Bitstreaming audio / signal question

Channels Android TV
#1

I am curious about how audio is bitstreamed to the receiver when using the Nvidia Shield. I notice that when I pause live TV, my receiver stops getting a signal from the Shield. On older receivers like mine (an Onkyo 805, HDMI 1.3 era) , this creates a dropout while the signal is checked and re-established. It also has the potential to desynchronize the audio and video entirely. The only thing that resyncs everything is rewinding/fast forwarding a couple of times to get everything lined up again. I can provide a video clip if you like.

On Windows Media Center, it seemed like there was some type of audio keepalive happening under the hood - if I paused a program that was Dolby Digital, you could immediately resume it without there being any dropouts. It would only ever change if the actual input stream changed (ie a commercial that was in regular 2 channel).

Is this behavior intentional, a limitation of Android, a limitation of the Shield, just my old receiver not being able to handle the way this modern device is sending, etc? Just curious.

#2

I assume you have Surround Sound enabled in the app Player Settings?

#3

Yes, that’s correct. Obviously when surround sound is off, I only get 2 channel sound. FF/RW/Pause do not cause the same behavior when surround sound is set to off - the receiver simply displays ‘Stereo’ the entire time as per normal.

#4

To be honest I’m not sure. The Android Audio APIs are a bit of a mess, so I wouldn’t be surprised if that’s to blame.

I’m curious if you see the same behavior in the official HDHR android app?

#5

I did some work on this tonight. Yes, it does happen with the HDHomeRun android app. Happens with Plex and Kodi as well. It seems a little bit more pronounced on Channels app vs. the others, but it’s not a major difference - we’re talking milliseconds here. I took some video and can upload to YouTube if you like, but at this point I think you’re probably right that it’s a combo of the Android Audio API and my ancient receiver.

It’s interesting that my Xbox 360 extender which used to be the endpoint for Windows Media Center doesn’t exhibit the dropout problem upon FF/RW/Pause where the signal is lost from the receiver - but rather shows the audio normalization setting on the display instead of dolby digital. Very odd, it does look like an audio keepalive of some kind being sent by the Xbox 360.

#6

Thanks for checking. It might be possible for us to play silence while paused to keep the receiver alive, but I’m not sure. Will have to play with it when I have some time.

#7

Hey, don’t junk up your nice modern code base on account of my legacy crap! :smiley: If I had an Apple TV 4k to test on, I would be curious to see if the behavior is the same. At least your app continues to properly send the Dolby signal when bitstreamed to the receiver – more than I can say for the HDHomeRun app (it randomly toggles back to stereo when you pause sometimes). Thanks for whenever you do get a chance to investigate.

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#8

What exactly does the "Surround Sound" setting do in the Channels app?

Is this the app processing the source audio to make it a Simulated Surround that many TV's or sound bars have their own settings for? Or down-mixing a 5.1 source to 2.0?

Or is adjusting this setting allow for multi- audio stream pass-through of some sort.

I ask because the 2019 Shield Pro i have that is the player, has its own Dolby Surround processing mode, and the Vizio 2.0 sound bar connected to the TV, has its own "Surround" mode that processes any audio it gets. Don't want to double or triple mix the audio stream.

Source is HDHR Prime as well as the TVE as second tuner.

#9

Surround Sound off downmixes to stereo and sends out only 2 channels of audio.

Surround Sound on sends all available channels to the OS. The SHIELD will receive 6 channels of audio and do its own processing before sending it out over HDMI.

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#10

This is why a Passthrough is needed so the app does zero processing. I see the same drop on my Sony Android TV that other apps don't do. I can test the HdHomerun app again but I don't remember it happening with it.