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Adaptive Multi Rate – Wideband Plus (AMR-WB+) codec was standardized by 3GPP in the year 2004. The codec operates on speech and audio signals sampled at 8 - 48 KHz and generates compressed bit-streams with bit-rates ranging from 6 to 36 kbps for mono and 8 to 48 kbps for stereo signals respectively. It uses a hybrid coding approach that combines the strength of speech and audio codecs. When compared with audio codecs, it performs better for speech and mixed (speech and audio) content type input signals. Internally, the codec operates at a nominal sampling frequency of 25.6 KHz. Gradual bit rate and bandwidth scaling is achieved by scaling the internal sampling frequency from 0.5 to 1.5 times the nominal sampling frequency. Correspondingly, it provides an audio bandwidth that ranges from 6.4 KHz (lowest bit-rate) to 19.2 KHz (highest bit-rate). The encoder has a low-complexity option for implementation on terminal devices and the decoder has an inherent packet loss concealment mechanism. The principal applications for this codec include low bit-rate multimedia services such as music, speech, news, sportscasts, weather, movies, audio books, training, person-to-person MMS, commercials etc. on mobile networks.
Salient features (of CouthIT implementation):
Based on 3GPP specification
Optimized ASM/C implementation
Support for bitrates ranging from 6 – 36 kbps for mono and 8 – 48 kbps for stereo.
Support for RAW, FSF, TIF, IF1, IF2, and MMS bit-stream formats.
Supports integrated Packet Loss Concealment (PLC) algorithm.
Optional support for xDM APIs.
Little- and big-endian implementation on ARM
Option for limiter flag to smooth the output signal and avoid clipping.
Option to force output to mono
Option to specify the sampling frequency of the output PCM samples (8 – 48 KHz)
Scope of Testing:
Bit-exact with the standard test vectors
Module is fully interruptible.
Tested for any illegal memory access by the module.
Tested for compliance with register preservation requirements
Tested for Input buffer corruption
Tested for I/O buffer alignment requirements
Tested for multi-instance implementation
Tested for 100% code coverage
Range validation for all the API parameters
Tested for Packet loss conditions with 5% loss to 25% loss
ARM implementation validated on OMAP3530 (Cortex-A8) and DM6446/DM6467 (ARM926EJ-S) platforms.
The product is ready for evaluation.
For most current information on the performance specifications and availability of the implementation on various ARM cores, please send in your enquiry to email@example.com