See INSTALL file for instruction on how to install Speex.

The Speex project aims to build an open-source patent-free voice codec. 
Unlike other codecs like MP3 and Ogg Vorbis, Speex is specially designed 
for compressing voice at low bit-rates for applications such as voice over 
IP (VoIP). In some sense, it is meant to be complementary to the Ogg 
Vorbis codec.

Although we aim at providing a patent-free codec, we strongly suggest you
have a look at patent issues if you are thinking about using Speex 
commercially. The speech coding field is a real patent minefield and
the scope and enforceability of all these patents is sometimes unclear,
not to mention that each country has different laws.

To use Speex:

% speexenc [-n or -w] input_file.sw compressed_file.spx

% speexdec compressed_file.spx output_file.sw

where -n is for narrowband (8 kHz sampling) and -w is wideband (16 kHz 
sampling).

All audio files are assumed to be raw (no header) 16-bit PCM files. To
convert a .wav file into this format:
% sox my_file.wav -t sw my_file.sw

Note that if the original sampling frequency of the wav is not 8 kHz or 16 kHz,
you will need to add "-r 8000" or "-r 16000" (without the quotes).

To create a .wav file:
% sox -t sw my_file.sw my_file.wav