/* Generates a constant square wave sound with a given frequency in Hertz for
a duration in milliseconds */
void beep_play(unsigned int frequency, unsigned int duration,
unsigned int amplitude)
{
mixer_channel_stop(PCM_MIXER_CHAN_BEEP);
if (frequency == 0 || duration == 0 || amplitude == 0)
return;
if (amplitude > INT16_MAX)
amplitude = INT16_MAX;
/* Setup the parameters for the square wave generator */
beep_phase = 0;
beep_step = 0xffffffffu / NATIVE_FREQUENCY * frequency;
beep_count = NATIVE_FREQUENCY / 1000 * duration;
#ifdef BEEP_GENERIC
beep_amplitude = amplitude;
#else
/* Optimized routines do XOR with phase sign bit in both channels at once */
beep_amplitude = amplitude | (amplitude << 16); /* Word:|AMP16|AMP16| */
#endif
/* If it fits - avoid cb overhead */
const void *start;
size_t size;
/* Generate first frame here */
beep_get_more(&start, &size);
mixer_channel_set_amplitude(PCM_MIXER_CHAN_BEEP, MIX_AMP_UNITY);
mixer_channel_play_data(PCM_MIXER_CHAN_BEEP,
beep_count ? beep_get_more : NULL,
start, size);
}
/* Start playback of voice channel if not already playing */
static void voice_start_playback(void)
{
if (mixer_channel_status(PCM_MIXER_CHAN_VOICE) != CHANNEL_STOPPED)
return;
unsigned int i = cur_buf_out % VOICE_FRAMES;
mixer_channel_play_data(PCM_MIXER_CHAN_VOICE, voice_pcm_callback,
(unsigned char *)voicebuf[i], voicebuf_sizes[i]);
}
