G.722

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G.722

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Codec overview

G.722 speech codec was standardized by ITU-T in 1988. The encoder operates on 14-bit speech/audio signals sampled at 16 KHz and generates a compressed bit-stream having a bit rate of 64kbps. The codec transforms the speech/audio signals using the Sub-Band ADPCM (SB-ADPCM) algorithm. The application at the transmit side can truncate each octet generated by the encoder by 1 or 2 bits to insert auxiliary data before transmission. The codec therefore provides an auxiliary data channel rate of 0, 8 or 16 kbps respectively. Decoder can be operated in one of 3 modes corresponding to bitrates 64, 56 or 48 kbps respectively. Appendix IV of the standard specifies a low complexity PLC algorithm for the decoder. The target applications for this codec includes the fixed network Voice over IP applications.

Salient features

  • Based on ITU-T specification.
  • Optimized ASM/C implementation.
  • Re-entrant implementation.
  • C-callable APIs.
  • Operates on speech/audio signals sampled at 16 KHz.
  • Configurable frame length (minimum size -- 2 samples, default – 160 samples)
  • Support for 48, 56, and 64 kbps bit-rates.
  • Support for RTP payload format as specified in RFC 3551.
  • Support for packet loss concealment as specified in Appendix IV of the Standard.
  • Optional support for xDM APIs on TI platforms.

Testing features

  • Tested for bit-exactness with standard as well as a large database of non-standard test vectors.
  • Module is fully interruptible.
  • 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 with scratch contamination at frame boundaries.
  • Tested for packet loss conditions with 5% loss to 25% loss.
  • TI C64x implementation validated on Spectrum Digital C6416 DSK.
  • TI C64x+ implementation validated on Spectrum Digital C6455 DSK.
  • ARM implementation validated on OMAP3530 (Cortex-A8) and DM6446/DM6467 (ARM926EJ-S) platforms.

Available Platform(s)

ARM9E, ARM11, Cortex-A8, Cortex-A9, TI C55x, and TI C64x+.

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