Quote:
Originally Posted by Ghostman84 /forum/post/16781840
I keep reading how HDMI 1.3b and 1.3c support "auto lip sync correction". I purchased two HDMI 1.3c cables hoping to correct the lip sync issue between my amp and Blu Ray player. It didn't seem to help, but then I set both the receiver and the player at a 30ms delay and everything seemed pretty much in sync. Is this how it works?
This is an OPTIONAL feature of HDMI V1.3. Not all HDMI V1.3 devices will support it. It is something that has been way over-hyped.
The way it works is that an earlier device, which handles audio, can inquire of a later device, which DOESN'T handle audio, how much video delay the later device believes it is adding. The earlier device can then also delay the audio that much. Typically the later device is a TV and the earlier device is an Audio Video Receiver (AVR). The expectation is that the AVR is processing the audio, but NOT the video and so can't know how much video delay is being introduced except by asking.
The amount of video delay added by pretty much any TVs is a constant regardless of your settings in the TV or what you are watching. In fact the info returned by the TV when the AVR inquires is almost certainly a fixed number that's just built into its HDMI data block -- without regard to any settings you might have made in the TV. Which means you'd get just as good a result by MANUALLY setting the proper delay in your AVR -- using the simple test found on many calibration DVDs.
The real problem with this "automatic" adjustment is that it does NOT help if some even EARLIER device is screwing up, or if there is an error in the content to begin with. And in reality, these are the bulk of the problems people actually see as lip sync errors.
For example, some cable/satellite providers have been known to send out signals where the video is actually AHEAD of the audio -- i.e., as if they already applied too much audio delay before the signal was sent out. Adding additional audio delay just makes things worse. And there is no mechanism to add VIDEO delay so you are stuck.
In your case the problem appears to be a BUG in your disc player that is generating 60ms of uncorrected video delay. This should not be happening. The player SHOULD be sending out audio and video in sync for all the different types of discs it plays and for all settings.
Again, this is almost certainly a bug in the player. It is almost certainly NOT due to video delay being added by your receiver or TV. So even HDMI V1.3 doesn't anticipate that "automatic" lip-sync correction would handle it. In addition, I don't believe there are ANY HDMI V1.3 players out there which actually implement "automatic" correction -- which would require them to get video delay values from both the receiver and the TV and then add audio delay to their disc playback. This "automatic" stuff, if you find it at all, is almost certainly only going to do anything in AVRs.
And your AVR can't "automatically" correct the problem in the player because there is no way to inquire of an earlier device how much it is screwing things up. And since it's a bug in the player, even if there WAS a way to get that data, the player would probably just provide an incorrect answer!
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Anyway, you appear to have a 60ms bug in your player. It happens. You are fixing that by adding 30ms delay in the player and an additional 30ms delay in your AVR. That's fine as a workaround SO LONG AS that delay value you have put into your AVR doesn't screw up any OTHER sources you are playing through that AVR, such as your cable/satellite TV.
Also keep in mind that some discs already have screwed up lip sync in the contents coming off the disc. There is no way to automatically correct for that. You have to make MANUAL adjustments disc by disc or just live with the problem on the faulty discs. To test what's really going on in your player you need to use a disc that doesn't have any such problem -- typically a calibration DVD.
The worst case is when the lip sync varies as you play the disc. This too is often due to a bug in the player. Error builds up and gets worse as you continue playing the disc. Often, pausing the disc or a brief reverse will cure the problem -- for a while.
If you conclude your player really is causing this delay, then check for a firmware update for your player.
--Bob
