4 ms·

I'm a co-maintainer of this project. If anyone has questions, I'd be happy to answer them.

by argilo 3y ago

geerlingguy 3y ago
No questions, just thanks so much for maintaining it! Back in 2019 the project enabled me to listen to the local baseball team's broadcasts [1] without a traditional radio since their online streams were restricted due to MLB's dumb blackout rules. [1] https://www.jeffgeerling.com/blog/2019/hospital-stay-and-mlb-blackouts-led-me-rtl-sdr-radio https://www.jeffgeerling.com/blog/2019/hospital-stay-and-mlb...
- argilo 3y ago
  I'm happy to hear you found it useful!
wg0 3y ago
What dongles and antennas are recommended. Asking as a noob always fascinated by SDR. Also, is SDR computationally expensive?
- argilo 3y ago
  My preferred dongle is the RTL-SDR Blog V3: https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/ https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/ They also have a new V4 version, but it requires updated drivers that will take a bit of time to percolate out to Linux distributions and the like. NooElec also has a line of RTL-SDR dongles that I would recommend: https://www.nooelec.com/store/sdr/sdr-receivers.html https://www.nooelec.com/store/sdr/sdr-receivers.html The best antenna will depend on what you're trying to receive. Different antennas are optimized for different frequency ranges, and may be either omnidirectional (receiving equally well from many directions) or favour reception in one particular direction. To get started, you could buy a dongle that comes with an antenna included, but you may eventually want to switch to something targeted to the particular application you have in mind. As for the computational cost, it depends a lot on what you're trying to do. As a general rule, the wider the bandwidth of the signal, the more processing power it will take to demodulate. HD Radio is relatively narrow-band (400 kHz), so it doesn't require much CPU power to receive it.
  - cf100clunk 3y ago
    FM Band and TV antennae are easy to DIY, and you'll find loads of great leading and bleeding edge designs and plans online at forums like this: https://www.digitalhome.ca/forums/antenna-research-development.186/ https://www.digitalhome.ca/forums/antenna-research-developme...
westurner 3y ago
Would it be feasible to do something similar with OpenWRT opkg packages to support capturing weather radar (and weather forecasts and alerts?) data from digital FM radio with a USB RTL-SDR radio? Python apps require a bunch of disk space, which is at a premium on low-wattage always-on routers. OpenWRT's luci-app-statistics application supports rrdtool and collectd for archived stats over time (optionally on a USB stick or an SSD instead of the flash ROM of the router, which has a max lifetime in terms of number of writes) https://github.com/openwrt/luci/tree/master/applications/luci-app-statistics https://github.com/openwrt/luci/tree/master/applications/luc... From https://news.ycombinator.com/item?id=38138230 https://news.ycombinator.com/item?id=38138230 : > LuCI is the OpenWRT web UI which is written in Lua; which is now implemented mostly as a JSON-RPC API instead of with server-side HTML templates for usability and performance on embedded devices. [...] Notes on how to write a LuCI app in Lua:
- argilo 3y ago
  It might be possible, but I'm not sure whether a typical router would have enough CPU horsepower to do the processing required to demodulate the signal.
  - westurner 3y ago
    What models of Raspberry Pi are sufficient, or how many Mhz and RAM are necessary to demodulate an HD radio stream? (Pi Pico, Pi Zero, and Pi A+/B+/2/3/4 have 2x20 pin headers for HATs. Orange Pi 5 Plus has hardware H.265 encoding with hw-enc and gstreamer fwiu.)
    - argilo 3y ago
      I haven't investigated the CPU and RAM requirements in depth, but I have used nrsc5 on a Pi 3B without issue. I suspect a Pi Pico would be too small.
- argilo 3y ago
  Also, I should mention that Python is not a requirement. The GUIs that people have created so far were written in Python, but the nrsc5 project itself is built entirely in C, and it exposes a C API.
myself248 3y ago
Have you ever found interesting/unexplained data in the packet streams? I know there's provision for traffic stuff in there, and a few other defined types, but what else is hiding? Reason I ask, is analog FM had all sorts of sideband streams for the longest time, like SCA audio and DirectBand digital, that weren't well known at the time. And while internet access is certainly easier to get these days, there might still be a justification for one-way data broadcasts in certain applications, so I wonder if someone's out there leasing subchannels or sub-packet-IDs or what-not, and shuffling encrypted data around in them.
- argilo 3y ago
  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 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.
  - argilo 3y ago
    Also, all of those stream types seem to be used across multiple stations. I haven't seen any weird one-off streams.
- patja 3y ago
  There was the somewhat recent issue in Seattle where a station included an image file with no file extension, and it bricked the radios in Mazdas: https://arstechnica.com/cars/2022/02/radio-station-snafu-in-seattle-bricks-some-mazda-infotainment-systems/ https://arstechnica.com/cars/2022/02/radio-station-snafu-in-...
anonymousiam 3y ago
Awesome project! I hope it doesn't get taken down by DTS! Here's my question: Was there a reason for not using the GNU Radio framework for this project? https://www.gnuradio.org https://www.gnuradio.org Thanks!
- argilo 3y ago
  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 https://github.com/theori-io/nrsc5/pull/131 for an earlier experiment with that.)
fooblaster 3y ago
What documentation did you use to decode hd radio protocol? From what I recall, the formats were all closed in some capacity. Did you reverse engineer it?
- argilo 3y ago
  Most of the details are available in the specification, which is available here: https://www.nrscstandards.org/standards-and-guidelines/documents/standards/nrsc-5-e/nrsc-5-e.asp https://www.nrscstandards.org/standards-and-guidelines/docum... The missing parts are the audio codec (HDC) and the formats of the various data streams. These have required reverse engineering.
  - fooblaster 3y ago
    oh I thought it was closed. Thanks for the pointer.
  - fooblaster 3y ago
    Did you take any notes on the reverse engineering or is your code the documentation?
    - argilo 3y ago
      The code of nrsc5 (and my transmitter project, https://github.com/argilo/gr-nrsc5 https://github.com/argilo/gr-nrsc5) would be the best source of information for the undocumented parts. I do have some private notes, but the useful information has already gone into the code.
donatj 3y ago
What would it take to get this functionality merged into Cubic or Gqrx?
- argilo 3y ago
  I am also the maintainer of Gqrx and I would love for it to have a built-in NRSC-5 receiver. The trouble is that some aspects of NRSC-5 are still patent-encumbered, which makes software distribution problematic. For that reason, nrsc5 is only provided in source form today. The situation may change once the relevant patents have expired.
  - donatj 3y ago
    Thank you for the hard work! Gqrx allowed me to identify the "Alternate Frequency" flag on one of my favorite FM stations that was causing my car to change channel every couple minutes. I was actually able to contact the station and they fixed it! https://www.radiodiscussions.com/threads/kqrs-rdbs-alternate-frequency-issue.745697/ https://www.radiodiscussions.com/threads/kqrs-rdbs-alternate... Ooh, since I have your ear, Gqrx performance is pretty unusable on my Apple Silicon Mac, like 1-2 FPS rendering the charts and the whole UI chugs. It was fine on my Intel Mac. There any work going into that? I fully understand if it's a QT UI toolkit issue and out of your hands.
    - argilo 3y ago
      There's an issue open for this: https://github.com/gqrx-sdr/gqrx/issues/1104 https://github.com/gqrx-sdr/gqrx/issues/1104 I could really use some help from a software build expert. Gqrx and all its dependencies would need to be built in CI with Apple silicon support, and I don't know how to do that.

