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

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
