Audio vs video latency in TVs?

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dclon
Posts: 30
Joined: 12 Oct 2014, 08:50

Audio vs video latency in TVs?

Post by dclon » 28 Feb 2015, 14:27

It's occurred to me that TVs probably keep the audio in sync with the video, and measuring audio latency seems simple, so it can be used to indirectly measure the video latency.

The latency figures reported on the internet for my TV, measured with Bodnar's tester, are around 15ms (probably an average of top/mid/bottom of frame). Measuring TV audio latency delta, above the delta for speakers/headphones connected directly to the computer, I'm getting 45ms. Even if we assume that the TV syncs the audio to the end of the frame it's 20-25ms off. For whatever it's worth, the TV audio latency is the same at 60Hz and 24Hz.

Can anyone think of a reason for that? I'm using the fastest TV input mode. Maybe more latency is introduced in the Windows audio pipline when using HDMI sound rather than the directly connected speakers/headphones?

dclon
Posts: 30
Joined: 12 Oct 2014, 08:50

Re: Audio vs video latency in TVs?

Post by dclon » 01 Mar 2015, 13:05

I tried with another computer. Different brand of graphics, different OS. Direct audio vs HDMI delta: 20-21ms. Closer to the expected 15ms for the TV. I wonder if there's a way to figure out the HDMI out delta on the computer. Another confounding factor that could exist is the relative sync between the drivers for the microphone interface and the HDMI audio out.

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