Audio codecs

Name standardized by description bit rate (kb/s) sampling rate (kHz) frame size (ms) remarks
(ADPCM) DVI Intel, IMA ADPCM 32 8 sample
G.711 ITU-T Pulse code modulation (PCM) 64 8 sample mu-law (US, Japan) and A-law (Europe) companding
G.721 ITU-T Adaptive differential pulse code modulation (ADPCM) 32 8 sample Now described in G.726; obsolete.
G.722 ITU-T 7 kHz audio-coding within 64 kbit/s 64 16 sample Subband-codec that divides 16 kHz band into two subbands, each coded using ADPCM
G.722.1 ITU-T Coding at 24 and 32 kbit/s for hands-free operation in systems with low frame loss 24/32 16 20 See also
G.723 ITU-T Extensions of Recommendation G.721 adaptive differential pulse code modulation to 24 and 40 kbit/s for digital circuit multiplication equipment application 24/40 8 sample Superceded by G.726; obsolete. This is a completely different codec than G.723.1.
G.723.1 ITU-T Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s 5.6/6.3 8 30 Part of H.324 video conferencing. DSP Group. It encodes speech or other audio signals in frames using linear predictive analysis-by-synthesis coding. The excitation signal for the high rate coder is Multipulse Maximum Likelihood Quantization (MP-MLQ) and for the low rate coder is Algebraic-Code-Excited Linear-Prediction (ACELP).
G.726 ITU-T 40, 32, 24, 16 kbit/s adaptive differential pulse code modulation (ADPCM) 16/24/32/40 8 sample ADPCM; replaces G.721 and G.723.
G.727 ITU-T 5-, 4-, 3- and 2-bit/sample embedded adaptive differential pulse code modulation (ADPCM) var. ? sample ADPCM. Related to G.726.
G.728 ITU-T Coding of speech at 16 kbit/s using low-delay code excited linear prediction 16 8   CELP. Annex J offers variable-bit rate operation for DCME.
G.729 ITU-T Coding of speech at 8 kbit/s using conjugate-structure algebraic-code-excited linear-prediction (CS-ACELP) 8 8 10 Low delay (15 ms)
GSM 06.10 ETSI Regular­Pulse Excitation Long­Term Predictor (RPE-LTP) 13 8 22.5 Used for GSM cellular telephony.
LPC10e (FIPS 1015) US Govt. Linear-predictive codec 2.4 8 22.5 10 coefficients.

Last updated by Henning Schulzrinne