- Increase dynamic range of filter coefficients from 28bit to 30bit.

  This cause dramatic effect in overall precision and conversion quality
  by pushing down most aliasing artifacts around -180 dB.

  Spectrogram analysis/comparison:

  	http://people.freebsd.org/~ariff/z_comparison/z_28vs30/

- Guard against possible 64bit overflow during accumulation process by
  slightly normalize and saturate sample and coefficient multiplication,
  possible during extreme 32bit downsampling (eg. 380KHz -> 8KHz) with
  custom preset that require more than ~7000 taps filter (which is
  overkill).

- Add knobs through FEEDER_RATE_PRESETS to set dynamic range of filter
  coefficients/accumulator and prefered polynomial interpolator:

  	COEFFICIENT_BIT:X
	(where 1 <= X <= 30, default: 30)

	ACCUMULATOR_BIT:X
	(where 32 <= X <=64, default: 58)

	INTERPOLATOR:I
	(where I = ZOH, LINEAR, QUADRATIC, HERMITE, BSPLINE,
 	           OPT32X, OPT16X, OPT8X, OPT4X, OPT2X)

Approved by:	re (kib)

0 files changed, 0 insertions, 0 deletions