Optical cable sound delay

wizzywig27

Hi all

I am having troubles with my optical cable. I am running it from my Sony HD TV to my soundplate (LG with the Bluray player built in)...

There is a sound delay no matter what I play through it (SKY, Xbox, BT box etc), however there isnt one when playing DVD's through the soundplate.

I have checked all systems and there is no sound delay in system preferences.

Does anyone have any idea what the problem could be? Is it because its a cheap Tesco optical cable?

kwikbreaks

Optical cables are just fibre - no electronics in them at all so there is no way that the cable itself can introduce a delay other than speed of light although obviously the electronics at either end of it in the devices you are coupling could be to blame.

Sorry I can't suggest a solution.

boliston

My OH was noticing a lip sync problem today on sky and there was an option in the sky box menu to add some delay - i think she went with 40ms to fix it

RobTang

The thing is for secondary devices eg Sky, xbox etc. You are not supposed to route the sound through the TV. ie it should always be; Device -> Soundplate -> TV


The HDMI spec says the TV is not allowed to just do a straight pass through of the audio to a different medium (eg optical) it has to re-encode the audio and if the tv isn't fast enough it cant be done in real time hence the delay.

John_Gray

I get a visible lip-sync delay when watching a live TV programme via my old Humax PVR and new Samsung TV (HDMI connection) compared with watching the live programme 'directly' via the TV.

Never had that problem with a truly ancient Sony Trinitron CRT TV (using Scart connection) now sadly scrapped because the speakers went!

boliston

RobTang wrote: »

The thing is for secondary devices eg Sky, xbox etc. You are not supposed to route the sound through the TV. ie it should always be; Device -> Soundplate -> TV


The HDMI spec says the TV is not allowed to just do a straight pass through of the audio to a different medium (eg optical) it has to re-encode the audio and if the tv isn't fast enough it cant be done in real time hence the delay.

if you plug the optical cable from the sky box direct to the sound bar then what happens if you want to use the tv for netflix?

neilmcl

wizzywig27 wrote: »

I have checked all systems and there is no sound delay in system preferences.

Are you sure about that. I'm sure there's an option on the Sky HD box to adjust for audio delays. I'd imagine something like the LG sound plate would have something similar.

wizzywig27

its there but not set up (so no delay)

boliston

neilmcl wrote: »

Are you sure about that. I'm sure there's an option on the Sky HD box to adjust for audio delays. I'd imagine something like the LG sound plate would have something similar.

My OH has got the newer "silver" 2tb box (the box is black but it's called a silver box for some strange reason)

I_have_spoken

The thing is for secondary devices eg Sky, xbox etc. You are not supposed to route the sound through the TV. ie it should always be; Device -> Soundplate -> TV

True, however these 'Soundplates' are very mean on HDMI inputs, some only have one!

OP, you may be better off with an HDMI switcher (https://www.amazon.co.uk/Switch-Kinps-Switcher-quadrupled-Bluray/dp/B01K1FXEKG) to route all inputs to the SOundplate

almillar

As RobTang says, you're supposed to connect Sky boxes, DVD players into the soundbar or amp, which THEN plugs into the TV. The soundbar or amp would then have delay controls if necessary, to overcome the lag of the TV processing and outputting the TV.
Doesn't help if you're trying to get sound out of the TV from Freeview or any smart features, but it's a start.
Ideally, you would have soundbar to TV via HDMI, and if both support ARC (Audio Return Channel) then the sound from the TV can 'go backwards' back down the HDMI lead to the soundbar.
Also as above, your Sky box does have delay settings in case they're necessary - my TV has big lag so I have to slow the sound down to the amp to keep the lips in sync.