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- Adaptive Multi-Rate Wideband Speech Codec (AMR-WB/G.722.2)
- Variable Rate Multi-Mode Wideband Speech Codec (VMR-WB)
These low-bit-rate, high-quality codecs, a breakthrough in wideband speech coding technology, increase the sampled speech spectrum to 50-7000 Hz, significantly improving the intelligibility and naturalness of speech and adding a feeling of face-to-face communication.
AMR-WB/G.722.2 consists of nine speech codec modes with bit rates of 23.85, 23.05, 19.85, 18.25, 15.85, 14.25, 12.65, 8.85 and 6.6 kbps, plus a comfort noise generation rate of 1.75 kbps. It supports dynamic adaptation to network conditions, using lower bit rates during network congestion or degradation while preserving audio quality. Built-in voice activity detection/discontinuous transmission/comfort noise generation (VAD/DTX/CNG) dramatically frees up network resources and prolongs terminal battery life. AMR-WB was standardized by ETSI/3GPP and ITU-T (as G.722.2), the first codec to be selected for both wireline & wireless services.
VMR-WB is a source-controlled, variable rate multi-mode wideband codec operating in a range from 0.8-13.3 kbps and is interoperable with AMR-WB in one mode of operation (at 12.65 kbps and below). Standardized by 3GPP2, it is the default speech codec for cdma2000® wideband telephony and multimedia streaming services.
The AMR-WB/G.722.2/VMR-WB family of codecs allows seamless interoperability across a wide range of wireless and wireline systems and platforms, reducing the need for transcoding and easing implementation of wideband applications and services. It interfaces effectively to the PSTN as well and delivers narrowband speech with improved quality. The IETF-defined RTP payload and file formats for these codecs provide robustness through enhanced error protection for the most sensitive bits within the payload, forward error correction, and packet interleaving.
Application areas for wideband speech include:
•Multimedia services for 2.5G & 3G mobile communication systems
•Wideband telephony over packet networks
•Internet applications such as:
– Broadcasting and streaming
– Chat and virtual reality immersion environments
– Multimedia realtime collaboration tools
– Narrative content archiving and distribution
– Network-based learning applications
•Digital radio broadcasting
Our off-the-shelf implementations of these key, high-quality, standard codecs are ideally suited for integration into a variety of handheld devices. Written in C or C++, a compiled implementation is available for any ARM-powered platform. Support for a variety of operating systems including Symbian, WinCE/Mobile, Linux and Palm guarantees the applicability of this turnkey solution to a broad range of manufacturers’ devices.