PSB7280 Просмотр технического описания (PDF) - Siemens AG

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PSB7280

Joint Audio Decoder-Encoder

Siemens AG 

PSB 7280

1

Introduction

1.1

Overview

The PSB 7280 Joint Audio Decoder Encoder is a device which implements voice

compression algorithms using the Low-Delay Code Excited Linear Prediction (LD-CELP)

standard as defined in the ITU-T G.728 Recommendation, and for 7-kHz voice using the

Sub-Band Coded Adaptive Differential PCM (SBC-ADPCM) coding according to the

G.722 Recommendation. In addition G.711 PCM audio coding is also supported.

Thus in the G.728 mode it compresses a digitized PCM (64 kbit/s) or linear (128 kbit/s)

voice signal into a 16 kbit/s bit stream, and vice versa. The algorithm is implemented in

16-bit fixed point arithmetic and complies with the newest fixed point specification set

forth by the ITU.

In the G.722 mode it compresses the PCM compressed (128 kbit/s) or the linear

uncompressed (256 kbit/s) 7 kHz audio samples into a rate of 48/56/64 kbit/s, and vice

versa.

The JADE finds applications in

– ISDN Videophones (H.320)

– Video Conference Systems

– Corporate Network voice concentrators, multiplexers and gateways

– Data-over-voice and Voice-over-data terminals.

Other potential application areas are:

– Networks (e.g. LANs) for packetized voice

– Digital Added Main-Line (DAML) & Digital Circuit Multiplication Equipment (DCME)

– Voice storage e.g. in PC based applications

– Message recording and distribution.

The interfaces of the JADE allow a seamless integration into IOM-2 based systems.

After the circuit is set up in the proper mode of operation and parameter settings are

programmed by a controlling software, the circuit runs independently of the rest of the

system. Status and control information to/from the JADE can be transferred either

inband the compressed audio data via the corresponding selected interface or outband

using an 8-bit parallel host interface.

In a Videophone system using the 8 × 8 (formerly IIT) VCP (Video Codec and Multimedia

Communications Processor) the Siemens PSB 7280 can work standalone without the

need of external initialization. The default configuration of the JADE is such, that no host

is needed in this case and the full communication is done between the VCP and the

Siemens PSB 7280.

The voice compression algorithms are implemented by an embedded 16-bit fixed point

Digital Signal Processor with all memories internal and no external memory needed.

Semiconductor Group

5

Data Sheet 1998-07-01

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