/// <summary>
/// Transposes down the sample rate, causing the observed playback
/// 'rate' of the sound to increase
/// </summary>
private void Downsample(ArrayPtr <TSampleType> src, int numSamples)
{
// If the parameter 'uRate' value is larger than 'SCALE', first apply the
// anti-alias filter to remove high frequencies (prevent them from folding
// over the lover frequencies), then transpose.
// Add the new samples to the end of the storeBuffer
_storeBuffer.PutSamples(src, numSamples);
// Anti-alias filter the samples to prevent folding and output the filtered
// data to tempBuffer. Note : because of the FIR filter length, the
// filtering routine takes in 'filter_length' more samples than it outputs.
Debug.Assert(_tempBuffer.IsEmpty);
var sizeTemp = _storeBuffer.AvailableSamples;
int count = _antiAliasFilter.Evaluate(_tempBuffer.PtrEnd(sizeTemp), _storeBuffer.PtrBegin(), sizeTemp, _channels);
if (count == 0)
{
return;
}
// Remove the filtered samples from 'storeBuffer'
_storeBuffer.ReceiveSamples(count);
// Transpose the samples (+16 is to reserve some slack in the destination buffer)
sizeTemp = (int)(numSamples / Rate + 16.0f);
count = Transpose(_outputBuffer.PtrEnd(sizeTemp), _tempBuffer.PtrBegin(), count);
_outputBuffer.PutSamples(count);
}
public virtual int Transpose(FifoSampleBuffer <TSampleType> dest, FifoSampleBuffer <TSampleType> src)
{
int numSrcSamples = src.AvailableSamples;
int sizeDemand = (int)(numSrcSamples / rate) + 8;
int numOutput;
ArrayPtr <TSampleType> psrc = src.PtrBegin();
ArrayPtr <TSampleType> pdest = dest.PtrEnd(sizeDemand);
#if !USE_MULTICH_ALWAYS
if (channels == 1)
{
numOutput = TransposeMono(pdest, psrc, ref numSrcSamples);
}
else if (channels == 2)
{
numOutput = TransposeStereo(pdest, psrc, ref numSrcSamples);
}
else
#endif
{
Debug.Assert(channels > 0);
numOutput = TransposeMulti(pdest, psrc, ref numSrcSamples);
}
dest.PutSamples(numOutput);
src.ReceiveSamples(numSrcSamples);
return(numOutput);
}
/// <summary>
/// Processes as many processing frames of the samples <see cref="_inputBuffer"/>, store
/// the result into <see cref="_outputBuffer"/>
/// </summary>
private void ProcessSamples()
{
// Process samples as long as there are enough samples in '_inputBuffer'
// to form a processing frame.
while (_inputBuffer.AvailableSamples >= _sampleReq)
{
// If tempo differs from the normal ('SCALE'), scan for the best overlapping
// position
int offset = SeekBestOverlapPosition(_inputBuffer.PtrBegin());
// Mix the samples in the '_inputBuffer' at position of 'offset' with the
// samples in 'midBuffer' using sliding overlapping
// ... first partially overlap with the end of the previous sequence
// (that's in 'midBuffer')
Overlap(_outputBuffer.PtrEnd(_overlapLength), _inputBuffer.PtrBegin(), offset);
_outputBuffer.PutSamples(_overlapLength);
// ... then copy sequence samples from '_inputBuffer' to output:
// length of sequence
int temp = (_seekWindowLength - 2 * _overlapLength);
// crosscheck that we don't have buffer overflow...
if (_inputBuffer.AvailableSamples < (offset + temp + _overlapLength * 2))
{
continue; // just in case, shouldn't really happen
}
_outputBuffer.PutSamples(_inputBuffer.PtrBegin() + _channels * (offset + _overlapLength), temp);
// Copies the end of the current sequence from '_inputBuffer' to
// 'midBuffer' for being mixed with the beginning of the next
// processing sequence and so on
Debug.Assert((offset + temp + _overlapLength * 2) <= _inputBuffer.AvailableSamples);
ArrayPtr <TSampleType> .CopyBytes(_midBuffer, _inputBuffer.PtrBegin() + _channels *(offset + temp + _overlapLength),
_channels *SIZEOF_SAMPLETYPE *_overlapLength);
// Remove the processed samples from the input buffer. Update
// the difference between integer & nominal skip step to '_skipFract'
// in order to prevent the error from accumulating over time.
_skipFract += _nominalSkip; // real skip size
var ovlSkip = (int)_skipFract;
_skipFract -= ovlSkip; // maintain the fraction part, i.e. real vs. integer skip
_inputBuffer.ReceiveSamples(ovlSkip);
}
}
public int Evaluate(FifoSampleBuffer <TSampleType> dest, FifoSampleBuffer <TSampleType> src)
{
ArrayPtr <TSampleType> pdest;
ArrayPtr <TSampleType> psrc;
int numSrcSamples;
int result;
int numChannels = src.GetChannels();
Debug.Assert(numChannels == dest.GetChannels());
numSrcSamples = src.AvailableSamples;
psrc = src.PtrBegin();
pdest = dest.PtrEnd(numSrcSamples);
result = _firFilter.Evaluate(pdest, psrc, numSrcSamples, numChannels);
src.ReceiveSamples(result);
dest.PutSamples(result);
return(result);
}