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Add some comments to linear scaler and renamed floor and ceil samples
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@daschuer
daschuer committed Mar 28, 2015
1 parent db17306 commit 00d47e5
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Showing 2 changed files with 44 additions and 38 deletions.
80 changes: 43 additions & 37 deletions src/engine/enginebufferscalelinear.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ EngineBufferScaleLinear::EngineBufferScaleLinear(ReadAheadManager *pReadAheadMan
m_dNextFrame(0.0)
{
for (int i=0; i<2; i++)
m_fPrevSample[i] = 0.0f;
m_floorSampleOld[i] = 0.0f;

m_bufferInt = new CSAMPLE[kiLinearScaleReadAheadLength];
m_bufferIntSize = 0;
Expand Down Expand Up @@ -69,8 +69,8 @@ void EngineBufferScaleLinear::clear() {
// Clear out buffer and saved sample data
m_bufferIntSize = 0;
m_dNextFrame = 0;
m_fPrevSample[0] = 0;
m_fPrevSample[1] = 0;
m_floorSampleOld[0] = 0;
m_floorSampleOld[1] = 0;
}

// laurent de soras - punked from musicdsp.org (mad props)
Expand Down Expand Up @@ -114,8 +114,8 @@ CSAMPLE* EngineBufferScaleLinear::getScaled(unsigned long buf_size) {
int iCurSample = static_cast<int>(ceil(m_dCurrentFrame)) * 2;
if (iCurSample + 1 < m_bufferIntSize) {
int iNextSample = static_cast<int>(ceil(m_dNextFrame)) * 2;
m_fPrevSample[0] = m_bufferInt[iNextSample];
m_fPrevSample[1] = m_bufferInt[iNextSample + 1];
m_floorSampleOld[0] = m_bufferInt[iNextSample];
m_floorSampleOld[1] = m_bufferInt[iNextSample + 1];
}

// if the buffer has extra samples, do a read so RAMAN ends up back where
Expand All @@ -127,7 +127,7 @@ CSAMPLE* EngineBufferScaleLinear::getScaled(unsigned long buf_size) {
//qDebug() << "extra samples" << extra_samples;

samples_read += m_pReadAheadManager->getNextSamples(
rate_add_new, m_bufferInt, extra_samples);
rate_add_new, m_bufferInt, extra_samples);
}
//force a buffer read:
m_bufferIntSize=0;
Expand Down Expand Up @@ -231,8 +231,8 @@ CSAMPLE* EngineBufferScaleLinear::do_scale(CSAMPLE* buf,
// blow away the fractional sample position here
m_bufferIntSize = 0; // force buffer read
m_dNextFrame = 0;
m_fPrevSample[0] = buf[read_samples-2];
m_fPrevSample[1] = buf[read_samples-1];
m_floorSampleOld[0] = buf[read_samples-2];
m_floorSampleOld[1] = buf[read_samples-1];
return buf;
}

Expand Down Expand Up @@ -260,13 +260,13 @@ CSAMPLE* EngineBufferScaleLinear::do_scale(CSAMPLE* buf,
double unscaled_samples_needed = math_max<long>(2, unscaled_frames_needed * 2);

bool last_read_failed = false;
CSAMPLE prev_sample[2];
CSAMPLE cur_sample[2];
CSAMPLE floor_sample[2];
CSAMPLE ceil_sample[2];

prev_sample[0] = 0;
prev_sample[1] = 0;
cur_sample[0] = 0;
cur_sample[1] = 0;
floor_sample[0] = 0;
floor_sample[1] = 0;
ceil_sample[0] = 0;
ceil_sample[1] = 0;

int i = 0;
int screwups = 0;
Expand All @@ -283,13 +283,17 @@ CSAMPLE* EngineBufferScaleLinear::do_scale(CSAMPLE* buf,

if (static_cast<int>(floor(m_dCurrentFrame)) * 2 + 1 < m_bufferIntSize
&& m_dCurrentFrame >= 0.0) {
prev_sample[0] = m_bufferInt[static_cast<int>(
// take floor_sample form the buffer of the previous run
floor_sample[0] = m_bufferInt[static_cast<int>(
floor(m_dCurrentFrame)) * 2];
prev_sample[1] = m_bufferInt[static_cast<int>(
floor_sample[1] = m_bufferInt[static_cast<int>(
floor(m_dCurrentFrame)) * 2 + 1];
} else {
prev_sample[0] = m_fPrevSample[0];
prev_sample[1] = m_fPrevSample[1];
// we have advanced to a new buffer in the previous run,
// bud the floor still points to the old buffer
// so take the cached sample, happens on slow rates
floor_sample[0] = m_floorSampleOld[0];
floor_sample[1] = m_floorSampleOld[1];
}

