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gr-pipe GNU Radio blocks

gr-pipe is a set GNU Radio block for using any program as a source, sink or filter by using standard I/O pipes.

Introduction

The main goals of these blocks are:

  • Fast development of new experimental blocks (no need to dig into C++ / GNU Radio internals / SWIG / Python).
  • Ability to use any programming language able to deal with standard input and output (code a block in your preferred language: C, Java, MatLab, Perl, Ruby...).

Simple interface:

The gr-pipe blocks read and write samples sequentially in their GNU Radio internal representation. The format is the same as for gr_file_source and gr_file_sink:

GNU Radio type name C Type size
Complex two C floats (I,Q) sizeof(float)*2, generally 8 bytes
Float float sizeof(float), generaly 4 bytes
Int int sizeof(int), generally 4 bytes
Short short sizeof(short), generally 2 bytes
Byte unsigned char sizeof(unsigned char), 1 byte

Since the actual size of some objects may depend on the host platform, it is recommended to use the available language definitions to get correct sizes. Most languages are also providing routines to read/write native machine C types. See examples provided in this package for some languages.

A typical source block command will produce data "forever" on its standard output, until a SIGTERM is sent by the pipe.source block to ask for normal termination. Also, in case of an exception, the pipe will be closed and a SIGPIPE will be caught.

A typical sink block command will consume data on its standard input, until end-of-file (EOF) is read, for a proper termination.

A typical filter block command will comsume data "forever" on its standard input, process it, and produce data on its standard output, until end-of-file (EOF) is read, for normal termination. Also in case of exception, SIGPIPE may be caught.

In pipe blocks, commands are executed in a /bin/sh shell, so every standard shell features are available in commands provided to blocks (variables, loops, pipes, redirection, etc...).

See examples for a "square" block implemented in C, Java, MatLab/GNU Octave, Perl and Python.

Suggestions of use:

  • Compression (gzip, lzma, ...)
  • Encryption (gpg, openssl, ...)
  • Encoding (ffmpeg, mencoder, gsm-tools, ...)
  • Debugging (od, hexdump, ...)
  • Interface to devices (aplay, arecord, pacat, parec, ...)
  • Use your own tools...

Known limitations and problems:

  • Small performance loss, due to pipe communications.
  • Small addition of latency, due to pipe buffers. (On Linux, pipe buffer capacity can be changed. See fcntl(2) F_SETPIPE_SZ).
  • Not compatible with stream tags
  • Limited to only one input and one output maximum per block (but you may use an interleaver or multiple blocks).

Building and installing gr-pipe

Installing with GNU Radio PyBOMBS

First, install PyBOMBS on your system, following the instructions at: https://github.com/gnuradio/pybombs

For example:

pip3 install --user --upgrade git+https://github.com/gnuradio/pybombs.git
pybombs auto-config
pybombs recipes add-defaults
pybombs prefix init ~/my-gnuradio

Then, install gr-pipe using the PyBOMBS recipe:

pybombs install gr-pipe

Finally, to use the gr-pipe blocks in gnuradio-companion:

source ~/my-gnuradio/setup_env.sh
gnuradio-companion

or, using the PyBOMBS command:

pybombs run gnuradio-companion

Installing manually

This procedure assumes you have development tools and GNU Radio already already installed.

git clone git://github.com/jolivain/gr-pipe.git
mkdir gr-pipe/build
cd gr-pipe/build
cmake ..
make
sudo make install

Feedback and comments are welcome !

Julien Olivain [email protected]