AC3 Passthrough

Help and support for HDHomeRun DVR and HDHomeRun software for Windows 10, Mac, Android, XBox, etc.
thedoomster
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Re: AC3 Passthrough

Post by thedoomster »

Here's another little nugget of information. I found that if I turn on AC3 Passthru in HDHR, then exit and open Live Channels, I get 5.1 Dolby as expected and dialog is in sync. If I exit and open HDHR to the same channel, dialog is out of sync, with delay getting even worse over time or if I change channels. If I then exit HDHR and re-open Live Channels, it's out of sync there now too! If I exit and Force Stop Live Channels, then re-open Live Channels, dialog is back in sync. And stays in sync - until I change channels, then it's out of sync again.

This is on SONY Android TV v8.0.0 with HDHR Prime and about 400 channels, most of which are DRM-protected.

nickk
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Re: AC3 Passthrough

Post by nickk »

thedoomster wrote: Thu Jan 21, 2021 10:50 pm Here's another little nugget of information. I found that if I turn on AC3 Passthru in HDHR, then exit and open Live Channels, I get 5.1 Dolby as expected and dialog is in sync. If I exit and open HDHR to the same channel, dialog is out of sync, with delay getting even worse over time or if I change channels. If I then exit HDHR and re-open Live Channels, it's out of sync there now too! If I exit and Force Stop Live Channels, then re-open Live Channels, dialog is back in sync. And stays in sync - until I change channels, then it's out of sync again.

This is on SONY Android TV v8.0.0 with HDHR Prime and about 400 channels, most of which are DRM-protected.
Checking, are you using the speakers built into the Sony TV?

thedoomster
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Re: AC3 Passthrough

Post by thedoomster »

To Nick: No, I'm using an ARC connection to a SONY A/V receiver, speakers set to External.

Jedi71
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Re: AC3 Passthrough

Post by Jedi71 »

New Information on my side.

I took the Sonos Arc and LG B7 TV using ARC audio output out of the mix.

Now I am pushing a Yamaha A/V receiver with the Shield Pro, and outputting video to the TV from the receiver. And all is well with the world.

Using the Shield and the Sonos Arc for all other applications was flawless. It wasn't until using the HDHomerun app that I ever had an audio sync issue.

So I dragged out the old equipment and voila, all apps, including HDhomerun, using Dolby Digital, is fine. I don't know why the LG B7 couldn't process the Dolby Digital like it was supposed to, but obviously it couldn't. The Yamaha can.

Now if we can work on why Dallas 5.1 NBC KXAS has blocky static on Nvidia products and I will have no issues at all.

jasonl
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Re: AC3 Passthrough

Post by jasonl »

Jedi71 wrote: Fri Jan 22, 2021 5:21 pm Now if we can work on why Dallas 5.1 NBC KXAS has blocky static on Nvidia products and I will have no issues at all.
NVIDIA's video decoder is broken. The end.

Jedi71
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Re: AC3 Passthrough

Post by Jedi71 »

I understand that, but I'm sure a sizable amount of HdHomerun users will be running it on a Shield. HDHR and Nvidia need to work together because the Shield is ruining HDHR's product. And what other stations are doing, or will do, what KXAS is?

tmm1
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Re: AC3 Passthrough

Post by tmm1 »

NVIDIA has already confirmed this bug is burned into their video decoder chip and is not something they can fix.

Jedi71
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Re: AC3 Passthrough

Post by Jedi71 »

Do you know what is behind this? KXAS 5.1 is the only channel that triggers this chip defect. And it must only be in the OTA signal because 5.1 plays just fine on YouTube TV and Sling TV over the same Nvidia Shield.

And 103 other OTA channels in the Dallas area are able to broadcast in such a way that doesn't trigger this chip defect. What is it that KXAS 5.1 is doing that every other station in Dallas isn't

Once I have information on what this is, I'm going to petition KXAS to cut it out. 😁

And whatever it is, is it something that could be removed when they eventually broadcast in ATSC 3.0?

It seems that many people know this is an ongoing issue. Should HDHR have a warning on the site that says: Dallas area users are currently suggested to not use our products with an Nvidia Shield?

kyl416
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Re: AC3 Passthrough

Post by kyl416 »

Jedi71 wrote: Sat Jan 23, 2021 12:11 pmAnd it must only be in the OTA signal because 5.1 plays just fine on YouTube TV and Sling TV over the same Nvidia Shield.
Streaming apps like YouTube and Sling don't give you interlaced MPEG2, they deliver thier stations as progressive scan H264 with adaptive bitrate streaming. And for some locals they don't use the OTA signal at all as a source, the use a made for streaming feed with dynamic ad insertion and some blackouts for content the station and/or network doesn't have the streaming rights to.
And whatever it is, is it something that could be removed when they eventually broadcast in ATSC 3.0?
ATSC 3.0 doesn't use MPEG2 for video, they use HEVC, which has its own set of problems because some decoders don't support interlaced HEVC, which is part of the ATSC 3.0 spec.
It seems that many people know this is an ongoing issue. Should HDHR have a warning on the site that says: Dallas area users are currently suggested to not use our products with an Nvidia Shield?
Nvidia already knows about the bug and acknowledged it several years ago on their official forums after numerous people brought it up, they just refuse to do anything about it and continue to design and ship graphics cards and Shield devices with that defective MPEG2 decoding chip. And this issue is not isolated to Dallas or KXAS, it affects stations across the country, it's just that for your area KXAS is the only station affected. Nvidia likely doesn't consider it a high priority issue since only a fraction of their userbase in the USA uses the shield for OTA TV, while most of the world uses H264 or HEVC instead of MPEG2 for free to air HD broadcasting and streaming services like Sling, YouTube, Netflix, Hulu, Prime, Disney+ etc don't use MPEG2 at all.

Jedi71
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Re: AC3 Passthrough

Post by Jedi71 »

Hey, thanks for the information! Truly, I've googled Nvidia, 5.1, KXAS, etc for weeks and never found anything that explained what the problem is.

In fact, with "5.1" also being involved in sound, the search results were very muddied by information I was not looking for. 😁

So this means that in Dallas, KXAS is the only signal that's encoded in MPEG2?

nickk
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Re: AC3 Passthrough

Post by nickk »

We are working on a solution to fall back to software decode on this channel (with the ability to blacklist other channels in other areas on Shield in the future).

We don't have a good solution for recordings yet.

Nick

Jedi71
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Re: AC3 Passthrough

Post by Jedi71 »

Thanks for the update Nick. All I ask is that it's a known issue. And it is. 👍

jasonl
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Re: AC3 Passthrough

Post by jasonl »

WFAA used to have the same problem. They switched from 1080i to 720p and it went away. I wouldn't suggest that for KXAS though, because it would make their broadcast worse. WFAA got better by going to 720p because the ABC network is 720p, so now there's one less conversion involved, vs. NBC which is 1080i.

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