Recently, Ive noticed an initial audio delay after the video starts (up to 3 seconds) on the apple TV when starting a recording or a live channel. Im running the latest betas. Ive also tried going back to previous betas and even to the release version and it happens there as well.
Whatever is going on seems to have been aggravated by the release of TVOS 18.3, but honestly it might have crept up in 18.x for all I know. It seems worse in recent weeks. Its really bad now after upgrading to 18.3 a few days ago. It is particularly noticeable at times when you press pause for more than a few seconds. When you start playing again, the initial audio delay comes back. YUCKKK!
Ive spent some time narrowing this down.
Equipment :
Mac mini M4 running the latest beta release of the server
Apple TV 4k second generation.
Yamaha TSR 7850 surround AV receiver
Background:
There has been a long standing vulnerability with apple TVs and the way they interact with some ATMOS capabile AV receivers and soundbars.
If you google “apple tv initial audio delay” there are a bunch of threads out there.
Depending on the source material, it can take several seconds after starting a video for the audio decoders on some Av receivers and sound bars to decide what format to use if dolby ATMOS is turned on on the apple tv.
Ive known about this for a long time, but thus far this has never been an issue for me with channels until recently . I have played ATMOS, 5.1 surround and stereo material flawlessly for years in channels with no initial delays.
So something has changed.
After a lot of debugging (running TVOS 18.3) I’ve noticed the following:
On my apple TV 4K (2nd gen) Ive confirmed that this is ATMOS related. If you disable atmos in the apple tv settings the initial delay issue goes away. When investigating further, Ive noticed something interesting going on with the way channels is interacting with the Apple TV and my surround receiver.
I have a way through my AV receiver of monitoring the audio signal path.
As a baseline, with ATMOS enabled OR disabled, when playing a standard 5.1 surround sound music video in PLEX, i noticed the following:
As expected, the standard surround sound material comes in from the ATV as 5.1 linear PCM. This has always been the way CHANNELS behaved for me when I played the same file in channels.
Now, when I play the same source file with ATMOS turned off on the APPLE TV I get this when using channels:
Why is the apple Tv sending 7 channels of audio here when using channels? Its a 5.1 dolby digital file AC3 5.1. Same file played in plex is as above with 5.1 PCM. Note, in this case, there is no i initial audio delay in channels because ATMOS is turned off.
When I turn ATMOS back on, my receiver is getting this when I use channels.
@tmm1 @eric @maddox is this expected behavior with an AC3 5.1 file?
Im not sure how long ago this changed, but definitely Ive noticed different behavior in channels since the ATV 18.3 update.
Im happy to provide additional info, support etc.
Ive also tried channels on a second Apple TV same model. In this case it is hooked up to a linkpi HDMI decoder. It has no issues I suspect because it doesnt even support surround.