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Speex: a free codec for free speech

Codec Quality Comparison

Warning: these are machine-generated results (not from real listeners) and hence should be taken with a grain of salt.

Codec Feature Comparison

Codec Rate (kHz) bitrate (kbps) delay frame+lookahead (ms) multi-rate embedded VBR PLC bit-robust license
Speex 8, 16, 32 2.15-24.6 (NB)
4-44.2 (WB)
20+10 (NB)
20+14 (WB)
yes yes yes yes open-source/
free software
iLBC 8 15.2 or 13.3 20+5 or 30+10 yes no charge, but not open-source
AMR-NB 8 4.75-12.2 20+5? yes yes yes proprietary
AMR-WB
(G.722.2)
16 6.6-23.85 20+5? yes yes yes proprietary
G.722.1 (Siren7) 16 (16) 24, 32 20+20 yes yes yes no charge, but not open-source
G.729 8 8 10+5 yes yes proprietary
GSM-FR 8 13 20+? ? ? patented?
GSM-EFR 8 12.2 20+? yes yes proprietary
G.723.1 8 5.3 6.3 37.5 yes ? proprietary
G.728 8 16 0.625 proprietary
G.722 16 48 56 64 ? yes ? ?

Definitions

multi-rate
Allows the codec to change bitrate dynamically, at any moment
embedded
A codec that embeds narrowband bitstreams in wideband bitstreams
VBR
Variable bitrate
PLC
Packet loss concealment
bit-robust
Robust to corruption at the bit level, as found on wireless networks

Special Features

Speex
Speex supports intensity stereo encoding and 32 kHz sampling
iLBC
iLBC frames are encoded completely independently; while this provides better quality when 10% (or more) of the packets are being dropped, this makes the codec suboptimal for clean line conditions.