Codec 2 is an open-source, royalty-free low-bitrate speech
vocoder created by David Rowe.1 It provides intelligible voice
from roughly 700 bps to 3200 bps and is the patent-free alternative to
AMBE-family codecs.
Codec 2 is an open, royalty-free low-bitrate speech codec — the vocoder used by M17.
How it works
Like other vocoders it models speech with pitch and spectral parameters, but its
open licence lets anyone implement it freely — the reason M17 and
the FreeDV digital-voice mode adopted it.
Relevance to SDR
Codec 2 lets fully open decoders (including M17 support) render digital voice without
proprietary vocoder licensing.
Sources
Codec 2 — Wikipedia, on the open-source royalty-free low-bitrate speech codec. ↩
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