About

Key features

Share available RF bandwidth between several independent clients:
- Total bandwidth can be 2016000 samples/sec at 436,600,000 hz
- One client might request 48000 samples/sec at 436,700,000 hz
- Another client might request 96000 samples/sec at 435,000,000 hz
Several clients can access the same band simultaneously
Output saved onto disk or streamed back via TCP socket
Output can be gzipped (by default = true)
Output will be decimated to the requested bandwidth
Clients can request overlapping RF spectrum
Rtl-sdr starts only after first client connects (i.e. saves solar power &etc). Stops only when the last client disconnects
MacOS and Linux (Debian Raspberrypi)

Design

Each client has its own dsp thread
Each dsp thread executes Frequency Xlating FIR Filter
Libvolk is used for SIMD optimizations
Only RTL-SDRs are supported

API

Defined in the api.h
Clients can connect and send request to initiate listening:
- center_freq - this is required center frequency. For example, 436,700,000 hz
- sampling_rate - required sampling rate. For example, 48000
- band_freq - first connected client can select the center of the band. All other clients should request center_freq within the currently selected band
- destination - "0" - save into file on local disk, "1" - stream back via TCP socket
To stop listening, clients can send SHUTDOWN request or disconnect

Queue

The data between rtl-sdr worker and the dsp workers is passed via queue. This is bounded queue with pre-allocated memory blocks. It has the following features:

Thread-safe
If no free blocks (consumer is slow), then the last block will be overriden by the next one
there is a special detached block. It is used to minimize synchronization section. All potentially long operations on it are happening outside of synchronization section.
Consumer will block and wait until new data produced

Configuration

Sample configuration can be found in tests:

https://github.com/dernasherbrezon/sdr-server/blob/main/test/resources/configuration.config

Performance

Is good. Some numbers in test/perf_xlating.c

Dependencies

sdr-server depends on several libraries:

libvolk. It is recommended to use the latest version (Currently it is 2.x). After libvolk installed or built, it needs to detect optimal kernels. Run the command volk_profile to generate and save profile.
librtlsdr. Version >=0.5.4 is required.
libconfig
libz. Should be installed in every operational system
libm. Same
libcheck for tests (Optional)

All dependencies can be easily installed from r2cloud APT repository:

sudo apt-get install dirmngr lsb-release
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys A5A70917
sudo bash -c "echo \"deb http://s3.amazonaws.com/r2cloud $(lsb_release --codename --short) main\" > /etc/apt/sources.list.d/r2cloud.list"
sudo apt-get update
sudo apt-get install libvolk2-dev librtlsdr-dev libconfig-dev check

Build

To build the project execute the following commands:

mkdir build
cd build
cmake ..
make

Install

sdr-server can be installed from r2cloud APT repository:

sudo apt-get install sdr-server

cprezzi/sdr-server