Function MxMixSamples

src/mixer.cpp:124–168

}

void MxMixSamples(void *buffer, uint samples)
{
	PerformanceMeasurer framerate(PFE_SOUND);
	static uint last_samples = 0;
	if (samples != last_samples) {
		framerate.SetExpectedRate((double)_play_rate / samples);
		last_samples = samples;
	}

	/* Clear the buffer */
	std::fill_n(static_cast<int16_t *>(buffer), 2 * samples, 0);

	{
		std::lock_guard<std::mutex> lock{ _music_stream_mutex };
		/* Fetch music if a sampled stream is available */
		if (_music_stream) _music_stream((int16_t*)buffer, samples);
	}

	/* Check if any channels should be stopped. */
	MixerChannelMask stop = _stop_channels.load(std::memory_order_acquire);
	for (uint8_t idx : SetBitIterator(stop)) {
		MxCloseChannel(idx);
	}

	/* Apply simple x^3 scaling to master effect volume. This increases the
	 * perceived difference in loudness to better match expectations. effect_vol
	 * is expected to be in the range 0-127 hence the division by 127 * 127 to
	 * get back into range. */
	uint8_t effect_vol_setting = _effect_vol.load(std::memory_order_relaxed);
	uint8_t effect_vol = (effect_vol_setting *
	                    effect_vol_setting *
	                    effect_vol_setting) / (127 * 127);

	/* Mix each channel */
	MixerChannelMask active = _active_channels.load(std::memory_order_acquire);
	for (uint8_t idx : SetBitIterator(active)) {
		MixerChannel *mc = &_channels[idx];
		if (mc->is16bit) {
			mix_int16<int16_t>(mc, (int16_t*)buffer, samples, effect_vol);
		} else {
			mix_int16<int8_t>(mc, (int16_t*)buffer, samples, effect_vol);
		}
		if (mc->samples_left == 0) MxCloseChannel(idx);
	}
}

MixerChannel *MxAllocateChannel()
{