EVRC Speech Codec

EVRC ENHANCED VARIABLE RATE SPEECH CODEC C64x

DESCRIPTION

The Adaptive Digital Technologies Enhanced Variable Rate Codec (EVRC) is a real-time implementation of the 3GPP2 standardized vocoder. The vocoder, originally developed for cellular telephony, also has other applications in VoIP. The EVRC codec encodes 8 kHz sampled voice audio signals for transmission, and compresses the signals to 8550, 4000, and 800 bits per second.

Coding Rate: 8550, 4000, and 800 bits per second

Sampling Rate: 8 kHz

Delay: 20 milliseconds

EVRC FEATURES

Functions are C-callable.
Multi–Channel Implementation.
Completely re–entrant (Channel can interrupt any Channel, any time)
The encoder and decoder meet all ITU EVRC compliance data files.
Includes Packet Loss Concealment Algorithm
Includes Support for Discontinuous Transmission (DTX)

AVAILABILITY

ADT EVRC is available on the TMS320™ DSP Family

C64x™DSP Generations

SPECIFICATIONS

EVRC C64x

All memory requirements are in units of byte.

Software	Peak Loading(MIPS)	Program Memory	Data Memory	Scratch	Per-Channel Data Memory
Preliminary	25	175 KB	15 KB	5 KB	6 KB

FUNCTIONS

EVRCENC_ADT_init    Initializes an Encode Channel

EVRCDEC_ADT_init    Initializes an Decode Channel

EVRCENC_ADT_encode    Encodes a frame of data

EVRCDEC_ADT_decode    Decodes a frame of data

APPLICATIONS

Wireless/Mobile/Personal Communications (base-stations and handset)

Voice over Packet (Gateways)

Streaming Media Servers