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Audio Output: Implement more upmixing modes, and correct some upmixing behavior

CQTexperiment
Christopher Snowhill 2021-12-28 00:09:57 -08:00
parent ad3058c4f3
commit 258a56a276
1 changed files with 22 additions and 3 deletions
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25
Audio/Chain/ConverterNode.m
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@ -125,20 +125,39 @@ static void upmix(float * buffer, int inchannels, int outchannels, int count)
{
for (int i = count - 1; i >= 0; --i)
{
if (inchannels == 1)
if (inchannels == 1 && outchannels == 2)
{
// upmix mono to stereo
float sample = buffer[i];
buffer[i * 2 + 0] = sample;
buffer[i * 2 + 1] = sample;
}
else if (inchannels == 1 && outchannels == 4)
{
// upmix mono to quad
float sample = buffer[i];
buffer[i * 4 + 0] = sample;
buffer[i * 4 + 1] = sample;
buffer[i * 4 + 2] = 0;
buffer[i * 4 + 3] = 0;
}
else if (inchannels == 1 && (outchannels == 3 || outchannels >= 5))
{
// upmix mono to center channel
float sample = buffer[i];
buffer[i * outchannels + 2] = sample;
for (int j = 0; j < 2; ++j)
{
buffer[i * outchannels + j] = sample;
buffer[i * outchannels + j] = 0;
}
for (int j = 2; j < outchannels; ++j)
for (int j = 3; j < outchannels; ++j)
{
buffer[i * outchannels + j] = 0;
}
}
else
{
// upmix N channels to N channels plus silence the empty channels
float samples[inchannels];
for (int j = 0; j < inchannels; ++j)
{