I'm a co-maintainer of this project. If anyone has questions, I'd be happy to answer them.

by argilo 3y ago

I'm a co-maintainer of this project. If anyone has questions, I'd be happy to answer them.

No questions, just thanks so much for maintaining it! Back in 2019 the project enabled me to listen to the local baseball team's broadcasts [1] without a traditional radio since their online streams were restricted due to MLB's dumb blackout rules. [1] https://www.jeffgeerling.com/blog/2019/hospital-stay-and-mlb-blackouts-led-me-rtl-sdr-radio https://www.jeffgeerling.com/blog/2019/hospital-stay-and-mlb...

argilo 3y ago
I'm happy to hear you found it useful!

wg0 3y ago

What dongles and antennas are recommended. Asking as a noob always fascinated by SDR. Also, is SDR computationally expensive?

argilo 3y ago
My preferred dongle is the RTL-SDR Blog V3: https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/ https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/ They also have a new V4 version, but it requires updated drivers that will take a bit of time to percolate out to Linux distributions and the like. NooElec also has a line of RTL-SDR dongles that I would recommend: https://www.nooelec.com/store/sdr/sdr-receivers.html https://www.nooelec.com/store/sdr/sdr-receivers.html The best antenna will depend on what you're trying to receive. Different antennas are optimized for different frequency ranges, and may be either omnidirectional (receiving equally well from many directions) or favour reception in one particular direction. To get started, you could buy a dongle that comes with an antenna included, but you may eventually want to switch to something targeted to the particular application you have in mind. As for the computational cost, it depends a lot on what you're trying to do. As a general rule, the wider the bandwidth of the signal, the more processing power it will take to demodulate. HD Radio is relatively narrow-band (400 kHz), so it doesn't require much CPU power to receive it.
- cf100clunk 3y ago
  FM Band and TV antennae are easy to DIY, and you'll find loads of great leading and bleeding edge designs and plans online at forums like this: https://www.digitalhome.ca/forums/antenna-research-development.186/ https://www.digitalhome.ca/forums/antenna-research-developme...

