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_profileto 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