ASTRI

Processor
ARM ARM9E family and above with DSP extensions

Background
3GPP Adaptive Multi-Rate Narrow Band (AMR-NB) recommendation compresses linear-PCM (Pulse Code Modulated) speech input data, at a sample rate of 8kHz, to one of eight data rate modes 12 200, 10 200, 7 950, 7 400, 6 700, 5 900, 5 500 and 4 750 bps. The data rate can be run-time selectable by the user.

AMR-NB implements silence compression techniques to reduce the transmitted bit rate during silent intervals. Systems allowing discontinuous transmission (DTX) are based on Voice Activity Detection (VAD) algorithms and Comfort Noise Generator (CNG) algorithms that allow the insertion of Silence Insertion Descriptor (SID) frames during the silence intervals. There are two VAD options at the encoder.

Standard Features

•	Full conformance to 3G TS 26.074 V 6.0.0 (2004-12) including VAD1 and VAD2
•	Supported sampling frequencies (Hz): 8K
•	Bitrate scalability per channel: 12 200, 10 200, 7 950, 7 400, 6 700, 5 900, 5 500 and 4 750 bps
•	Provides mono decoding

ASTRI Specific Features

•	Provides multiple-decoder instance
•	Provides information on AMR-NB bitstream after each successful decoding frame
•	Provides infra-structure for conformance testing
•	Provides API for streaming application
•	Accepts raw 3GPP stream from MPEG-4 audio container
•	OS compatibility: Embedded Linux (Monta Vista, Candenux), Non-OS, ARM RealView
•	Memory requirements: 208KByte (Program and Data)

Performance

ASTRI ARM9E 3GPP AMR-NB decoder is optimized for the ARM9E architecture. The performance is depended on several factors of the target ARM9E platform:

•	I-Cache size
•	D-Cache size
•	SDRAM speed
•	Availability of TCM

Please make enquires on the performance for a specific ARM9E platform.