nrsc5

That decision was made by the original author (Andrew Wesie), but I think it makes sense because nrsc5 only needs a tiny fraction of the functionality that GNU Radio provides. Implementing the functionality directly in nrsc5 avoids the need for a large and complex dependency. One downside is that we don't get the broad hardware support that GNU Radio provides, but maybe we'll someday take another crack at integrating SoapySDR. (See https://github.com/theori-io/nrsc5/pull/131 for an earlier experiment with that.)

Some stations have "HD TMC" (traffic message channel) streams. The others that I've encountered are "HERE Images" (traffic & weather radar images, discussed and mostly reverse engineered in https://github.com/theori-io/nrsc5/pull/308), "HERE TPEG", "TTN TPEG", "TTN STM", "NavteqAdmin" and "NavteqPacketData1." At present, nrsc5 makes these streams available through its API, but doesn't otherwise do anything useful with them. I don't believe any of the GUIs process them either. Some reverse engineering work is needed.

In addition to files, some stations also send out "stream" and "packet" data. There is ongoing work to reverse engineer the formats. See the discussion here for details: https://github.com/theori-io/nrsc5/pull/308

Goatse other people's radios is a terrible idea. Advanced data services provide broadcasters with the ability to transmit information that may be unrelated to MPS, SIS or SPS. These services can carry any form and content that can be expressed as a data file or a data stream, including audio services. Examples of such services include (i) visual effects associated with MPS, SIS, or SPS services; (ii) multimedia presentations of stock, news, weather, and entertainment programming including audio, text and images; (iii) broadcast updates to in-vehicle systems; (iv) local storage of content for time shifting and later replay; (v) targeted advertising; (vi) traffic updates and information for use with navigation systems; and (vii) subscription or free-but-limited-access services using conditional access. https://www.nrscstandards.org/standard

HD Radio is closed and proprietary, but there is at least one FOSS receiver out there: https://github.com/theori-io/nrsc5 The protocol itself is actually standardized: https://www.nrscstandards.org/standards-and-guidelines/docum... It's just the audio codec that's proprietary, but it's basically just a slightly modified version of AAC so it's been decoded.

All-digital AM is an accepted, but not widely-used, standard. It could make the AM broadcast band better suited for music and performance, instead of just talk. As far as I know, WWFD-AM radio, 820 kHz, based in Frederick MD, is the only fully digital AM broadcast radio station in the US. A radio amateur based in Mayland or Washington DC, using SDR techniques, would be well-placed to make an I/Q recording of WWFD and share it so that the rest of us can study the format. Here is something to shoot for: - record I/Q samples (not Q-branch), so that signal structure and phase information is preserved - from on-air digital WWFD-AM, not the repeater on WWFD-FM - preferably a recording that crosses the top of an hour (includes a time hack and station call) - sample passband of 22 kHz centered on 820 kHz (809-831 kHz) or wider (captures adjacent

It's been cracked. Here's a receiver for RTL-SDR. https://github.com/theori-io/nrsc5 And a transmitter for GNU Radio. https://github.com/argilo/gr-nrsc5

This is an excellent write up of the first software based HD Radio receiver. It is licensed GPLv3 and on Github at https://github.com/theori-io/nrsc5