feat(snd): implement channel 3
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d145ae44f3
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48
src/sound.rs
48
src/sound.rs
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@ -8,7 +8,6 @@ use crate::Cycle;
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const WAVE_PATTERN_RAM_LEN: usize = 0x10;
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const SAMPLE_RATE: u32 = 48000; // Hz
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const SAMPLE_INCREMENT: u64 = SAMPLE_RATE as u64;
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const SAMPLE_RATE_IN_CYCLES: Cycle = Cycle::new((SM83_CLOCK_SPEED / SAMPLE_RATE as u64) as u32);
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#[derive(Debug, Clone, Default)]
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pub(crate) struct Sound {
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@ -62,13 +61,14 @@ impl Sound {
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self.ch1.clock();
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self.ch2.clock();
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self.ch3.clock();
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self.ch4.clock();
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self.div_prev = Some(bit_5);
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if self.sample_counter >= SM83_CLOCK_SPEED {
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// Sample the APU
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self.sample_counter %= SM83_CLOCK_SPEED;
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// Sample the APU
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let ch1_amplitude = self.ch1.amplitude();
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let ch1_left = self.ctrl.output.ch1_left() as u8 as f32 * ch1_amplitude;
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@ -78,12 +78,16 @@ impl Sound {
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let ch2_left = self.ctrl.output.ch2_left() as u8 as f32 * ch2_amplitude;
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let ch2_right = self.ctrl.output.ch2_right() as u8 as f32 * ch2_amplitude;
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let ch3_amplitude = self.ch3.amplitude();
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let ch3_left = self.ctrl.output.ch3_left() as u8 as f32 * ch3_amplitude;
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let ch3_right = self.ctrl.output.ch3_right() as u8 as f32 * ch3_amplitude;
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let ch4_amplitude = self.ch4.amplitude();
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let ch4_left = self.ctrl.output.ch4_left() as u8 as f32 * ch4_amplitude;
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let ch4_right = self.ctrl.output.ch4_right() as u8 as f32 * ch4_amplitude;
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let left_sample = (ch1_left + ch2_left + ch4_left) / 3.0;
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let right_sample = (ch1_right + ch2_right + ch4_right) / 3.0;
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let left_sample = (ch1_left + ch2_left + ch3_left + ch4_left) / 4.0;
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let right_sample = (ch1_right + ch2_right + ch3_right + ch4_right) / 4.0;
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if let Some(send) = self.sender.as_ref() {
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send.add_sample(left_sample, right_sample);
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@ -776,6 +780,9 @@ pub(crate) struct Channel3 {
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// Length Functionality
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length_timer: u16,
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freq_timer: u16,
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offset: u8,
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}
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impl Channel3 {
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@ -835,6 +842,39 @@ impl Channel3 {
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_ => unreachable!("{:#04X} is not a valid value for Channel3Volume", byte),
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};
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}
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fn amplitude(&self) -> f32 {
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let dac_input = self.read_sample(self.offset) >> self.volume.shift_count();
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(dac_input as f32 / 7.5) - 1.0
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}
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fn clock(&mut self) {
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if self.freq_timer != 0 {
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self.freq_timer -= 1;
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}
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if self.freq_timer == 0 {
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self.freq_timer = (2048 - self.frequency()) * 4;
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self.offset = (self.offset + 1) % 8;
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}
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}
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fn read_sample(&self, index: u8) -> u8 {
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let i = index as usize / 2;
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if index % 2 == 0 {
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// We grab the high nibble on even indexes
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self.wave_ram[i] >> 4
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} else {
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// We grab the low nibble on odd indexes
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self.wave_ram[i] & 0x0F
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}
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}
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fn frequency(&self) -> u16 {
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(self.freq_hi.freq_bits() as u16) << 8 | self.freq_lo as u16
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}
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}
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#[derive(Debug, Clone, Copy)]
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