AC-4 Audio?

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HappyDude
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Re: AC-4 Audio?

Post by HappyDude »

I've noticed that if the hd home run app on an xbox and an apple tv doesn't detect the tuner on the network that atsc3 recordings won't play audio. Is that intentional? I'm guessing for license reasons.

NedS
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Re: AC-4 Audio?

Post by NedS »

HappyDude wrote: Wed Jul 07, 2021 6:55 pm I've noticed that if the hd home run app on an xbox and an apple tv doesn't detect the tuner on the network that atsc3 recordings won't play audio. Is that intentional? I'm guessing for license reasons.
The presence of the ATSC 3.0 unit should not affect recording playback. Can you tell me the device ID for your unit?

HappyDude
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Re: AC-4 Audio?

Post by HappyDude »

NedS wrote: Wed Jul 07, 2021 10:30 pm Can you tell me the device ID for your unit?
10818F82

hdhruser
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Re: AC-4 Audio?

Post by hdhruser »

I REALLY hope SiliconDust will release a version of the HDHR where 1) All four tuners can receive ATSC3, and 2) it can transcode AC4 audio to AC3 in real time (personally I'd also take EAC3 a.k.a. Dolby Digital+, which seems to have better channel separation, but not all receivers can handle it). I know there have been versions of the HDHR that did transcoding in the past but that was to compress the video, which takes a lot more processing power than transcoding the audio only. I'm certain SD is losing sales because nobody wants to drop $200 on a device that will only guarantee to give them video but not sound. I was reading a forum on another site (possibly Reddit but I don't recall for sure) where someone asked about using a HDHR to receive ATSC3 and others advised against it solely because of the audio issue.

The other thing I don't get is why the ffmpeg people are not all over this, because this is sort of their thing. They've included code in ffmpeg that would decode and encode in formats compatible with other Dolby formats (the aforementioned EAC3 is one example); I'd assume for legal reasons they need to reverse engineer the format but they have done that before. Even a not-quite-perfect conversion would be better than nothing, and I know there is some code floating around out there that can be patched into the ffmpeg source code to give it at least some ability to decode AC4 and (I would assume) transcode it to AC3, but if you're not a programmer then that patch is not real useful, even if you can find it. But the ffmpeg people seem to be treating that patch as if it were covered with Covid-19 virus for some reason?! I don't get it but then I am not a programmer.

SoNic67
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Re: AC-4 Audio?

Post by SoNic67 »

hdhruser wrote: Thu Jul 08, 2021 2:30 am I REALLY hope SiliconDust will release a version of the HDHR where 1) All four tuners can receive ATSC3, and 2) it can transcode AC4 audio to AC3 in real time (personally I'd also take EAC3 a.k.a. Dolby Digital+, which seems to have better channel separation, but not all receivers can handle it).
1 - how much are you willing to pay? I assume you meant "at same price"? With the current world-wide shortage of electronic chips, I am amazed that SD is manages to keep the same prices.
2 - that decoding and re-encoding would require a license from Dolby. I doubt that will be free or even granted. They pushed the AC-4 for a reason... and with lots of money. They won't just give up to that.
hdhruser wrote: Thu Jul 08, 2021 2:30 am The other thing I don't get is why the ffmpeg people are not all over this, because this is sort of their thing. They've included code in ffmpeg that would decode and encode in formats compatible with other Dolby formats (the aforementioned EAC3 is one example); I'd assume for legal reasons they need to reverse engineer the format but they have done that before
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HappyDude
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Re: AC-4 Audio?

Post by HappyDude »

HappyDude wrote: Wed Jul 07, 2021 6:55 pm I've noticed that if the hd home run app on an xbox and an apple tv doesn't detect the tuner on the network that atsc3 recordings won't play audio. Is that intentional? I'm guessing for license reasons.
Correction, I'm only seeing this on the apple tv

NedS
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Re: AC-4 Audio?

