These 100hz,200hz TVs - are they not risking unsyncing sound?

[NeilF]

If my (noddy) understanding of the new TVs is correct, they basically interpolate between frames? So instead of playing 24 frames a second, they inject additional fill in frames between them.

But surely this means they are one frame beind the true one?

ie: The TV is sent frame 1, but the TV does not display frame 1 unti frame 2 is received, and so on... Now if the audio is being pushed out to an amp and getting played immediately, couldn't the audio be ahead of the images on the TV?

Or is this time delay so minute it's of no concern?

Or is my understanding of these TVs wrong?

 

[NeilF]

Nope, If every thing is running HDMI 1.3 It has audio sync as part of the specs.

Version 1.3

HDMI 1.3 was released June 22, 2006 and increased the single-link bandwidth to 340 MHz (10.2 Gbit/s. It optionally supports Deep Color, with 30-bit, 36-bit, and 48-bit xvYCC, sRGB, or YCbCr, compared to 24-bit sRGB or YCbCr in previous HDMI versions. It also optionally supports output of Dolby TrueHD and DTS-HD Master Audio streams for external decoding by AV receivers. It incorporates automatic audio syncing (audio video sync) capability. It defined cable Categories 1 and 2, with Category 1 cable being tested up to 74.25 MHz and Category 2 being tested up to 340 MHz. It also added the new Type C miniconnector for portable devices. HDMI 1.3a was released on November 10, 2006 and had Cable and Sink modifications for Type C, source termination recommendations, and removed undershoot and maximum rise/fall time limits It also changed CEC capacitance limits, clarified sRGB video quantization range, and CEC commands for timer control were brought back in an altered form, with audio control commands added. HDMI 1.3b was released on March 26, 2007 and added HDMI compliance testing revisions. HDMI 1.3b has no effect on HDMI features, functions, or performance, since the testing is for products based on the HDMI 1.3a specification. HDMI 1.3b1 was released on November 9, 2007 and added HDMI compliance testing revisions, which added testing requirements for the HDMI Type C miniconnector. HDMI 1.3b1 has no effect on HDMI features, functions, or performance, since the testing is for products based on the HDMI 1.3a specification. HDMI 1.3c was released on August 25, 2008 and added HDMI compliance testing revisions, which changed testing requirements for active HDMI cables. HDMI 1.3c has no effect on HDMI features, functions, or performance, since the testing is for products based on the HDMI 1.3a specification.

But, in my case, and a lot of peoples, I suspect the HDMI goes straight to a TV, and audio (via optical for example) goes to an amp?

For most people it's the simpler more friendly wiring solution...

 

[NeilF]

Its a valid question, and is the same reason I think these 'smoothing' technologys can introdcue lag in gaming. You need to a delay to allow the processing to work due to the reasons you have mention

However on the internal stuff I can only assume the TV corrects for the sound delay, ive never noticed any issues when using these 100hz modes on TVs i have had experience of

Cheers

Well, I'm not informed enough to know if my assumption of the process is correct. But if it is then the system has to be putting in a 1/25th of a second delay?

Now if anyone has audio going seperately to an amp, then would this 1/25th of a second delay actually be an issue? Can you see/notice a 1/25th of a second mis-match? I doubt it?

 

[NeilF]

Ahh i see what you mean now, Ive not noticed with my setup. However, i am only running HDMI. Its a good vaild question though.

Infact I don't see how HDMI changes the question.

Frame 1 goes out with audio for it... Followed by frame 2 and it's audio for it (OK I know they're not bound togethor like that, but for the sake of example let's assume that's the case)...

They go into your amp, and you amp plays the audio for frame 1 and passed the video to your TV... which... doesn't display it until it's received frame 2. Meanwhile your audio has now moved onto frame 2...

So the video is still lagging behind a frame?


So the fact you've not noticed anything, and assuming you have one of these 100hz/200hz sets, maybe this shows the delays is so small, there is no issue And I'm just wasting everyones time

 

[NeilF]

However, as i said before as i am runnig a complete HDMI 1.3 setup, i believe this should play a part in the audio sync problems. Ive not tryed any of the inputs via a optical / coax cable though.

Andy

But all your players/sources will do it push out video and audio togethor, be it down the same wire (HDMI) or split up (HDMI and optical). Your TV (we think) will then put in a 1/25th of a second delay on the video...

So the fact you're not seeing any sync issues suggests either we're miss understanding the techonology and this no video delay, or it's so tiny you just don't notice it... (My guess is the latter)

 

[NeilF]

I think your getting confused here.

The way I understand it is that it is displaying frame 1 twice, then frame 2 at the correct time, etc.

100hz has a period of 0.01 seconds, while 50hz is 0.02 seconds. So time between frames on a 50Hz TV is 0.02 seconds.

On a 100hz TV it's still 0.02 seconds but frame 1 has been displayed twice in that time. (0.01 seconds between updates)

From what I think you think it does means that the sound would get more and more out of sync, and as it doesn't its not how it works. (It would be one frame, then two frames then three frames behind and so on?)

Basically don't worry about it

Yes, but it could display 1000 generated images between the real frame 1 and the real frame 2, but it CANT do that until it's received frame 1 AND frame 2. So it is alway has to lag behind the signal/transmission by 1 frame.

Assume 24FPS, that means about 0.042 of a second...