// license:BSD-3-Clause
// copyright-holders:Andrew Gardner,Aaron Giles
/***************************************************************************
okiadpcm.h
OKI ADPCM emulation.
See the following patents/applications:
(Note: if not registered, the application below was not actually granted, and is effectively abandoned)
Application JP,1980-109800 (Unexamined Publication JP,S57-035434,A) (Examined Publication JP,S61-024850,B) (Registration number JP,1356613,B) https://patents.google.com/patent/JPS5735434A/en
Application JP,1981-185490 (Unexamined Publication JP,S58-088926,A) (Not examined or registered) https://patents.google.com/patent/JPS5888926A/en
Application JP,1982-213971 (Unexamined Publication JP,S59-104699,A) (Not examined or registered) https://patents.google.com/patent/JPS59104699A/en <- this one goes into a bit more detail/better arranged diagrams, and shows a Q table with entries 0-63 rather than 0-48 of the real msm5205
Application JP,1987-184421 (Unexamined Publication JP,S64-028700,A) (Not examined) (Registration number JP,2581696,B) https://patents.google.com/patent/JPS6428700A/en <- quad band coding system for adpcm?
Application JP,1994-039523 (Unexamined Publication JP,H07-248798,A) (Not examined) (Registration number JP,3398457,B) https://patents.google.com/patent/JP3398457B2/en <- this may cover the 'adpcm2' method
Application JP,1995-104333 (Unexamined Publication JP,H08-307371,A) (Not examined or registered) https://patents.google.com/patent/JPH08307371A/en <- something unrelated to adpcm, wireless transmission error detection related?
Application JP,1995-162009 (Unexamined Publication JP,H09-018425,A) (Not examined or registered) https://patents.google.com/patent/JPH0918425A/en <- looks like ADPCM2 maybe?
Application JP,1988-176215 (Unexamined Publication JP,H02-026426,A) (Not examined or registered) https://patents.google.com/patent/JPH0226426A/en <- Fujitsu variant on (G.726/727?) SB-ADPCM, cited by above
***************************************************************************/
#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);
}
}
}