ITU-T G.726 Speech Coder for the TMS320C64x+ Generation

Description

The ITU-T G.726 Adaptive Differential Pulse Code Modulation (ADPCM) variable rate audio coder is widely used in applications that require robust quality with very little delay. The 8-kHz input to the encoder is either linear data or 8-bit data in A-law or Mu-law format. The output of the encoder is 2, 3, 4, or 5 bits per sample—which corresponds to data rates of 16, 24, 32, or 40 kbps.

An important feature of G.726 is that it can successfully pass signalling tones in addition to fax/modem signals. G.726 supercedes the original ITU-T G.721 and G.723 recommendations. The coder is used in many applications including videoconferencing, speech storage, telephony multiplexing, satellite communications, ISDN, and digital circuit multiplication.

Features

DSP Wizard’s G.726 implementation was designed for low resource requirements without sacrificing quality. It executes at 4.6 mips for worst-case linear data for the encoder plus the decoder. The speed does not compromise the overarching goal of conserving memory.

Highly optimized for TMS320C64x+
Supports all modes, rates, and frame sizes
Bit-exact fixed-point implementation per ITU-T test suite
Fully reentrant—self-preemptible
Multichannel
Simple integration into existing systems via C-callable functions
TI eXpressDSP compliant algorithm
Release/version 1.0
Available now
Delivered as a Zip file

Performance

G.726	Encoder	Decoder	Full Duplex
Program Code Memory (Kbytes)	4.1	4.1	4.1
Program Code Memory (Kbytes) of Linear Variant	2.9	2.9	2.9
Program Table Memory (Kbytes)	0	0	0
Data Table Memory (Kbytes)	2.4	2.4	2.4
Data Table Memory (Kbytes) of Linear Variant	0.3	0.3	0.3
Per Channel Data Memory (Kbytes)	0.1	0.1	0.2
Stack Memory (Kbytes)	0.2	0.2	0.2
Interrupt Latency (cycles)	40	40	40
Typical Call Period (ms)	10	10	10
Processor Load: Linear (MHz)	2.5	2.2	4.6
Processor Load: Mu/A Law (MHz)	2.5	2.7	5.2

A linear variant requiring 3.3 Kbytes less memory is also available.

dspwizard@dspwizard.com