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//-----------------------------------------------------------------------------
// Name: transition_mixer.cpp
// Developer: Wolfire Games LLC
// Description:
// License: Read below
//-----------------------------------------------------------------------------
//
// Copyright 2022 Wolfire Games LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
//-----------------------------------------------------------------------------
#include "transition_mixer.h"
#include <Logging/logdata.h>
#include <Utility/assert.h>
#include <cmath>
#include <algorithm>
#define PI 3.141592653589793238462643383279502884197169399375105820974944592308
TransitionMixer::TransitionMixer( TransitionType trans_type, float transition_length_seconds ) :
transition_type( trans_type ),
transition_length_sec( transition_length_seconds ),
transition_position(0)
{
}
bool TransitionMixer::Step( HighResBufferSegment* out, const HighResBufferSegment* first, const HighResBufferSegment* second )
{
LOG_ASSERT( first->sample_rate == second->sample_rate );
LOG_ASSERT( first->channels == second->channels );
out->sample_rate = first->sample_rate;
out->channels = first->channels;
out->data_size = out->SampleSize() * std::max(first->FlatSampleCount(),second->FlatSampleCount());
size_t start = transition_position;
//How many bytes for a second of transition times the time of transition.
size_t end = (size_t) (transition_length_sec * first->sample_rate * first->channels);
size_t i = 0;
//This casting union is possible because we take endianess into account when we get the first from the underlying loader.
//If we use architecture inspecific endianess we have to bitshift this data instead.
//Also note that use of a union for aliasing is not strictly allowed until C99, but generally implemented and faster than shifting.
union casterunion
{
int32_t full;
char part[4];
};
casterunion out1;
casterunion buf1;
casterunion buf2;
//Crossfade the two firsts together.
for( i = 0; i < out->FlatSampleCount(); i++ )
{
float d = (float)(start+i)/(float)(end);
if( d > 1.0f ) {
d = 1.0f;
}
float dl;
float dr;
if( transition_type == Sinusoid )
{
//Crossfade in a sinusoid to preserve the energy.
float dp = d*(float)PI/2;
dl = sin(dp);
dr = cos(dp);
}
else if( transition_type == Linear )
{
dl = d;
dr = 1.0f-d;
}
else
{
LOGE << "No transition function used" << std::endl;
dl = 1.0f;
dr = 0.0f;
}
if( i < first->FlatSampleCount() ) {
buf1.part[0] = first->buf[i*4+0];
buf1.part[1] = first->buf[i*4+1];
buf1.part[2] = first->buf[i*4+2];
buf1.part[3] = first->buf[i*4+3];
} else {
buf1.full = 0;
}
if( i < second->FlatSampleCount() ) {
buf2.part[0] = second->buf[i*4+0];
buf2.part[1] = second->buf[i*4+1];
buf2.part[2] = second->buf[i*4+2];
buf2.part[3] = second->buf[i*4+3];
} else {
buf2.full = 0;
}
out1.full = (int32_t) (buf1.full*dr+buf2.full*dl);
out->buf[i*4+0] = out1.part[0];
out->buf[i*4+1] = out1.part[1];
out->buf[i*4+2] = out1.part[2];
out->buf[i*4+3] = out1.part[3];
}
//If it happened that the second first had more data than the first, indicate that
// we continued writing into the main first so we don't miss that segment of audio
// that was streamed.
transition_position += i;
if( transition_position >= end )
{
transition_position = end;
return true;
}
return false;
}
void TransitionMixer::Reset()
{
transition_position = 0;
}
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