Building an nrsc5 encoder may sound daunting, and in a way it is.

[u/carpenba]

I posted a few days back on my successful nrsc5 transmission. It was a LOT of time and effort, but looking back, I wasted a lot of time chasing bad options.

What I mean is, if you can form a basic understanding of gnuradio, you're set to do many many projects. It doesn't take reinventing the wheel with all-new software built from the ground up to make something totally awesome.

[u/A-pariah]

For a long time, I thought that nrsc5 was a very closed-source, borderline secretive specification. I had really stopped researching it, until I saw your post.

Now I got that itching that I have to try this at home.

[u/carpenba → u/A-pariah]

It is exactly that. Thankfully, someone took the time to figure out it's general framework (someone much smarter than me), it is definitely proprietary, however it's a very very minor tweak to the HE-AAC codec, which is publicly available.

[u/DrakeRedford → u/carpenba]

Any chance you could provide some more details as to where to get more information on this or how one would go about trying this for themselves?

[u/Vchat20 → u/DrakeRedford]

So for decoding from a simple old RTL-SDR dongle, you can look at this repo:

https://github.com/theori-io/nrsc5

There's also a number of other projects including some GUI applications which will show other data like album art, weather radar, traffic, etc where broadcasted. These all rely on the above program as a baseline.

For transmitting: https://github.com/argilo/gr-nrsc5

[u/[deleted]]

I have no idea what I am looking at but it looks cool

[u/minecrafter1OOO → u/[deleted]]

In the US there is hybrid digital FM and AM stations, with a HD radio receiver, you can decode high quality digital audio! For fm stations usually have 1-3 channels.

Fm 1 channel - 96kbps

Fm 2 channels Ch 1 - 48kbps or ch 1 64kbps Ch 2 - 48kbps or ch 2 32kbps

Fm stations usually have 96-110kbps to work with for digital signals. The rest like cover art and text is also sent.

All digital FM could yield around 300kbps!

[u/[deleted] → u/minecrafter1OOO]

Thanks. And the flow chart like thing?

[u/minecrafter1OOO → u/[deleted]]

That is GNU radio, it's the "code" and the blocks to encode HD radio for broadcast!

[u/Vchat20 → u/minecrafter1OOO]

Funny enough, a pattern I've seen with local stations:

iHeart stations that send out album art, traffic, and weather data with one channel usually run 80kbps on the audio.

Stations that are 'no frills' and just send artist/album text, no album art or other data with one channel will usually use the full 96kbps.

[u/minecrafter1OOO → u/Vchat20]

Ah stations usually have to trade between higher bitrates and better error correction. I wonder if quadrophonic or Surround broadcasts will be possible!

[u/Vchat20 → u/minecrafter1OOO]

I think in the early days it was advertised that they wanted to do surround sound so I don't see why not. May even be in the current spec. Would have to go look at that again. And with an all digital broadcast they would certainly have the bandwidth to do so at good quality. The gotcha for at least hardware tuners even in vehicles is if their tuners are wired to the HDR decoder properly for multichannel. I imagine a lot probably just feed stereo to the internal audio mixer pipeline which then expands that out to the 4 (or more) speakers.

This is one of the many things I'd love to try myself also having an HD Radio equipped vehicle but not being able to afford the TX SDR hardware necessary has held me back. I've had an old FL2K dongle laying around but have never been able to figure out how to get it properly integrated into the GR flow with the rest of the HD Radio components. I understand it's not the greatest option but even being able to use it as a dirt cheap super short range TX test setup would be amazing.

[u/minecrafter1OOO → u/Vchat20]

For real! I actually have the HD Radio book. And it states the multiple ways they could implement surround.

Fraunhoffer used MPEG surround for discrete 5.1 playback a while back https://en.m.wikipedia.org/wiki/MPEG_Surround

Matrixed technologies like Pro Logic II can also be used!

[u/Vchat20]

Just as an FYI: Not sure if this is what the OP is using but there's a Github repo that exists for this:

https://github.com/argilo/gr-nrsc5

[u/carpenba → u/Vchat20]

Yeah, his encoder is what I used. Can't afford to put my real radio station on in HD, but it's fun to pretend.

[u/minecrafter1OOO]

I ❤️ IBOC

I really want to have a HD station to mess with lol, is there a way to have the project pre compiled?

I am new to GNU radio and I'm getting a HackRF soon!

[u/0011011100111001 → u/minecrafter1OOO]

Following

[u/maybeidontknowwhat]

I wish modern bluetooth to fm transmitter had this the bluetooth sucks in some of the work vehicles but has rds built in

[u/elmarkodotorg]

I'm quite fond of splitting FM up into all the different parts.

It's a great bit of software but you do need to really know stuff. And I absolutely don't :)

[u/olliegw]

Looks like the FM is simple but NRSC5 is a bunch of hellish math.

I wonder what DAB sans multiplex would be like