Codec Overview:
Enhanced Variable Rate Codec – Wideband (EVRC-WB or EVRC-C) was standardized by 3GPP2 in 2007. The EVRC-C codec operates on each 20ms frame of 16-bit speech signals sampled at 8 or16 KHz and generates compressed bit-stream of 171, 80, 40, or 16 bits respectively. EVRC-C splits the speech spectrum into low frequency and high frequency bands and compresses them separately. Coding of low frequency signal is based on EVRC-B standard while a LPC based coding scheme is used for the high frequency signal. It also contains a generic audio coding mode that can be used for handling non-speech signals such as music-on-hold and ring back tones. The principal applications of this codec are wideband telephony, video-telephony, gaming, streaming and ring back tones.
Salient features (of CouthIT implementation):
Based on 3GPP2 specification.
Optimized ASM/C implementation.
Re-entrant implementation.
C-callable APIs.
Operates on speech signals sampled at 8 or 16 KHz.
Support for selecting anchor operating mode or average rate mode during initialization time.
The maximum and minimum bit-rates can be configured during initialization.
The noise suppression module can be configured during initialization.
Support for dim and burst, eighth rate hangover, and null traffic frame features specified in the standard.
Supports integrated DTX mode of operation.
Support for setting the minimum and maximum DTX update interval during initialization.
Support for 8.3, 7.42, and 4.0 kbps average source encoding bit-rates.
Support for RTP payload format as specified in RFC 5188.
Support for DTMF and TTY/TDD signals as specified in the standard.
Supports integrated Packet Loss Concealment (PLC) algorithm.
Support for post-filter operation, configurable at frame boundary.
Support for decoding music signals.
Optional support for xDM APIs.
For most current information on the performance specifications and availability of developed implementation on ARM cores, please send in your enquiry to info@couthit.com