// Smooth any changes in the playback rate over iRateLerpLength
Expand All @@ -298,7 +302,7 @@ CSAMPLE* EngineBufferScaleLinear::do_scale(CSAMPLE* buf,
float rate_add = static_cast<float>(i) * (rate_add_diff) /
static_cast<float>(iRateLerpLength) + rate_add_old;

// if we don't have enough samples, load some more
// if we don't have the ceil_sample in buffer, load some more
while (static_cast<int>(ceil(m_dCurrentFrame)) * 2 + 1 >=
m_bufferIntSize) {
int old_bufsize = m_bufferIntSize;
Expand All @@ -321,42 +325,44 @@ CSAMPLE* EngineBufferScaleLinear::do_scale(CSAMPLE* buf,
last_read_failed = m_bufferIntSize == 0;

unscaled_samples_needed -= m_bufferIntSize;
// shift the index by the size of the old buffer

// adapt the m_dCurrentFrame the index of the new buffer
m_dCurrentFrame -= old_bufsize / 2.;
}

// I guess?
if (last_read_failed) {
break;
}

// Now that the buffer is up to date, we can get the value of the sample
// at the floor of our position.
if (static_cast<int>(floor(m_dCurrentFrame)) * 2 >= 0.0) {
prev_sample[0] = m_bufferInt[static_cast<int>(
// the previous position is in the new buffer
floor_sample[0] = m_bufferInt[static_cast<int>(
floor(m_dCurrentFrame)) * 2];
prev_sample[1] = m_bufferInt[static_cast<int>(
floor_sample[1] = m_bufferInt[static_cast<int>(
floor(m_dCurrentFrame)) * 2 + 1];
}

// I guess?
if (last_read_failed) {
break;
}

cur_sample[0] = m_bufferInt[static_cast<int>(
ceil_sample[0] = m_bufferInt[static_cast<int>(
ceil(m_dCurrentFrame)) * 2];
cur_sample[1] = m_bufferInt[static_cast<int>(
ceil_sample[1] = m_bufferInt[static_cast<int>(
ceil(m_dCurrentFrame)) * 2 + 1];

// For the current index, what percentage is it
// between the previous and the next?
CSAMPLE frac = m_dCurrentFrame - floor(m_dCurrentFrame);

// Perform linear interpolation
buf[i] = static_cast<float>(prev_sample[0]) +
frac * (static_cast<float>(cur_sample[0]) -
static_cast<float>(prev_sample[0]));
buf[i+1] = static_cast<float>(prev_sample[1]) +
frac * (static_cast<float>(cur_sample[1]) -
static_cast<float>(prev_sample[1]));
m_fPrevSample[0] = prev_sample[0];
m_fPrevSample[1] = prev_sample[1];
buf[i] = static_cast<float>(floor_sample[0]) +
frac * (static_cast<float>(ceil_sample[0]) -
static_cast<float>(floor_sample[0]));
buf[i + 1] = static_cast<float>(floor_sample[1]) +
frac * (static_cast<float>(ceil_sample[1]) -
static_cast<float>(floor_sample[1]));
m_floorSampleOld[0] = floor_sample[0];
m_floorSampleOld[1] = floor_sample[1];

// increment the index for the next loop
m_dNextFrame = m_dCurrentFrame +
Expand Down
2 changes: 1 addition & 1 deletion src/engine/enginebufferscalelinear.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -55,7 +55,7 @@ class EngineBufferScaleLinear : public EngineBufferScale {
// Buffer for handling calls to ReadAheadManager
CSAMPLE* m_bufferInt;
int m_bufferIntSize;
CSAMPLE m_fPrevSample[2];
CSAMPLE m_floorSampleOld[2];
// The read-ahead manager that we use to fetch samples
ReadAheadManager* m_pReadAheadManager;
double m_dCurrentFrame;
Expand Down

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