Post by NedS »

HappyDude wrote: Thu Jul 08, 2021 11:45 pm
HappyDude wrote: Wed Jul 07, 2021 6:55 pm I've noticed that if the hd home run app on an xbox and an apple tv doesn't detect the tuner on the network that atsc3 recordings won't play audio. Is that intentional? I'm guessing for license reasons.
Correction, I'm only seeing this on the apple tv
Weird. I'll let the dev team know and see if we can figure out this mystery.

Watcher
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Re: AC-4 Audio?

Post by Watcher »

hdhruser wrote: Thu Jul 08, 2021 2:30 am .... 2) it can transcode AC4 audio to AC3 in real time
SD has stated their intention to provide a (cloud based) AC-4 to <something> transcoding solution (likely for their applications). Details, and availability dates have not been shared.
The other thing I don't get is why the ffmpeg people are not all over this, because this is sort of their thing.
There are many possibly parts to this answer. First, having a FFmpeg transcoder solves little for most commercial products. Dolby has made available a free/low-cost SDK solution for those licensing their technology (and commercial products *must* license the technology), so those commercial products already can deal with AC-4 without investing their efforts into a 3rd party solution. Secondly, FFmpeg work is performed by those with interest, and competency in audio codecs, and are willing to work on such. For a number of very good reasons those outside of the US have not expressed great interest in AC-4, and those in the US are not likely to touch it with a 3 meter pole because they would choose not to be a target. And that goes to a third point, that Dolby, unlike some other IP holders, *will* go after products (and users), even if "free", that utilize their IP. So (let us imagine) there is a product call Kodi that uses FFmpeg to decode AC-4 into something else. It would be forced to be removed from most common distribution channels due to license violation if they do not send their fees to Dolby. As an aside, the patches that have been floating around are not considered complete or robust, so the FFmpeg developers are not interested in them at this time (so those developers have to step up and go through the entire contribution process, or get out of the way).

Many apps are hoping that the platforms themselves will offer a AC-4 codec (nvidia has with their latest shield release) so they can just use the platform codecs. Whether the common platforms will do so is still a work in progress.

ebo
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Re: AC-4 Audio?

Post by ebo »

Watcher wrote: Sat Jul 10, 2021 9:02 pm So (let us imagine) there is a product call Kodi that uses FFmpeg to decode AC-4 into something else. It would be forced to be removed from most common distribution channels due to license violation if they do not send their fees to Dolby.
. . .
Many apps are hoping that the platforms themselves will offer a AC-4 codec (nvidia has with their latest shield release) so they can just use the platform codecs. Whether the common platforms will do so is still a work in progress.
I use Kodi on a Raspberry Pi to watch most of my videos including live or recorded from an HDHR. The Pi 4, which I don't have, can decode HEVC in hardware but not AC-4. I hope they'll come out with a model that can, most likely requiring the end user to buy a licence for a few dollars as they did for MPEG-2. I'd be willing to pay that but I'm not going to buy a new top-level AVR just for that capability.

A good alternative would be an HDHR model that can transcode AC-4 to AC-3 or something else that my Denon 3808ci can deal with (and no, I didn't pay top-dollar for that either; I bought it for $100 at an estate sale). I won't be buying any ATSC 3.0 tuner until I can play its output without any hassle. But when and if I do buy one it will almost certainly be an HDHR.

hdhruser
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Re: AC-4 Audio?

Post by hdhruser »

