QCELP13k

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QCELP13k (Decoder)

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Codec overview

QCELP13k is a variable rate speech codec standardized by TIA in 1997 and a revised description of this codec is given in TIA-733-A. QCELP13k operates on 14-bit speech signal sampled at 8 Khz and generates compressed bit-stream with four different rates namely full-rate (13.3kbps), half-rate (6.2kbps), quater-rate (2.7kbps) and eighth-rate (1kbps). It operates on frames of 20ms duration. Encoder selects appropriate rate depending on the speech activity: in full-rate mode 20ms frame encodes to 266 bits, in half-rate mode it encodes to 124 bits, in quarter-rate mode it encodes to 54 bits, and in eighth-rate mode it encodes to 20 bits. The speech coding algorithm is based on Code Excited Linear Prediction(CELP). QCELP13K is used in service option 17, a two-way voice communications between the base station and mobile station.

Salient features

  • Based on TIA/EIA/IS-733 floating point specification.
  • Optimized C implementation (decoder).
  • Re-entrant implementation
  • C-callable APIs.
  • Support for 13.3 kbps, 6.2 kbps, 2.7kbps and 1 kbps bitrates.
  • Support for TTY/TDD signals as specified in the standard.
  • Supports integrated Packet Loss Concealment (PLC) algorithm.
  • Support for post-filter operation, configurable at frame boundary.
  • Supports decoding of QCP streams as per RFC3625.
  • Optional support for decoding of 3g2 streams.
  • Optional support for xDM APIs.
  • Support for Little Endian implementation on ARM.

Testing features

  • Fixed-point implementation is tested objectively for PESQ, Log likelihood ratio, weighted spectral slope and segmental SNR.
  • Module is fully interruptible.
  • ARM implementation tested for any illegal memory access.
  • 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.
  • Tested with scratch contamination at frame boundary.
  • 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.

Available Platform(s)

ARM9E, ARM11, Cortex-A8, and Cortex-A9

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