Sample Rate Converter



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Sample Rate Converter :: Overview

Sample Rate Converter (SRC) is used for converting a digitized speech/audio stream sampled at a specific frequency to a desired sampling frequency. The algorithm interpolates the new samples using a truncated sinc function (low pass) filter. The performance of the algorithm is dependent on the length of the filter and there is a trade-off between quality (SNR, bandwidth) and complexity (memory and MCPS). SRC is used in digital audio mixing consoles, multimedia players, and for converting the sampling frequencies for interoperability issues.

Salient features

  • ANSI-C fixed-point implementation.
  • Re-entrant implementation
  • Support for low complexity (memory footprint and MCPS) with different filter lengths at compile time.
  • Supported filter lengths are 32, 48, 84 and 276.
  • Supports input sampling frequencies from 8KHz to 48KHz (8, 11.025, 12, 16, 22.05, 24, 32, 44.1, 48).
  • Supports output sampling frequencies from 8KHz to 48KHz (8, 11.025, 12, 16, 22.05, 24, 32, 44.1, 48).
  • With filter length of 276, SNR > 100 dB when the re-sampling factor is a multiple of 2; ~90 dB for other cases.
  • Supports mono and stereo input and output.
  • Supports interleaved stereo at input and output.
  • Accepts 16-bit PCM at input.
  • Generates 16-bit PCM output.
  • Code validated on TI C64x+ platform.

Testing features

  • Tested using a large database of speech and audio samples.
  • Exhaustively tested for overflow conditions with high energy test cases.
  • Objectively benchmarked with SNR, Bandwidth and Stopband rejection tests.
  • Subjective listening tests to ensure that there are no audible errors.
  • Verified linearity of the phase response of the filters.

Available Platform(s)

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

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