double speaker_sound_device::update_interm_samples_get_filtered_volume(int volume)
{
double filtered_volume, tempx;
/* We may have one or more interm. samples to go */
if (m_interm_sample_index < RATE_MULTIPLIER)
{
/* First interm. sample may be composed. */
finalize_interm_sample(volume);
/* Subsequent interm. samples will be homogeneous. */
while (m_interm_sample_index + 1 < RATE_MULTIPLIER)
{
init_next_interm_sample();
m_composed_volume[m_composed_sample_index] = volume;
}
}
/* Important: next interm. sample not initialised yet, so that no data is destroyed before filtering... */
filtered_volume = get_filtered_volume();
init_next_interm_sample();
/* Reset counter to next stream sample: */
m_interm_sample_index = 0;
/* simple DC blocker filter */
tempx = filtered_volume;
filtered_volume = tempx - m_prevx + 0.995 * m_prevy;
m_prevx = tempx;
m_prevy = filtered_volume;
return filtered_volume;
}
static double update_interm_samples_get_filtered_volume(speaker_state *sp, int volume)
{
double filtered_volume;
/* We may have one or more interm. samples to go */
if (sp->interm_sample_index < RATE_MULTIPLIER)
{
/* First interm. sample may be composed. */
finalize_interm_sample(sp, volume);
/* Subsequent interm. samples will be homogeneous. */
while (sp->interm_sample_index + 1 < RATE_MULTIPLIER)
{
init_next_interm_sample(sp);
sp->composed_volume[sp->composed_sample_index] = volume;
}
}
/* Important: next interm. sample not initialised yet, so that no data is destroyed before filtering... */
filtered_volume = get_filtered_volume(sp);
init_next_interm_sample(sp);
/* Reset counter to next stream sample: */
sp->interm_sample_index = 0;
return filtered_volume;
}
void speaker_sound_device::update_interm_samples(attotime time, int volume)
{
double fraction;
/* We may have completed zero, one or more interm. samples: */
while (time >= m_next_interm_sample_time)
{
/* First interm. sample may be composed, subsequent samples will be homogeneous. */
/* Treat all the same general way. */
finalize_interm_sample(volume);
init_next_interm_sample();
}
/* Depending on status above:
* a) Add latest fraction to unfinished composed sample
* b) The overshooting fraction of time will start a new composed sample
*/
fraction = make_fraction(time, m_last_update_time, m_interm_sample_period_secfrac);
m_composed_volume[m_composed_sample_index] += volume * fraction;
m_last_update_time = time;
}