// license:BSD-3-Clause // copyright-holders:Andrew Gardner,Aaron Giles /*************************************************************************** okiadpcm.h OKI ADCPM emulation. ***************************************************************************/ #include "emu.h" #include "okiadpcm.h" //************************************************************************** // ADPCM STATE HELPER //************************************************************************** // ADPCM state and tables bool oki_adpcm_state::s_tables_computed = false; const int8_t oki_adpcm_state::s_index_shift[8] = { -1, -1, -1, -1, 2, 4, 6, 8 }; int oki_adpcm_state::s_diff_lookup[49*16]; //------------------------------------------------- // reset - reset the ADPCM state //------------------------------------------------- void oki_adpcm_state::reset() { // reset the signal/step m_signal = -2; m_step = 0; } //------------------------------------------------- // device_clock_changed - called if the clock // changes //------------------------------------------------- int16_t oki_adpcm_state::clock(uint8_t nibble) { // update the signal m_signal += s_diff_lookup[m_step * 16 + (nibble & 15)]; // clamp to the maximum if (m_signal > 2047) m_signal = 2047; else if (m_signal < -2048) m_signal = -2048; // adjust the step size and clamp m_step += s_index_shift[nibble & 7]; if (m_step > 48) m_step = 48; else if (m_step < 0) m_step = 0; // return the signal return m_signal; } //------------------------------------------------- // compute_tables - precompute tables for faster // sound generation //------------------------------------------------- void oki_adpcm_state::compute_tables() { // skip if we already did it if (s_tables_computed) return; s_tables_computed = true; // nibble to bit map static const int8_t nbl2bit[16][4] = { { 1, 0, 0, 0}, { 1, 0, 0, 1}, { 1, 0, 1, 0}, { 1, 0, 1, 1}, { 1, 1, 0, 0}, { 1, 1, 0, 1}, { 1, 1, 1, 0}, { 1, 1, 1, 1}, {-1, 0, 0, 0}, {-1, 0, 0, 1}, {-1, 0, 1, 0}, {-1, 0, 1, 1}, {-1, 1, 0, 0}, {-1, 1, 0, 1}, {-1, 1, 1, 0}, {-1, 1, 1, 1} }; // loop over all possible steps for (int step = 0; step <= 48; step++) { // compute the step value int stepval = floor(16.0 * pow(11.0 / 10.0, (double)step)); // loop over all nibbles and compute the difference for (int nib = 0; nib < 16; nib++) { s_diff_lookup[step*16 + nib] = nbl2bit[nib][0] * (stepval * nbl2bit[nib][1] + stepval/2 * nbl2bit[nib][2] + stepval/4 * nbl2bit[nib][3] + stepval/8); } } } //************************************************************************** // ADPCM2 STATE HELPER //************************************************************************** // ADPCM state and tables bool oki_adpcm2_state::s_tables_computed = false; const int8_t oki_adpcm2_state::s_index_shift[8] = { -2, -2, -2, -2, 2, 6, 9, 11 }; int oki_adpcm2_state::s_diff_lookup[49*16]; //------------------------------------------------- // reset - reset the ADPCM state //------------------------------------------------- void oki_adpcm2_state::reset() { // reset the signal/step m_signal = -2; m_step = 0; } //------------------------------------------------- // device_clock_changed - called if the clock // changes //------------------------------------------------- int16_t oki_adpcm2_state::clock(uint8_t nibble) { // update the signal m_signal += s_diff_lookup[m_step * 16 + (nibble & 15)]; // clamp to the maximum if (m_signal > 2047) m_signal = 2047; else if (m_signal < -2048) m_signal = -2048; // adjust the step size and clamp m_step += s_index_shift[nibble & 7]; if (m_step > 48) m_step = 48; else if (m_step < 0) m_step = 0; // return the signal return m_signal; } //------------------------------------------------- // compute_tables - precompute tables for faster // sound generation //------------------------------------------------- void oki_adpcm2_state::compute_tables() { // skip if we already did it if (s_tables_computed) return; s_tables_computed = true; // nibble to bit map static const int8_t nbl2bit[16][4] = { { 1, 0, 0, 0}, { 1, 0, 0, 1}, { 1, 0, 1, 0}, { 1, 0, 1, 1}, { 1, 1, 0, 0}, { 1, 1, 0, 1}, { 1, 1, 1, 0}, { 1, 1, 1, 1}, {-1, 0, 0, 0}, {-1, 0, 0, 1}, {-1, 0, 1, 0}, {-1, 0, 1, 1}, {-1, 1, 0, 0}, {-1, 1, 0, 1}, {-1, 1, 1, 0}, {-1, 1, 1, 1} }; // loop over all possible steps float floatstep = 64; for (int step = 0; step <= 48; step++) { // compute the step value int stepval = floor(floatstep * 1.08f); floatstep = floatstep * 1.08f; // loop over all nibbles and compute the difference for (int nib = 0; nib < 16; nib++) { s_diff_lookup[step*16 + nib] = nbl2bit[nib][0] * (stepval * nbl2bit[nib][1] + stepval/2 * nbl2bit[nib][2] + stepval/4 * nbl2bit[nib][3] + stepval/8); } } }