AC4 support for new ATSC3.0 video

Dartman

Member
OK, I got one of the 4k silicon Dust ATSC 3.0 quad tuners recently and I decided to see if my HD HomeRun app would record the video it gets from the antenna with the new AC4 audio codec. It records it in MPG format but VideoRedo can't do anything with the video or audio it has recorded probably because of the AC4 sound codec it uses. I know it's pretty brand new and licensing and all that but are they planning to add support for it sometime in the future? I can get uncompressed 1080p video right now if my station supports it and Comcast has dropped EVERYTHING to 720p to save themselves bandwidth so I can get a better quality video from the new tuner but would love to be able to edit it down and cut down the size and all that.
Almost nothing supports AC4 playback right now. Of course the HD HomeRun app does, windows 10 does to some extent, and the Shield does in their Android app.
I didn't look all over for other threads about this so I posted here and hope your looking into it. I can probably post some short captures to where ever if needed.
 

Dan203

Senior Developer
Staff member
We do not have the ability to support AC-4 at this time. None of our codec suppliers, or even ffmpeg, support it yet. We'll keep an eye on it and when we can we'll add support, but there really isn't an option for us right now.
 

Dan203

Senior Developer
Staff member
Can you send us a sample of one of these videos so we can test it out on our end?

 

Dartman

Member
Can you send us a sample of one of these videos so we can test it out on our end?

OK, got the day off so finally captured about 5 minutes of atsc 3.0 video in MPG-TS with AC4 audio under thread 134243
 

Dartman

Member
Will be interesting to see what you find out but pretty sure nothing supports AC4 yet like you said and they want a license fee to use it. I'd love to be able to edit it with something but probably by the time they actually broadcast full 4k in a few years there will be a lot more support and options for you and us.
 

Dan203

Senior Developer
Staff member
Yeah I can't even find anything that can play the sample you uploaded.

Apparently the HDHomeRun app can play it live and the beta Channels DVR app can play recordings, but nothing else I can find will actually play AC4 audio yet.
 

Dartman

Member
So far nothing I tried except Their own app, Channels, and Their app in my Shield can play it here too so no real way to edit it. There must be more to it then just the audio codec that cuases everything to either error out or only play the video. In win 7 it will play the video in their app but no audio. I'm sure I remember my win 10 pro downloading a codec update from their store and then the HD HomeRun app worked or something. Any regular HDTV captures it makes all my apps can play but not the new AC4 stuff, even VLC refuses to load and play it.
 

Dan203

Senior Developer
Staff member
I looked around for a DirectShow codec for Windows Media Player and can’t find one. There looks like there is some code waiting to be checked in to ffmpeg to add support, and VLC uses the libs from ffmpeg to play, so once that's in it should be able to play your file. But this is all relatively new. AC-4 is still under license so whoever did this likely had to reverse engineer the format, so it might not even be 100%.

Because it's under license we have to see how much it costs before we can add support. In the past an AC-3 encoder cost almost as much as VRD itself, we were only able to add it when the patent expired and it became free.
 

Dartman

Member
Well I figured the license cost could be a big impediment to actually adding support for it. I haven't found anything for free that includes it in a codec pack yet so hopefully ffmpeg adds it soon and that will probably give everyone else indirect support for it.
I guess it's a lot more efficient and I've been loving the HEVC codec that has made my captures so much smaller than before with the same quality.
I don't think HD HomeRun has any support other than being able to play back the AC4 captures, probably because it's not a huge deal for most users and they can do everything else already without them adding editing.
 

atc98092

New member
Just got a HDHomeRun Flex last night, and will be looking forward to getting support for AC-4. I'm not recording anything from the ATSC 3.0 stations yet, as JRiver doesn't yet support ATSC 3.0 either. Since the majority of my OTA recording comes from ATSC 1.0 subchannels (which are still a long ways off from switching to ATSC 3.0), I'm not in a huge hurry for VRD or JRiver to support it. Take your time and get it right. I can't live without VRD to remove commercials! :D
 
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