AppleTV sound issue, "mono phase cancellation" when playing back from DVR

Channels Apple TV
#1

I am (and have been for a while) experiencing and issue with Channels app on AppleTV, where the sound of a DVR playback video will have a sound issue, which sounds to me like center panned phase cancellation. This is a once and a while issue, and is not able to be consistently repeated, however I notice it after playback has been paused another app is used for a while. When I come back to the Channels app, I can hear audio but only certain parts of it. For example, when I'm playing back a football game broadcast and the issue happens, I can only hear crowd noise and some music beds. Any voice over sound is completely absent. This issue persists through out playback and also affects all commercials in the broadcast.

I'm an audio engineer and the best way I can explain the issue, is that is seems like several channels of audio are summed, and audio information that is equal amplitude and equal phase gets cancelled out, whereas the audio that is out of phase and same amplitude remains. I'm not sure how many streams of audio are getting recorded, but if it's just L&R, then it makes sense that things like the audio from announcers in a sports broadcast would be fully cancelled, yet sources of stereo information (like crowd noise) would still be present.

I am able to rectify the issue with a force quit of the Channels app, and then resume playback.

Anyone else have this issue before?

Also, I'm running Channels DVR Server version 2021.08.12.0054 if that matters.

#2

I have seen a similar behavior once in a great while. I’m not sure if it’s phase cancelation in my case. What I am noticing is that the center channel (typically the dialog in 5.1 program material) is completely silent.

I’m running an Apple TV 4K into a Yamaha 5.1 surround system.

I also have to close the app with the control panel and reopen, but this happens so infrequently that I have not been able to reproduce it reliably enough to share with the developers and to troubleshoot further.

1 Like
#3

I too have had the center channel where dialogue typically is disappear. It’s incredibly rare, like once every 6 months.

#4

@andydibben

Ironically, this morning I was using airpods with my Apple TV 4K. The show was recorded in 5.1 from the local broadcast network.

The airpods are obviously stereo, and this scenario completely removes my home theater from the equation, because this audio in stereo directly from the Apple TV.

This time I did observe some kind of massive center channel attenuation of the dialog. I did hear very low dialog in the left and right sound field panned really wide in each ear. Clearly not normal.

These were not a AirPods Pro’s, so we can rule spatial audio out of this equation.

In this case, I wanted to see if the audio issue was stuck to all programming, so I played a known two channel recording and it played fine. Then when I opened the first program, the audio center material was panned correctly and volume was as expected.

In case you haven’t already done this - maybe next time you see it, maybe try playing a different recording , then go back to original - instead of using the app switcher to shut down channels. This would help narrow down whether what you are seeing is the same thing I saw today.

We should keep this thread open and continue to report our findings to help narrow this down.

Btw - also an audio engineer

Best

1 Like
#5

Are these atsc1 or atsc3 feeds?

#6

This is the same thing I emailed support about the other day. For me it is atsc1.

I am able to fix it by just switching audio tracks or exiting the recording and going back in.

#7

Here are the audio track(s) details from a particular recording that I experienced the issue with:

Track #1: ATSC A/52A (AC-3)
5.1(side) eng 384kbps

Track #2: ATSC A/52A (AC-3)
stereo spa 192kbps

#8

I can reproduce this with cable channels, too. Not an ATSC quirk.

If i pause a recording, leave the ATV as-is until the TV/ATV idle timer puts the ATV into standby, "power back up", then re-enter the Channels client, where it's still waiting on my paused place - playing from there kills the center channel.

#9

Hmmm....I'm going to try that today and see if I can replicate.

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#10

ATSC 1. Plain vanilla

#11

I’m having a similar problem, have been for a few weeks now. I don’t know the nature of the problem because I haven’t dug into it yet, but the sound is often silent when I launch the app. I have to close and reopen many times before the sound comes back. I’ve NEVER had a problem with Channels until now, but this sucks.

I’m using eARC into a Sonos Arc from a Samsung TV for my sound, but I’ve been using this setup for quite some time and this is a relatively new problem.

I don’t know troubleshooting needs to be done, but I’m willing to help provide info if needed.

#12

I was able to replicate this twice this evening. I was able to restore the audio by Swiping down to reveal the options menu, deselecting the English audio language (which in my case mutes all audio since there is no other language option), then selected English again.

#13

I was watching this morning using my AirPods connected directly to my ATV and experienced this today. So that rules out any kind of HDMI handshake issue to the TV/soundbar. Either the issue is with ATV or Channels app. But since it never happens with any other ATV app, seems like a Channels issue. Running TestFlight version, always on the latest build. And I've only experienced it since watching OTA with 5.1 sound.

#14

I experienced exactly this same thing yesterday, playing last week’s episode of Saturday Night Live. I thought something was wrong with my recording. I restarted and still had the issue. I watched something else, waited a few hours. Later on I went back to try the same recording again, and this time the audio was fine. It was super weird.

#15

I’ve seen this with AirPods as recently as today. I’ve always been able to get rid of it by using the app switcher and closing down the app. Completely loose “center” channel.

I’m on TVOS 15.1

#16

I experience this often when the video goes into pip. It’s like the center channel disappears. Force quit fixes it.

#17

Issue still occurring here and there, more consistent now on OTA broadcast recordings.

I have found that the fastest and most reliable way to stop the issue is to use the options menu and select another audio stream…then go back to your original audio stream. For me, that fixes it every time. Credit for that work around goes to A previous commentor on this thread.

#18

With the latest TestFlight build we have a possible fix for this problem, so it would be helpful if you try that and confirm if its fixed or not.

See BETA: Audio improvements for Apple TV and iPhone/iPad

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#19

Happy to test this but I am not able to join the Beta program and accept the terms. I’m getting this message when I attempt to accept:
“You can't vote because you can't post in this topic.“

Please advise…

#20

The link is on getchannels.com/beta