Lip-Sync problems with AC3 over optical

Question

Level 1

127 points

Lip-Sync problems with AC3 over optical

I was reading an old archived thread about Lip-Sync problems on the Apple TV when using the optical output for audio and HDMI for video.

This problem seems to only affect AC3 soundtracks as when I switch off Dolby Digital from the Apple TV settings, the AAC track plays fine.

It seems that the synchronisation data that is collected via the HDMI interface between the TV and the Apple TV is not being applied to the AC3 stream that is output over the optical port.

Could someone confirm that if they've had this problem using the optical out for AC3 that it went away after connecting to an AV amp with HDMI support? I'm thinking of upgrading my AV amp and am hoping that getting one with HDMI inputs will solve this lip-sync issue.

Cheers

iMac 24" 2.8 GHz, Mac OS X (10.6.1), Time Capsule 1TB; AppleTV 160GB; iPod Touch 2nd Gen 32GB; iMac G5; iMac G3 DV

Posted on Oct 5, 2009 2:53 AM

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Answer 1

Oct 5, 2009 3:10 AM in response to Easybourne

My tv is set up to send audio to an amp and video to a tv, rather than through the amp. I have no issues with lipsync.

I have seen others mention this but have always put this down to the way the amp and tv manage the inputs rather than an tv issue.

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Answer 2

Easybourne Author

Level 1

127 points

Oct 5, 2009 3:18 AM in response to Winston Churchill

So you're using optical for Audio and HDMI for video like me? Or are you using component for video?

I should also point out that this seems to be a relatively new issue around last 6-8 weeks - prior to this all was fine.

The only things that have changed in this time are the latest Apple TV firmware and QuickTime updates. This is what makes me think its the Apple TV.

Also, as I stated this only affects AC3 audio.

Message was edited by: Easybourne

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Answer 3

Oct 5, 2009 3:24 AM in response to Easybourne

Easybourne wrote:
So you're using optical for Audio and HDMI for video like me?

Yes

Or are you using component for video?

No

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Answer 4

pvonk

Level 6

13,851 points

Oct 5, 2009 10:57 AM in response to Easybourne

Strangely enough, I find that British TV shows and movies that have magically been put on my ATV have a greater chance of audio-video sync problems - and jerky scenes when the camera panned. I have suspected the issue may be with how the original material was transferred to American formatted DVDs and then magically transferred to ATV. That's the only common thread I've found.

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Answer 5

Oct 12, 2009 8:08 AM in response to Easybourne

hmm unfortunately i have the same problem. But i only have it with dvd's i have ripped to my hard drive (that is, not with programs that i have purchased on itunes). And i only get the problem when i try to use 5.1 sound. If i just use the TVs sound then there is no lip sync problem. I can only guess that its cause i do not have hdmi on my amp, but i have been too lazy to upgrade it! That doesn't really help you does it?!!

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Answer 6

Easybourne Author

Level 1

127 points

Oct 12, 2009 8:16 AM in response to Daniel Colombi

{quote:title=Daniel Colombi wrote:}

That doesn't really help you does it?!!
{quote}

It helps to know I'm not alone! Thanks for posting.

I'm thinking that it may be something to do with the Apple TV's low processing power. I've got a couple of movies where lip-sync is pretty bad on the Apple TV, but when I play them in VLC Player on my mac (and select the AC3 track) they play perfectly.

What I was going to do was re-rip them at a slightly lower quality and see if the Apple TV can handle them a bit more easily... just a thought.

Also, all this seems to be a fairly recent phenomenon. I think it's something to do with the latest round of QuickTime updates, as all my encodes since before about six weeks ago seem fine. I'm only having trouble recently.

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Answer 7

Oct 12, 2009 12:51 PM in response to Easybourne

No problems here with ac3 lip sync. How are you getting the ac3 files and how are you adding them to the mov? Does the ac3 play back in sync in QT?

My TV signal is component, with the DD audio going optical to the amp. I always toggle back in forth in Quicktime to make sure it is in sync there. I've never seen an Apple TV sync issue with ac3: Either is plays correctly in QT and ATV, or neither.

As for the "British" DVDs, those are probably giving you problems because they are PAL material @ 25 fps, where film is 24 fps (and American, NTSC TV is 29.97). The Apple TV seems to be able to do a nice 24fps conversion to 29.97 (or 59.94, if you are using 720p), but probably doesn't work well with 25

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Answer 8

Easybourne Author

Level 1

127 points

Nov 2, 2009 5:28 AM in response to pvonk

pvonk wrote:
Strangely enough, I find that British TV shows and movies that have magically been put on my ATV have a greater chance of audio-video sync problems - and jerky scenes when the camera panned. I have suspected the issue may be with how the original material was transferred to American formatted DVDs and then magically transferred to ATV. That's the only common thread I've found.

Lately, I've been coming round to this idea too. The affected videos tend to be ones that from interlaced material (not all of them though).
There are a couple of older movies where this is happening too, and I think there may be problems with the way the DVD was telecined.

An interesting thing happened that led me to think that interlacing is not Apple TV's best friend:
I was using my Apple TV with a movie that works perfectly and is in sync when I have it connected via HDMI and use 1080p as the output resolution. I had cause to change to using the component outputs for a short while and I set the output of the Apple TV to 1080i, this resulted in the otherwise perfect movie suddenly playing out of sync. Changing to 720p over component fixed it.

Another problem movie is a concert video that was made by the BBC in PAL but was released on DVD in NTSC format. This exhibits terrible sync problems on the Apple TV - again, only with the AC3 track.

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