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G.728 Speech Coder

G.728 Low-Delay Code Excited Linear Prediction (LD-CELP) compression has 16 kbps compression at a sampling rate of 8,000 samples per second. G.728 has an algorithmic coding delay of 0.625 ms.

Applications

Compared with G.721, G.728 tends to score worse in objective, but better in subjective testes. A characteristic of CELP algorithms is that they tend to perform poorer than ADPCM in the presence of background noise. However, G.728 has grown in popularity for video, cellular, and satellite applications since it delivers approximately the same quality voice as G.726 32 kbps while using only half the bandwidth.

Features

  • Full and half duplex modes of operation
  • Passes ITU test vectors
  • Compliant with G.728 specification
  • Optimized for high performance on leading edge DSP architectures
  • Multichannel implementation
  • Multi-tasking environment compatible

Configurations

  • DAA interface using linear codec at 8.0 kHz sample rate
  • Direct interface to 8.0 kHz PCM data stream (A-law or U-law)
  • North American/International Telephony (including caller ID) support available
  • Simultaneous DTMF detector operation available - (less than 150 hits on Bellcore test tape typical)
  • MF tone detectors, general purpose programmable tone detectors/generators available
  • Data/Facsimile/Voice Distinction available
  • Common compressed speech frame stream interface to support systems with multiple speech coders
  • Dynamic speech coders selection if multiple speech codecs available
  • Can be integrated with G.168 Echo Canceller and Tone Detection/Regeneration modules

Datasheet

ITU Recommendation G.728