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#include "includes/channelf.h"
static const int max_amplitude = 0x7fff;
typedef struct _channelf_sound_state channelf_sound_state;
struct _channelf_sound_state
{
sound_stream *channel;
int sound_mode;
int incr;
float decay_mult;
int envelope;
UINT32 sample_counter;
int forced_ontime; // added for improved sound
int min_ontime; // added for improved sound
};
INLINE channelf_sound_state *get_safe_token(device_t *device)
{
assert(device != NULL);
assert(device->type() == CHANNELF);
return (channelf_sound_state *)downcast<channelf_sound_device *>(device)->token();
}
void channelf_sound_w(device_t *device, int mode)
{
channelf_sound_state *state = get_safe_token(device);
if (mode == state->sound_mode)
return;
state->channel->update();
state->sound_mode = mode;
switch(mode)
{
case 0:
state->envelope = 0;
state->forced_ontime = 0; // added for improved sound
break;
case 1:
case 2:
case 3:
state->envelope = max_amplitude;
state->forced_ontime = state->min_ontime; // added for improved sound
break;
}
}
static STREAM_UPDATE( channelf_sh_update )
{
channelf_sound_state *state = get_safe_token(device);
UINT32 mask = 0, target = 0;
stream_sample_t *buffer = outputs[0];
stream_sample_t *sample = buffer;
switch( state->sound_mode )
{
case 0: /* sound off */
memset(buffer,0,sizeof(*buffer)*samples);
return;
case 1: /* high tone (2V) - 1000Hz */
mask = 0x00010000;
target = 0x00010000;
break;
case 2: /* medium tone (4V) - 500Hz */
mask = 0x00020000;
target = 0x00020000;
break;
case 3: /* low (weird) tone (32V & 8V) */
mask = 0x00140000;
target = 0x00140000;
break;
}
while (samples-- > 0)
{
if ((state->forced_ontime > 0) || ((state->sample_counter & mask) == target)) // change made for improved sound
*sample++ = state->envelope;
else
*sample++ = 0;
state->sample_counter += state->incr;
state->envelope *= state->decay_mult;
if (state->forced_ontime > 0) // added for improved sound
state->forced_ontime -= 1; // added for improved sound
}
}
static DEVICE_START(channelf_sound)
{
channelf_sound_state *state = get_safe_token(device);
int rate;
state->channel = device->machine().sound().stream_alloc(*device, 0, 1, device->machine().sample_rate(), 0, channelf_sh_update);
rate = device->machine().sample_rate();
/*
* 2V = 1000Hz ~= 3579535/224/16
* Note 2V on the schematic is not the 2V scanline counter -
* it is the 2V vertical pixel counter
* 1 pixel = 4 scanlines high
*
*
* This is a convenient way to generate the relevant frequencies,
* using a DDS (Direct Digital Synthesizer)
*
* Essentially, you want a counter to overflow some bit position
* at a fixed rate. So, you figure out a number which you can add
* to the counter at every sample, so that you will achieve this
*
* In this case, we want to overflow bit 16 and the 2V rate, 1000Hz.
* This means we also get bit 17 = 4V, bit 18 = 8V, etc.
*/
/* This is the proper value to add per sample */
state->incr = 65536.0/(rate/1000.0/2.0);
// added for improved sound
/* This is the minimum forced ontime, in samples */
state->min_ontime = rate/1000*2; /* approx 2ms - estimated, not verified on HW */
/* This was measured, decay envelope with half life of ~9ms */
/* (this is decay multiplier per sample) */
state->decay_mult = exp((-0.693/9e-3)/rate);
/* initial conditions */
state->envelope = 0;
}
DEVICE_GET_INFO( channelf_sound )
{
switch (state)
{
/* --- the following bits of info are returned as 64-bit signed integers --- */
case DEVINFO_INT_TOKEN_BYTES: info->i = sizeof(channelf_sound_state); break;
/* --- the following bits of info are returned as pointers to data or functions --- */
case DEVINFO_FCT_START: info->start = DEVICE_START_NAME(channelf_sound); break;
/* --- the following bits of info are returned as NULL-terminated strings --- */
case DEVINFO_STR_NAME: strcpy(info->s, "Channel F"); break;
case DEVINFO_STR_SOURCE_FILE: strcpy(info->s, __FILE__); break;
}
}
const device_type CHANNELF = &device_creator<channelf_sound_device>;
channelf_sound_device::channelf_sound_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
: device_t(mconfig, CHANNELF, "Channel F", tag, owner, clock),
device_sound_interface(mconfig, *this)
{
m_token = global_alloc_array_clear(UINT8, sizeof(channelf_sound_state));
}
//-------------------------------------------------
// device_config_complete - perform any
// operations now that the configuration is
// complete
//-------------------------------------------------
void channelf_sound_device::device_config_complete()
{
}
//-------------------------------------------------
// device_start - device-specific startup
//-------------------------------------------------
void channelf_sound_device::device_start()
{
DEVICE_START_NAME( channelf_sound )(this);
}
//-------------------------------------------------
// sound_stream_update - handle a stream update
//-------------------------------------------------
void channelf_sound_device::sound_stream_update(sound_stream &stream, stream_sample_t **inputs, stream_sample_t **outputs, int samples)
{
// should never get here
fatalerror("sound_stream_update called; not applicable to legacy sound devices\n");
}
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