Sync Errors

Hello

I have recently been having some sync errors (as with many others reading here).  At first I thought that they were mainly with MKV files containing 5.1 audio (A_AC3) as it becomes when converted to MKV.  (I don’t know the difference between AC3 and A_AC3 - I am sure someone else can fill me in on that one)

However, as I did further tests playing VOB files taken directly from a DVD (no conversion at all) I found out that it was mainly due to the digital output on the WDTV Live box.  Changing the output to stereo resulted in perfect sync, as soon as it was changed to digital it becomes out of sync.

I went through many, many emails with WD technical support, only to be told in the end that I have to change the audio bit rate from 48.0KHz as the WDTV Live does not support 48.0KHz audio.  I am totally gob-smacked by this as all DVD’s audio is at 48.0KHz.  Are WD really expecting everyone to remux and downgrade their video files every time they want to play anything?

This was the reply I got:

Our second level support sent me the following answer for the issue you are having:

Sampling rate : 48.0 KHz !!!
This is 48000 Hz, that’s why it’s out of sync

Two different formats, same media. The sync signal is surely wrong. It’s not a matter of the WDTV live as it wouldn’t affect two different files. You should be aware of the fact that in case of playing the files on a computer you will surely not notice any issues as you will be using a full fledged GPU and a multi-core CPU to take care of it and will thus support any sampling rate. Stereo output is ANALOG and does not depend on the sampling rate which only affects digital output.

Remux and downsample is the solution :wink:

Can this really be true?

Thanks.

Interesting. I’m going to have to go back to one of the older files I have to see if that’s the issue with the de-sync problem. I never really tried it with the stereo cable, as my setup is digital. Thanks for the idea anyway.

eon_designs wrote:

Hello

 

I have recently been having some sync errors (as with many others reading here).  At first I thought that they were mainly with MKV files containing 5.1 audio (A_AC3) as it becomes when converted to MKV.  (I don’t know the difference between AC3 and A_AC3 - I am sure someone else can fill me in on that one)

 

However, as I did further tests playing VOB files taken directly from a DVD (no conversion at all) I found out that it was mainly due to the digital output on the WDTV Live box.  Changing the output to stereo resulted in perfect sync, as soon as it was changed to digital it becomes out of sync.

 

Welcome to the forums.

There shouldn’t be any sync issues with properly converted files.  Two things immediately occur to me.

  1. How are you creating your MKVs?  Using Handbrake with the High Profile preset (but output type changed to MKV) shouldn’t be a problem at all (you can either passthrough AC3/DTS or convert to AAC as desired).

  2. Using “digital” requires there be decoding on the other end of the stream.  Normally this is a function of an AVR.  When this happens the video is decoded by the display and the audio is decoded by another device and this is well known for causing sync issues – this is why nearly all modern AVRs them nowadays have a “lip sync” or audio delay function.

This isn’t a Live issue – it’s just the way things are.  You can solve the problem by properly adjusting your AVR for the right delay.  I have three Live units (and three different AVRs) and the sync issue is different for each one (playing the exact same files).  I adjust each AVR for the proper sync and then don’t worry about it anymore (one of my AVRs and display combos doesn’t need ANY adjustment – the other two need adjustment but differ from each other in how much).

mkelley, good detailed reply.

I had another answer from the WD support team which I now find totally unbelievable.  They have told me that all files need to be converted from 48.0KHz down to a lower sample rate!

I asked if this was true for all DVD vobs and BluRay M2Ts files taken straight from the various discs and they said that “unfortunately you will have to lower the sampling rate for all the 48.000 files, for the WD TV Live”

I really can’t believe this to be true.  So in fact they are saying that it will not play DVD’s, ISO’s or any other native files without converting them.

If I had known this I would certainly not have bought this product?

Please tell me they don’t know what they are saying?  Please?

Uh, no.  He doesn’t know what he’s talking about, unfortunately.

I think every single MKV I have has 48KHz sample rate on audio, and I have no issues at all.