SoNic67 wrote: Thu Jul 08, 2021 4:57 am
hdhruser wrote: Thu Jul 08, 2021 2:30 am I REALLY hope SiliconDust will release a version of the HDHR where 1) All four tuners can receive ATSC3, and 2) it can transcode AC4 audio to AC3 in real time (personally I'd also take EAC3 a.k.a. Dolby Digital+, which seems to have better channel separation, but not all receivers can handle it).
1 - how much are you willing to pay? I assume you meant "at same price"? With the current world-wide shortage of electronic chips, I am amazed that SD is manages to keep the same prices.
2 - that decoding and re-encoding would require a license from Dolby. I doubt that will be free or even granted. They pushed the AC-4 for a reason... and with lots of money. They won't just give up to that.
Well thank you Debbie Downer. But SD has a problem then, because if people buy HDHomeRuns to use with their existing equipment and expect them to just receive ATSC 3 and convert it to something that can be viewed on their existing TV, and then they get no audio, many people at that point will just return those units for a refund. They won't know, and probably won't care about the technical reasons they aren't getting sound; they'll just be saying "the damn thing doesn't work" and possibly telling their friends the same thing.
SoNic67 wrote: Thu Jul 08, 2021 4:57 am
hdhruser wrote: Thu Jul 08, 2021 2:30 am The other thing I don't get is why the ffmpeg people are not all over this, because this is sort of their thing. They've included code in ffmpeg that would decode and encode in formats compatible with other Dolby formats (the aforementioned EAC3 is one example); I'd assume for legal reasons they need to reverse engineer the format but they have done that before
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SoNic67
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Re: AC-4 Audio?

Post by SoNic67 »

hdhruser wrote: Mon Jul 12, 2021 4:47 pm Well thank you Debbie Downer. But SD has a problem then, because if people buy HDHomeRuns to use with their existing equipment and expect them to just receive ATSC 3 and convert it to something that can be viewed on their existing TV, and then they get no audio, many people at that point will just return those units for a refund.
So that's life. You want to view ATSC 3.0, you need a new TV or a new sound bar/system. Both my TV and my soundbar can decode AC-4.
More, SD application has sound also on my Windows 10. So... there is a way.
They don't have to fix whatever software you are using.

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nickk
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Re: AC-4 Audio?

Post by nickk »

As noted above, we are working on a cloud assisted transcode approach that will enable client devices that lack AC-4 support to play ATSC 3.0 channels.

djp952
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Re: AC-4 Audio?

Post by djp952 »

nickk wrote: Mon Jul 12, 2021 5:35 pm As noted above, we are working on a cloud assisted transcode approach that will enable client devices that lack AC-4 support to play ATSC 3.0 channels.
This sounds extremely interesting. Do you anticipate this transcoding approach may be available to third-party applications that operate within the HDHomeRun ecosystem or will this be limited to SiliconDust intellectual properties?

I'm not envisioning how this could possibly work in realtime via a cloud service but am looking forward to see how you pull this off (because you will). Are you planning to delay playback of the video stream so that it will sync with the transcoded audio stream from the cloud service or are you thinking that the audio can be transcoded quickly enough to not delay playback? Color me interested in the details!

rpcameron
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Re: AC-4 Audio?

Post by rpcameron »

nickk wrote: Mon Jul 12, 2021 5:35 pm As noted above, we are working on a cloud assisted transcode approach that will enable client devices that lack AC-4 support to play ATSC 3.0 channels.
Instead of worrying about and solving edge cases for technologies that still have yet to hit major metropolitan areas—Los Angeles still has no ATSC3 feeds—why not focus development effort on promised goals still yet to be met; I'm sure cable users would still like to have the recording ability promised 6+ years ago.

Please deliver upon current company promises before addressing un-asked-for features: DRM recording, grid-style guide, and operation without an active internet connection. If you can't deliver upon previously promised goals—that other software can do—why should users place any trust in your undelivered claims?!

(It's true you never promised a grid-style guide, but a multitude of users have requested it. It is as important as DRM recording, in my opinion.)

nickk
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Re: AC-4 Audio?

Post by nickk »

djp952 wrote: Mon Jul 12, 2021 7:46 pm This sounds extremely interesting. Do you anticipate this transcoding approach may be available to third-party applications that operate within the HDHomeRun ecosystem or will this be limited to SiliconDust intellectual properties?
It could potentially be opened for other apps to use if we can cover the cost of the service.
djp952 wrote: Mon Jul 12, 2021 7:46 pm I'm not envisioning how this could possibly work in realtime via a cloud service but am looking forward to see how you pull this off (because you will). Are you planning to delay playback of the video stream so that it will sync with the transcoded audio stream from the cloud service or are you thinking that the audio can be transcoded quickly enough to not delay playback? Color me interested in the details!
The protocol and service has been optimized for near real time playback.

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