teensy-audio/play_memory.cpp

#include "Audio.h"
#include "arm_math.h"
#include "utility/dspinst.h"



void AudioPlayMemory::play(const unsigned int *data)
{
	uint32_t format;

	playing = 0;
	prior = 0;
	format = *data++;
	next = data;
	length = format & 0xFFFFFF;
	playing = format >> 24;
}

void AudioPlayMemory::stop(void)
{
	playing = 0;
}

extern "C" {
extern const int16_t ulaw_decode_table[256];
};

void AudioPlayMemory::update(void)
{
	audio_block_t *block;
	const unsigned int *in;
	int16_t *out;
	uint32_t tmp32, consumed;
	int16_t s0, s1, s2, s3, s4;
	int i;

	if (!playing) return;
	block = allocate();
	if (block == NULL) return;

	//Serial.write('.');

	out = block->data;
	in = next;
	s0 = prior;

	switch (playing) {
	  case 0x01: // u-law encoded, 44100 Hz
		for (i=0; i < AUDIO_BLOCK_SAMPLES; i += 4) {
			tmp32 = *in++;
			*out++ = ulaw_decode_table[(tmp32 >> 0) & 255];
			*out++ = ulaw_decode_table[(tmp32 >> 8) & 255];
			*out++ = ulaw_decode_table[(tmp32 >> 16) & 255];
			*out++ = ulaw_decode_table[(tmp32 >> 24) & 255];
		}
		consumed = 128;
		break;

	  case 0x81: // 16 bit PCM, 44100 Hz
		for (i=0; i < AUDIO_BLOCK_SAMPLES; i += 2) {
			tmp32 = *in++;
			*out++ = (int16_t)(tmp32 & 65535);
			*out++ = (int16_t)(tmp32 >> 16);
		}
		consumed = 128;
		break;

	  case 0x02: // u-law encoded, 22050 Hz 
		for (i=0; i < AUDIO_BLOCK_SAMPLES; i += 8) {
			tmp32 = *in++;
			s1 = ulaw_decode_table[(tmp32 >> 0) & 255];
			s2 = ulaw_decode_table[(tmp32 >> 8) & 255];
			s3 = ulaw_decode_table[(tmp32 >> 16) & 255];
			s4 = ulaw_decode_table[(tmp32 >> 24) & 255];
			*out++ = (s0 + s1) >> 1;
			*out++ = s1;
			*out++ = (s1 + s2) >> 1;
			*out++ = s2;
			*out++ = (s2 + s3) >> 1;
			*out++ = s3;
			*out++ = (s3 + s4) >> 1;
			*out++ = s4;
			s0 = s4;
		}
		consumed = 64;
		break;

	  case 0x82: // 16 bits PCM, 22050 Hz
		for (i=0; i < AUDIO_BLOCK_SAMPLES; i += 4) {
			tmp32 = *in++;
			s1 = (int16_t)(tmp32 & 65535);
			s2 = (int16_t)(tmp32 >> 16);
			*out++ = (s0 + s1) >> 1;
			*out++ = s1;
			*out++ = (s1 + s2) >> 1;
			*out++ = s2;
			s0 = s2;
		}
		consumed = 64;
		break;

	  case 0x03: // u-law encoded, 11025 Hz
		for (i=0; i < AUDIO_BLOCK_SAMPLES; i += 16) {
			tmp32 = *in++;
			s1 = ulaw_decode_table[(tmp32 >> 0) & 255];
			s2 = ulaw_decode_table[(tmp32 >> 8) & 255];
			s3 = ulaw_decode_table[(tmp32 >> 16) & 255];
			s4 = ulaw_decode_table[(tmp32 >> 24) & 255];
			*out++ = (s0 * 3 + s1) >> 2;
			*out++ = (s0 + s1)     >> 1;
			*out++ = (s0 + s1 * 3) >> 2;
			*out++ = s1;
			*out++ = (s1 * 3 + s2) >> 2;
			*out++ = (s1 + s2)     >> 1;
			*out++ = (s1 + s2 * 3) >> 2;
			*out++ = s2;
			*out++ = (s2 * 3 + s3) >> 2;
			*out++ = (s2 + s3)     >> 1;
			*out++ = (s2 + s3 * 3) >> 2;
			*out++ = s3;
			*out++ = (s3 * 3 + s4) >> 2;
			*out++ = (s3 + s4)     >> 1;
			*out++ = (s3 + s4 * 3) >> 2;
			*out++ = s4;
			s0 = s4;
		}
		consumed = 32;
		break;

	  case 0x83: // 16 bit PCM, 11025 Hz
		for (i=0; i < AUDIO_BLOCK_SAMPLES; i += 8) {
			tmp32 = *in++;
			s1 = (int16_t)(tmp32 & 65535);
			s2 = (int16_t)(tmp32 >> 16);
			*out++ = (s0 * 3 + s1) >> 2;
			*out++ = (s0 + s1)     >> 1;
			*out++ = (s0 + s1 * 3) >> 2;
			*out++ = s1;
			*out++ = (s1 * 3 + s2) >> 2;
			*out++ = (s1 + s2)     >> 1;
			*out++ = (s1 + s2 * 3) >> 2;
			*out++ = s2;
			s0 = s2;
		}
		consumed = 32;
		break;

	  default:
		release(block);
		playing = 0;
		return;
	}
	prior = s0;
	next = in;
	if (length > consumed) {
		length -= consumed;
	} else {
		playing = 0;
	}
	transmit(block);
	release(block);
}