Variable cellular telephony Speech Codec
Enhanced Variable Rate Coder
- 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)
Coding Rate: 8550, 4000, and 800 bits per second
Sampling Rate: 8 kHz
Delay: 20 milliseconds
|Texas Instruments – TI TMS320C6000 C64x / C64x+/ C66x / C674x|
ADT EVRC is available on the above Platforms: Other configurations are available upon request.
NOTE: We specify MIPS (Millions of Instructions Per Second) as MCPS (Millions of Instruction Cycles Per Second). Unless otherwise specified, peak MIPS are indicated.
EVRC C6xxCPU Utilization & Memory Requirements
All Memory usage is given in units of byte.
|Software||MIPS – Peak Loading||Program Memory||Data Memory||Scratch||Per Channel Data Memory|
The Adaptive Digital Technologies Enhanced Variable Rate Coder (EVRC) is a real-time implementation of the 3GPP2 standardized vocoder. The vocoder, originally developed for cellular telephony, also has other applications in VoIP.
EVRC compresses each 20 msec of 8000 Hz, 16-bit sampled speech input into output frames of one of three different sizes: full rate – 171 bits (8.55 kbit/s), half rate – 80 bits (4.0 kbit/s), eighth rate – 16 bits (0.8 kbit/s). A quarter rate was not originally included in the EVRC specification and eventually became part of EVRC-B.
API function call summary
EVRCENC_ADT_init Initializes an Encode
ChannelEVRCDEC_ADT_init Initializes an Decode Channel
EVRCENC_ADT_encode Encodes a frame of data
EVRCDEC_ADT_decode Decodes a frame of data
Wireless/Mobile/Personal Communications (base-stations and handset)
Voice over Packet (Gateways)
Streaming Media Servers