westurner 3y ago

Would it be feasible to do something similar with OpenWRT opkg packages to support capturing weather radar (and weather forecasts and alerts?) data from digital FM radio with a USB RTL-SDR radio? Python apps require a bunch of disk space, which is at a premium on low-wattage always-on routers. OpenWRT's luci-app-statistics application supports rrdtool and collectd for archived stats over time (optionally on a USB stick or an SSD instead of the flash ROM of the router, which has a max lifetime in terms of number of writes) https://github.com/openwrt/luci/tree/master/applications/luci-app-statistics https://github.com/openwrt/luci/tree/master/applications/luc... From https://news.ycombinator.com/item?id=38138230 https://news.ycombinator.com/item?id=38138230 : > LuCI is the OpenWRT web UI which is written in Lua; which is now implemented mostly as a JSON-RPC API instead of with server-side HTML templates for usability and performance on embedded devices. [...] Notes on how to write a LuCI app in Lua:

argilo 3y ago
It might be possible, but I'm not sure whether a typical router would have enough CPU horsepower to do the processing required to demodulate the signal.
- westurner 3y ago
  What models of Raspberry Pi are sufficient, or how many Mhz and RAM are necessary to demodulate an HD radio stream? (Pi Pico, Pi Zero, and Pi A+/B+/2/3/4 have 2x20 pin headers for HATs. Orange Pi 5 Plus has hardware H.265 encoding with hw-enc and gstreamer fwiu.)
  - argilo 3y ago
    I haven't investigated the CPU and RAM requirements in depth, but I have used nrsc5 on a Pi 3B without issue. I suspect a Pi Pico would be too small.
argilo 3y ago
Also, I should mention that Python is not a requirement. The GUIs that people have created so far were written in Python, but the nrsc5 project itself is built entirely in C, and it exposes a C API.

myself248 3y ago

Have you ever found interesting/unexplained data in the packet streams? I know there's provision for traffic stuff in there, and a few other defined types, but what else is hiding? Reason I ask, is analog FM had all sorts of sideband streams for the longest time, like SCA audio and DirectBand digital, that weren't well known at the time. And while internet access is certainly easier to get these days, there might still be a justification for one-way data broadcasts in certain applications, so I wonder if someone's out there leasing subchannels or sub-packet-IDs or what-not, and shuffling encrypted data around in them.

argilo 3y ago
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 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.
- argilo 3y ago
  Also, all of those stream types seem to be used across multiple stations. I haven't seen any weird one-off streams.
patja 3y ago
There was the somewhat recent issue in Seattle where a station included an image file with no file extension, and it bricked the radios in Mazdas: https://arstechnica.com/cars/2022/02/radio-station-snafu-in-seattle-bricks-some-mazda-infotainment-systems/ https://arstechnica.com/cars/2022/02/radio-station-snafu-in-...

anonymousiam 3y ago

Awesome project! I hope it doesn't get taken down by DTS! Here's my question: Was there a reason for not using the GNU Radio framework for this project? https://www.gnuradio.org https://www.gnuradio.org Thanks!

argilo 3y ago
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 https://github.com/theori-io/nrsc5/pull/131 for an earlier experiment with that.)

fooblaster 3y ago

What documentation did you use to decode hd radio protocol? From what I recall, the formats were all closed in some capacity. Did you reverse engineer it?

argilo 3y ago
Most of the details are available in the specification, which is available here: https://www.nrscstandards.org/standards-and-guidelines/documents/standards/nrsc-5-e/nrsc-5-e.asp https://www.nrscstandards.org/standards-and-guidelines/docum... The missing parts are the audio codec (HDC) and the formats of the various data streams. These have required reverse engineering.
- fooblaster 3y ago
  oh I thought it was closed. Thanks for the pointer.
- fooblaster 3y ago
  Did you take any notes on the reverse engineering or is your code the documentation?
  - argilo 3y ago
    The code of nrsc5 (and my transmitter project, https://github.com/argilo/gr-nrsc5 https://github.com/argilo/gr-nrsc5) would be the best source of information for the undocumented parts. I do have some private notes, but the useful information has already gone into the code.

donatj 3y ago

What would it take to get this functionality merged into Cubic or Gqrx?

argilo 3y ago
I am also the maintainer of Gqrx and I would love for it to have a built-in NRSC-5 receiver. The trouble is that some aspects of NRSC-5 are still patent-encumbered, which makes software distribution problematic. For that reason, nrsc5 is only provided in source form today. The situation may change once the relevant patents have expired.
- donatj 3y ago
  Thank you for the hard work! Gqrx allowed me to identify the "Alternate Frequency" flag on one of my favorite FM stations that was causing my car to change channel every couple minutes. I was actually able to contact the station and they fixed it! https://www.radiodiscussions.com/threads/kqrs-rdbs-alternate-frequency-issue.745697/ https://www.radiodiscussions.com/threads/kqrs-rdbs-alternate... Ooh, since I have your ear, Gqrx performance is pretty unusable on my Apple Silicon Mac, like 1-2 FPS rendering the charts and the whole UI chugs. It was fine on my Intel Mac. There any work going into that? I fully understand if it's a QT UI toolkit issue and out of your hands.
  - argilo 3y ago
    There's an issue open for this: https://github.com/gqrx-sdr/gqrx/issues/1104 https://github.com/gqrx-sdr/gqrx/issues/1104 I could really use some help from a software build expert. Gqrx and all its dependencies would need to be built in CI with Apple silicon support, and I don't know how to do that.