micromod
Class Channel

java.lang.Object
  micromod.Channel

public class Channel

extends java.lang.Object

A Channel attemps to do a bit of Amiga hardware emulation to play ProTracker modules a bit better than most. In my experience, this implementation can play some modules that even SurfSmurf can't manage. There are still one or two tunes that won't sound entirely correct, but I believe this is one of the better implementations. The justification for the design of this class is that it provides a protracker specific channel interface and allows the InstrumentPlayer,LoopDecoder,resampler interfaces to be reused in other mod players. In fact, InstrumentPlayer and LoopDecoder have been hacked to better emulate ProTracker. This is an advantage of using different codebases for each module type.

Field Summary

protected int	amplitude
protected int	fineTune
protected int[]	fineTuneTable A log table for calculating fine tuned periods.
protected static int	FIXED_POINT_SHIFT
protected InstrumentPlayer	instrumentPlayer
protected int	leftPan
protected int	mixerStepPrecalc
protected int	period
protected int	rightPan
protected int	volume

Constructor Summary

Channel(int samplingRate, boolean pal)
Constructor

Method Summary

protected void	calculateMixerStep(int period, int fineTune) Calculate the step and subStep values for the resampler, from the specified period and fineTune value.
void	configure(int samplingRate, boolean pal) Configure the Channel to use the specified sampling rate and PAL/NTSC mode.
void	getAudio(short[] buffer, int length, Resampler resampler, boolean snapBack) Get resampled audio into the specified buffers.
int	getLeftAmplitude()
int	getPeriod() Get the current period of the channel.Used so the Modulator can, er, modulate
int	getRightAmplitude()
int	getVolume() Get the current ProTracker volume of the channel, from 0 to 64.
boolean	isSilent()
void	reset() Overrides reset() to reinitialise the default volume and period.
void	setFineTune(int fineTune) Set the finetune.
void	setPanning(int left, int right) Set the leftAmp and rightAmp members to specify the panning.
void	setPeriod(int period, boolean permanent) Set the period using the conventional ProTracker period notation.
void	setSamplePosition(int samplePosition) Set the current sample position
void	setVolume(int volume, boolean permanent) Set the volume from 0 to 64.
protected void	switchInstrument(boolean trig) Play the assigned instrument.
void	trigger(Instrument instrument, int period) Trigger an instrument on the channel to play at the specified pitch.

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

period

protected int period

volume

protected int volume

fineTune

protected int fineTune

amplitude

protected int amplitude

leftPan

protected int leftPan

rightPan

protected int rightPan

mixerStepPrecalc

protected int mixerStepPrecalc

instrumentPlayer

protected InstrumentPlayer instrumentPlayer

fineTuneTable

protected int[] fineTuneTable

A log table for calculating fine tuned periods.

Constructor Detail

Channel

public Channel(int samplingRate,
               boolean pal)

Constructor

Method Detail

configure

public void configure(int samplingRate,
                      boolean pal)

Configure the Channel to use the specified sampling rate and PAL/NTSC mode.

reset

public void reset()

Overrides reset() to reinitialise the default volume and period.

trigger

public void trigger(Instrument instrument,
                    int period)

Trigger an instrument on the channel to play at the specified pitch. Call this for every row, even if the row is empty, since it resets the volume and pitch modulations done by eg) vibrato/tremolo ProTracker behaviour is currently as follows: Valid instrument, period > 0 : Plays from instrument start as normal. Null instrument, period > 0 : Assigned instrument is triggered at period. Valid instrument, period = 0 : Instrument is "assigned" but not triggered. Valid instrument, period =-1 : Instrument is "switched over" without retrig. Anything else is ignored. This behaviour will probably change after some testing, since I know it's not exactly correct.

getPeriod

public int getPeriod()

Get the current period of the channel.Used so the Modulator can, er, modulate

getVolume

public int getVolume()

Get the current ProTracker volume of the channel, from 0 to 64.

setPeriod

public void setPeriod(int period,
                      boolean permanent)

Set the period using the conventional ProTracker period notation.

Parameters:

permanent - if false, the period change only affects one subsequent call to output()

setVolume

public void setVolume(int volume,
                      boolean permanent)

Set the volume from 0 to 64.

Parameters:

permanent - if false, the period change only affects one subsequent call to output()

setSamplePosition

public void setSamplePosition(int samplePosition)

Set the current sample position

setFineTune

public void setFineTune(int fineTune)

Set the finetune. The finetune of the channel is set automatically when an instrument is assigned. This method is used for the (useless) set finetune ProTracker command.

setPanning

public void setPanning(int left,
                       int right)

Set the leftAmp and rightAmp members to specify the panning. leftAmp and rightAmp are signed integers from -65536 to 65536 to specify the value a sample on either channel should be multiplied by. If one of these is negative, a "surround" effect can be achieved.

getLeftAmplitude

public int getLeftAmplitude()

Returns:

the current left-speaker amplitude of the channel, in 16 bit fixed point format. This value can be negative, and if it is, the audio should be inverted for a surround effect.

getRightAmplitude

public int getRightAmplitude()

Returns:

the current right-speaker amplitude of the channel, in 16 bit fixed point format. This value can be negative, and if it is, the audio should be inverted for a surround effect.

isSilent

public boolean isSilent()

Returns:

true if a call to getAudio() would result only in a blank buffer.

getAudio

public void getAudio(short[] buffer,
                     int length,
                     Resampler resampler,
                     boolean snapBack)

Get resampled audio into the specified buffers. Volume and panning are not applied. You must scale the amplitude according to getLeftAmplitude() and getRightAmplitude().

Parameters:

snapBack - Do not update the sample-pointers, so the same audio can be retrieved again.

switchInstrument

protected void switchInstrument(boolean trig)

Play the assigned instrument.

Parameters:

trig - If true, will play instrument from start.

calculateMixerStep

protected void calculateMixerStep(int period,
                                  int fineTune)

Calculate the step and subStep values for the resampler, from the specified period and fineTune value.