]

However all flat panels have some amount of latency inherent to them, and my TV has about 30ms - in PC mode.
When watching videos fullscreen, I put it into Video mode (there's a toggle on the remote) which increases latency to somewhere in the region of 90-120ms.

May I ask how you determine the amount of latency?

[6233638]

May I ask how you determine the amount of latency?

RMAA has the ability to measure the latency of a loopback connection through your soundcard. (Line out > Line in)

So that might be 8ms.

If I then run line out through my TV and back into the sound card, subtracting 8ms, I have the exact delay the TV is using, and can measure the difference when I switch between PC and Video modes.

[6233638]

Well, my DAC arrived, and as I thought, latency is a big issue.

Unfortunately I didn't have the cables I need to measure this accurately - my analog cables weren't long enough, and it seems my TV will not accept an external audio input if an HDMI connection is used for the PC - only DVI, and I don't have a 15ft DVI cable, or plan on running one through the walls just for this.

I was able to measure the loopback latency (53ms with the standard Windows 8 driver - this drops a lot if you install the Realtek drivers) and running audio through HDMI into the TV, then out through the line-out which measures 73ms in game/pc mode (20ms latency) and 138ms in film mode (85ms latency)
But these results assume the output latency is the same over HDMI and the on-board sound, which is likely not the case, and I only had the time to test 60Hz.

To keep things simple, I will upsample all videos to 192kHz where the DAC has 0.47ms latency.
The ASIO buffer is set to 2048 frames by default though, and I haven't changed it - I think that is about 10.5ms at 192kHz?

So overall I should be somewhere in the region of 74ms when playing back films fullscreen, and 8ms when playing back videos windowed. (which is done in PC mode) The 65ms gap between the two is very noticeable.


And in general, trying to adjust latency for perfect audio sync seems to be a complete nightmare. I wish there was some easier way of doing it.
I tried one of those Leo Bodnar Lag Testers when they were released, but that only measures display latency and doesn't account for the audio device. (and the software using it)
Even with this method of determining latency, which is probably not entirely accurate in my case, is really complicated. I haven't spent too much time with it yet, but it seems like 73ms might be about right, but is still a bit off.

Considering no displays aside from gaming monitors and CRTs effectively have zero latency, and the output from the sound card/DAC etc. is variable, I'm surprised more people aren't having lipsync issues.
Is everyone just running HDMI into a receiver these days? (HDMI 1.3 devices support automatic lip-sync correction)

The other alternative is running a 15ft optical cable through the walls (if that's even possible?) into the TV, and then running that into my DAC. But the TV is limited to a maximum of 24/48, and I don't know whether it correct for those delays via optical or if it's just the analog outputs.