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Codec 2 README
--------------

Codec 2 is an open source (LGPL 2.1) low bit rate speech codec:

    http://rowetel.com/codec2.html

Also included:

  + FDMDV modem (README_fdmdv.txt) for HF channels
  + Coherent PSK (cohpsk) for HF channels
  + FSK modem (README_fsk.txt) for VHF channels
  + an OFDM modem for HF channels (ofdm)
  + the FreeDV API - a library for embedding FreeDV in other programs

SVN Repository
--------------

Check out the latest (development branch) code using:

  $ svn co https://svn.code.sf.net/p/freetel/code/codec2-dev codec2-dev

There are unauthorised 3rd party GIT mirrors of Codec 2.

  GIT IS NOT SUPPORTED!!!

All patches, support questions etc, need to be against the SVN
repository above.

Quickstart
----------

Also see INSTALL for more general building and installing instructions. 

1/ Listen to Codec 2:

   $ cd codec2-dev
   $ mkdir build_linux
   $ cd build_linux
   $ cmake ..
   $ make
   $ ./src/c2demo ../raw/hts1a.raw hts1a_c2.raw
   $ play -t raw -r 8000 -e signed-integer -b 16 ../raw/hts1a.raw
   $ play -t raw -r 8000 -e signed-integer -b 16 ./hts1a_c2.raw

2/ Compress, Decompress and then play a file:

   using 2400 bps bit rate encoding

   $ ./src/c2enc 2400 ../raw/hts1a.raw hts1a_c2.bit
   $ ./src/c2dec 2400 hts1a_c2.bit hts1a_c2_2400.raw 

   which can be played with

   $ play -t raw -r 8000 -e signed-integer -b 16 ./hts1a_c2_2400.raw

   using 700 bps bit rate encoding

   $ ./src/c2enc 700 ../raw/hts1a.raw hts1a_c2.bit
   $ ./src/c2dec 700 hts1a_c2.bit hts1a_c2_700.raw

   which can be played with

   $ play -t raw -r 8000 -e signed-integer -b 16 ./hts1a_c2_700.raw

3/ Same thing with pipes:

   $ ./src/c2enc 1300 ../raw/hts1a.raw - | ./src/c2dec 1300 - - | play -t raw -r 8000 -s -2 -

Programs
--------
 
1/ c2demo encodes a file of speech samples, then decodes them and
saves the result.

2/ c2enc encodes a file of speech samples to a compressed file of
encoded bits.

3/ c2dec decodes a compressed file of bits to a file of speech
samples.

4/ c2sim is a simulation/development version of Codec 2.  It allows
selective use of the various Codec 2 algorithms.  For example
switching phase modelling or LSP quantisation on and off.

Debugging
---------

1/ To compile with debug symbols for using gdb:

  $ cd ~/codec2
  $ rm -Rf build_linux && mkdir build_linux
  $ cd build_linux
  $ CFLAGS=-g cmake ..
  $ make

2/ For dump file support:

  $ cd ~/codec2
  $ rm -Rf build_linux && mkdir build_linux
  $ cd build_linux
  $ CFLAGS=-DDUMP cmake ..
  $ make

Building Unit Tests
-------------------

The unittests are no longer built by default.  They require
libsamplerate and Speex.

To build them:

  $ cd ~/codec2
  $ rm -Rf build_linux && mkdir build_linux
  $ cd build_linux
  $ cmake -DCMAKE_BUILD_TYPE=Debug ..
  $ make

Directories
-----------

  cmake       - cmake support files
  octave      - Octave scripts used to support development
  script      - shell scripts for playing and converting raw files
  src         - C source code for Codec 2, FDMDV modem, COHPSK modem, FreeDV API
  raw         - speech files in raw format (16 bits signed linear 8 kHz)
  stm32       - STM32F4 microcontroller and SM1000 FreeDV Adaptor
  unittest    - unit test source code
  wav         - speech files in wave file format

Octave Packages
---------------

To run the Octave scripts the following libraries are required:

Package Name  | Version | Installation directory
--------------+---------+-----------------------
     control *|   2.6.2 | /usr/share/octave/packages/control-2.6.2
     general *|   1.3.4 | /usr/share/octave/packages/general-1.3.4
    parallel *|   2.2.0 | /usr/share/octave/packages/parallel-2.2.0
        plot *|   1.1.0 | /usr/share/octave/packages/plot-1.1.0
      signal *|   1.2.2 | /usr/share/octave/packages/signal-1.2.2
     specfun *|   1.1.0 | /usr/share/octave/packages/specfun-1.1.0

These can be installed using your systems package management system or
the Octave package management system.  The version number of each
package is not important.

FreeDV API
----------

See freedv_api.h and freedv_api.c, and the demo programs freedv_tx &
freedv_rx.  Quickstart demo using FreeDV 1600:

  $ ./freedv_tx 1600 ../../raw/hts1.raw - | ./freedv_rx 1600 - - | play -t raw -r 8000 -s -2 -q -
  $ cat freedv_rx_log.txt

FreeDV 2400A and 2400B modes
----------------------------

FreeDV 2400A and FreeDV 2400B are modes designed for VHF radio.
FreeDV 2400A is designed for SDR radios (it has a 5 kHz RF bandwidth),
however FreeDV 2400B is designed to pass through commodity FM radios.

Demos of FreeDV 2400A and 2400B:

  $ ./freedv_tx 2400A ../../raw/ve9qrp_10s.raw - | ./freedv_rx 2400A - - | play -t raw -r 8000 -s -2 -
  $ ./freedv_tx 2400B ../../raw/ve9qrp_10s.raw - | ./freedv_rx 2400B - - | play -t raw -r 8000 -s -2 -

Note for FreeDV 2400A/2400B the modem signal sample rate is 48kHz.  To
listen to the modem tones from FreeDV 2400B, or play them into a FM HT
mic input:

  $ ./freedv_tx 2400B ../../raw/ve9qrp_10s.raw - | play -t raw -r 48000 -s -2 -

Simulate FreeDV 2400B passing through a 300 to 3000 Hz audio path using sox to filter:

  $  ./freedv_tx 2400B ../../raw/ve9qrp_10s.raw - | sox -t raw -r 48000 -s -2 - -t raw - sinc 300-3000 | ./freedv_rx 2400B - - | play -t raw -r 8000 -s -2 -

Links:

  FreeDV 2400A blog post ...: http://www.rowetel.com/?p=5119
  FreeDV 2400A & 2400B demos: http://www.rowetel.com/?p=5219