AC-4 Audio?

ATSC 3.0 Forum
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CBme
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Re: AC-4 Audio?

Post by CBme »

The 12-29 app update for Nvidia Shield has fixed the crashing when switching from the SAP audio our stations default to, to the 5.1 english audio. For my (non atmos) receiver that shoves the dialog into the left surround channel (on my pc in stereo it shoves in the left site) but the audio-switch crashing and stuttering video seems to have been resolved for this device. Points for progress!
Last edited by CBme on Mon Jan 04, 2021 10:10 pm, edited 1 time in total.

talkenrain
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Re: AC-4 Audio?

Post by talkenrain »

CBme wrote: Wed Dec 30, 2020 3:05 pm The 12-29 app update for Nvidia Sheild has fixed the crashing when switching from the SAP audio our stations default to, to the 5.1 english audio. For my (non atmos) receiver that shoves the dialog into the left surround channel (on my pc in stereo it shoves in the left site) but the audio-switch crashing and stuttering video seems to have been resolved for this device. Points for progress!
Yes, HDHOMERUN 20201229 for Nvidia Shield Pro, addressed the crashing problem (Thank you very much). Audio is still firmly planted in ether the left front channel or the left surround channel (depending on the local channel) using a 7.2.4 atmos system.

mooninite
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Re: AC-4 Audio?

Post by mooninite »

peanutbutter71 wrote: Mon Dec 28, 2020 3:09 pm I compiled this fork of ffmpeg on linux:

https://github.com/richardpl/FFmpeg/tree/ac4

I don't think this is in the main trunk for ffmpeg, but this is at least promising.
That branch is against the main trunk. I compiled a 4.3.x version and Kodi now plays audio for ATSC 3.0 Dallas, TX stations (H.265 + AC-4).

I expect it will take a few months for slower distributions to get ffmpeg 4.4 / 5.0 that will carry this support, but we'll be there much sooner than I guessed.

Alderem
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Re: AC-4 Audio?

Post by Alderem »

Just saw that mentioned on the Plex forums. Fantastic news.

thully
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Re: AC-4 Audio?

Post by thully »

It seems like the Chromecast with Google TV works with AC-4 audio with the latest firmware and HDHomeRun app. I’m using it plugged directly into the TV (no receiver). Audio is a little bit out of sync, though...

ferrellsl
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Re: AC-4 Audio?

Post by ferrellsl »

I completed a successful MSYS2 x64 build of ffmpeg that supports AC-4 audio streams and everything is working great for ATSC3.0/AC4 streams in the greater Phoenix area. For those who want to run the binaries outside of the MSYS2 shell, you will need to copy the following DLL files to the folder where your ffmpeg binaries ultimately reside.

They are:
libbz2-1.dll
libiconv-2.dll
libintl-8.dll
liblzma-5.dll
libstdc++-6.dll
libwinpthread-1.dll
libzstd.dll
SDL2.dll
zlib1.dll

On my system these DLL's are located in: C:\msys64\mingw64\bin

For those who want to conduct their own build, you can get the source for the AC-4/WIP here: https://github.com/richardpl/FFmpeg/tree/ac4

For those who don't want to build from source, you can download the Windows binaries from my DropBox account here: https://www.dropbox.com/s/eene7ecard5xk ... 4.zip?dl=1

An example command to play channel 161.1 here in Phoenix follows: C:\ffmpeg\bin>ffplay -i "http://192.168.2.142:5004/auto/v161.1?transcode=native" -ac 4
Substitute the IP address above with the correct IP address for your HD Homerun Tuner.


Enjoy!
Last edited by ferrellsl on Mon Jan 18, 2021 8:18 pm, edited 2 times in total.

jasonl
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Re: AC-4 Audio?

Post by jasonl »

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Lost Dog
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Re: AC-4 Audio?

Post by Lost Dog »

mooninite wrote: Wed Dec 30, 2020 9:43 pm
That branch is against the main trunk. I compiled a 4.3.x version and Kodi now plays audio for ATSC 3.0 Dallas, TX stations (H.265 + AC-4).

I expect it will take a few months for slower distributions to get ffmpeg 4.4 / 5.0 that will carry this support, but we'll be there much sooner than I guessed.
I compiled the AC-4 branch of ffmpeg and using ffplay I got audio from a ATSC 3.0 stream!!! Woo hoo! This is a start!

How did you get Kodi playing the AC-4? Did you have to compile Kodi against the ffmpeg branch?

kohaiut
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Re: AC-4 Audio?

Post by kohaiut »

ferrellsl wrote: Thu Jan 14, 2021 5:44 pm I completed a successful MSYS2 x64 build of ffmpeg that supports AC-4 audio streams and everything is working great for ATSC3.0/AC4 streams in the greater Phoenix area. For those who want to run the binaries outside of the MSYS2 shell, you will need to copy the following DLL files to the folder where your ffmpeg binaries ultimately reside.
....
I've been watching the ffmpeg feature request 8349 and your comments there. It isn't clear to me what the state is of that request. It seems there's a proof of concept but it isn't clear if what has been done so far is going to be accepted into the next release of ffmpeg or if they devs are going to hold out for more functionality.

What do you think?

airwedge1
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Re: AC-4 Audio?

Post by airwedge1 »

I'm a bit confused by dolby ac-4 / dolby atmos. No receivers or sound bars explicitly say dolby ac-4. But the internet says they are different. Text below.

