micromod.resamplers
Class FIRResampler

java.lang.Object
  micromod.resamplers.FIRResampler

All Implemented Interfaces:

Resampler

public class FIRResampler

extends java.lang.Object

implements Resampler

Table based multipoint FIR resampler. This took many, many hours to debug! Note to self: No more 12-hour sleep ins.

Field Summary

protected static int	FIXED_POINT_BITMASK
protected static int	FIXED_POINT_CONV
protected static int	FIXED_POINT_ONE
protected static int	FIXED_POINT_SHIFT
protected int	points
protected short[]	sinc

Constructor Summary

FIRResampler(int numPoints)
Constructor.

Method Summary

protected void	genSinc() Generate one wing of a Blackman windowed sinc equation.
int	getCushionSize() Return minimum number of samples required by the resampler before and after the audio to be processed.
void	resample(short[] inputBuf, int samplePos, int subSamplePos, int step, int subStep, short[] outputBuf, int position, int length) Do resampling.
protected static void	zero(short[] buffer, int start, int end)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

FIXED_POINT_SHIFT

protected static final int FIXED_POINT_SHIFT

See Also:

Constant Field Values

FIXED_POINT_ONE

protected static final int FIXED_POINT_ONE

See Also:

Constant Field Values

FIXED_POINT_BITMASK

protected static final int FIXED_POINT_BITMASK

See Also:

Constant Field Values

FIXED_POINT_CONV

protected static final int FIXED_POINT_CONV

See Also:

Constant Field Values

points

protected int points

sinc

protected short[] sinc

Constructor Detail

FIRResampler

public FIRResampler(int numPoints)

Constructor.

Parameters:

numPoints - The higher the better but more cpu and memory intensive. Even number, minimum 2.

Method Detail

resample

public void resample(short[] inputBuf,
                     int samplePos,
                     int subSamplePos,
                     int step,
                     int subStep,
                     short[] outputBuf,
                     int position,
                     int length)

Do resampling.

Specified by:

resample in interface Resampler

Parameters:

samplePos - The index of the sample in inputBuf

subSamplePos - The fractional part of the index, in 16 bit fixed point.

step - The integer part of the number of input samples per output sample.

subStep - The fractional part of the number of input samples per output sample. The value is in 16 bit fixed point.

position - The index of the output buffer to start writing to.

length - The number of samples of output to produce.

getCushionSize

public int getCushionSize()

Description copied from interface: Resampler

Return minimum number of samples required by the resampler before and after the audio to be processed. A cubic resampler might return 3, for example.

Specified by:

getCushionSize in interface Resampler

Returns:

the number of extra input samples required before and after the audio.

genSinc

protected void genSinc()

Generate one wing of a Blackman windowed sinc equation. According to Shannon's sampling theory, a sample should be rendered according to the equation A Sin(PI*t)/(PI*t) where the sampling frequency is 1/t. This equation goes to +-infinity so it is multiplied by a window function to make it tail off at the ends. The more points you use to render each sample, the more accurate the result. Linear interpolation is actually a very, very course approximation of the above "sinc" equation, which sorta explains why it works.

zero

protected static void zero(short[] buffer,
                           int start,
                           int end)