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saa1099.cpp: Fix output behavior when both noise and tone are enabled (#8767)

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cam900 2021-10-29 22:42:33 +09:00 committed by GitHub
parent fcd99ff769
commit 4a7cbbb858
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1 changed files with 24 additions and 9 deletions
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33
src/devices/sound/saa1099.cpp
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@ -249,23 +249,38 @@ void saa1099_device::sound_stream_update(sound_stream &stream, std::vector<read_
}
m_channels[ch].counter -= clock_divider;
u8 level = 0; // output level (0...2, 0 = off, 1 = 100%, 2 = 50%)
// if the noise is enabled
u8 level = 0;
u8 noise_out = m_noise[ch/3].level & 1; // noise output (noise 0: chan 0-2, noise 1: chan 3-5)
u8 tone_out = m_channels[ch].level & 1; // tone output
if (m_channels[ch].noise_enable)
{
// if the noise level is high (noise 0: chan 0-2, noise 1: chan 3-5)
level ^= m_noise[ch/3].level & 1;
// if both noise and square wave are enabled, output is tone output
if (m_channels[ch].freq_enable)
{
// half amplitude if the noise level is high
if (noise_out)
level = tone_out << 1;
else
level = tone_out;
}
else
{
// output is noise output
level = noise_out;
}
}
// if the square wave is enabled
if (m_channels[ch].freq_enable)
else if (m_channels[ch].freq_enable)
{
// if the channel level is high
level ^= m_channels[ch].level & 1;
// output is tone output
level = tone_out;
}
if (level)
// if the output level is high
if (level > 0)
{
output_l += m_channels[ch].amplitude[ LEFT] * m_channels[ch].envelope[ LEFT] / 16;
output_r += m_channels[ch].amplitude[RIGHT] * m_channels[ch].envelope[RIGHT] / 16;
output_l += m_channels[ch].amplitude[ LEFT] * m_channels[ch].envelope[ LEFT] / 16 / level;
output_r += m_channels[ch].amplitude[RIGHT] * m_channels[ch].envelope[RIGHT] / 16 / level;
}
}