Will sound bar / receiver need to be upgraded to support ac-4? If the receiver says dolby atmos does that mean it will be able to play dolby ac-4 / atsc 3.0 sound. Will a device like a tv or streaming device transcode the dolby ac-4 to change to a format that the receiver can accept if the receiver does not support natively?

Dolby AC-4 describes the underlying audio technology including the audio compression technology, metadata support and system aspects. Dolby Atmos describes Dolby's immersive audio experience that can be delivered by multiple Dolby audio technologies including Dolby AC-4 and Dolby Digital Plus.

ferrellsl
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Re: AC-4 Audio?

Post by ferrellsl »

ferrellsl wrote: Thu Jan 14, 2021 5:44 pm I completed a successful MSYS2 x64 build of ffmpeg that supports AC-4 audio streams and everything is working great for ATSC3.0/AC4 streams in the greater Phoenix area. For those who want to run the binaries outside of the MSYS2 shell, you will need to copy the following DLL files to the folder where your ffmpeg binaries ultimately reside.

They are:
libbz2-1.dll
libiconv-2.dll
libintl-8.dll
liblzma-5.dll
libstdc++-6.dll
libwinpthread-1.dll
libzstd.dll
SDL2.dll
zlib1.dll

On my system these DLL's are located in: C:\msys64\mingw64\bin

For those who want to conduct their own build, you can get the source for the AC-4/WIP here: https://github.com/richardpl/FFmpeg/tree/ac4

For those who don't want to build from source, you can download the Windows binaries from my DropBox account here: ​https://www.dropbox.com/s/eene7ecard5xk ... 4.zip?dl=1

An example command to play channel 161.1 here in Phoenix follows: C:\ffmpeg\bin>ffplay -i "http://192.168.2.142:5004/auto/v161.1?transcode=native" -ac 4
Substitute the IP address above with the correct IP address for your HD Homerun Tuner.


Enjoy!

Just a small update. For those who used my binaries and experienced stuttering video and the VQ dropping to 0 after a few minutes of streaming an ATSC3.0 channel, add the "-sync video" and infinite buffer switches to your script or command line. I.e.: ffplay.exe -i "http://192.168.2.142:5004/auto/v161.1?transcode=native" -infbuf -sync video

I also updated the binaries for x86_64. The download link has been updated to reflect the new binaries.
Last edited by ferrellsl on Mon Jan 18, 2021 8:17 pm, edited 1 time in total.

ebo
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Re: AC-4 Audio?

Post by ebo »

ferrellsl wrote: Thu Jan 14, 2021 5:44 pm For those who don't want to build from source, you can download the Windows binaries from my DropBox account here: https://www.dropbox.com/s/eene7ecard5xk ... 4.zip?dl=0
I tried to download from that link but all I got was a blank page. So I changed ?dl=0 to ?dl=1 and that gave me the download. Was that the right thing to do?

ferrellsl
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Re: AC-4 Audio?

Post by ferrellsl »

ebo wrote: Mon Jan 18, 2021 4:45 pm
ferrellsl wrote: Thu Jan 14, 2021 5:44 pm For those who don't want to build from source, you can download the Windows binaries from my DropBox account here: https://www.dropbox.com/s/eene7ecard5xk ... 4.zip?dl=1
I tried to download from that link but all I got was a blank page. So I changed ?dl=0 to ?dl=1 and that gave me the download. Was that the right thing to do?
Yes, glad that worked for you. I should have tested that link before posting it but it was generated by DropBox so I assumed it was a good link! LOL! I went ahead and updated the links in my previous posts with a "1" and tested them and they work now. Thanks for catching that.

ferrellsl
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Re: AC-4 Audio?

Post by ferrellsl »

kohaiut wrote: Sat Jan 16, 2021 2:03 pm
ferrellsl wrote: Thu Jan 14, 2021 5:44 pm I completed a successful MSYS2 x64 build of ffmpeg that supports AC-4 audio streams and everything is working great for ATSC3.0/AC4 streams in the greater Phoenix area. For those who want to run the binaries outside of the MSYS2 shell, you will need to copy the following DLL files to the folder where your ffmpeg binaries ultimately reside.
....
I've been watching the ffmpeg feature request 8349 and your comments there. It isn't clear to me what the state is of that request. It seems there's a proof of concept but it isn't clear if what has been done so far is going to be accepted into the next release of ffmpeg or if they devs are going to hold out for more functionality.

What do you think?
Well, I'd expect the maintainers to integrate the AC-4 code into the trunk once enough people have built and tested richardpl's code without issues. Then it's up to richardpl to ask the maintainers to conduct a pull request integrating his code into the ffmpeg trunk. It doesn't seem like there have been many people building/testing his branch at this point in time but I would expect that as ATSC3.0/AC-4 gains wider adoption that more coders will build and test his WIP. How long it will be before it gets mainlined is anybody's guess. I'm just glad we have a working solution at the moment. Folks should probably make a donation to richardpl for the time and effort he put into this WIP.

I'd also add that his code is more than just a proof-of-concept. It builds fine and works fine too.

Lost Dog
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Re: AC-4 Audio?

Post by Lost Dog »

I was able to compile Kodi 18.9 against the ffmpeg AC-4 branch. Playing ATSC 3.0 stream captures from the PDX market worked well and audio seemed find. I cannot confirm if it was correct channel 5.1 because this was being done on my desktop rather than HTPC (headphone only on my desktop).

Live TV was really buggy however. Many times it froze when trying to tune an ATSC 3.0 station but I suspect that's due to the plugins and not the ffmpeg. When it did manage to tune it seemed to play fine with audio.

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