w1700k-stream

w1700k-stream [--bind IP] [--port N] [options]

w1700k-stream is the host's one receiver of the W1700K's UDP IQ export. It puts datagrams in order, unpacks them, and serves complex int16 IQ to every consumer on the host through a POSIX shared-memory object (default `/w1700k-stream`, visible as `/dev/shm/w1700k-stream`). w1700k-spectrum, sdr-recv, or any program that maps the ring attaches as a consumer. A second process bound to the same UDP port would steal half the datagrams, so consumers read the ring instead of opening another socket.Each export datagram is one 8 KiB DMA completion: a 16-byte header (magic `0x31524453` "SDR1", offset, slice bytes, sequence) plus a slice of 2048 complex samples. Raw slices are 8192 bytes (14-bit I/Q packed in 32-bit words); at 320 Msps half the slices are packed to 7168 bytes (lossless). Completions are filed by sequence into a reorder ring and published in order. A missing completion becomes a loss after 1024 newer ones arrive without it.On request it also flattens the stream: a 129-tap linear-phase FIR that inverts the radio's decimation roll-off in the samples themselves, so every consumer sees the corrected stream. Flatten applies when a consumer sets the control word and the analog filter is as wide as the sample rate (not 640/2, which is already flat).Build with a C++17 compiler and single-precision FFTW3 (`make` in `host/stream`). The published interface is `include/w1700k_stream.h`.

--bind IP

Stream destination address on this host (default 10.77.0.10).

UDP port (default 7700).

UDP sockets and receive threads with `SO_REUSEPORT` (default 8). The unit spreads its source ports across them.

Threads that unpack and correct (default 6).

Shared ring size in MiB, a power of two (default 512; about 0.42 s at 320 Msps).

Shared-memory object (default `/w1700k-stream`).

Print a JSON status line on stdout every S seconds (default 0, off).

The 10 GbE destination needs an MTU of at least 8236 and room for 48 MiB socket buffers (`sysctl -w net.core.rmemmax=67108864`); otherwise the kernel caps buffers silently and drops datagrams (`socketdrops`). One service owns the port. A second service under the same shared-memory name refuses to start; at exit the object is unlinked.The service is built from the W1700K SDR tree; it is not a typical distro package. It does nothing useful without w1700k starting a stream on a provisioned unit.

Part of W1700K SDR (host stream service under `host/stream`). It replaced per-consumer UDP receivers so one process owns the 10 GbE import and every tool on the host shares the same ordered, optionally flattened IQ ring.

w1700k(1), w1700k-spectrum(1), sdr-recv(1), rtl_sdr(1), gqrx(1)

Source code · Documentation