AudioPlayMemory using u-law and simpler header

Audio.cpp

 	uint32_t format;
 
 	playing = 0;
-	length = *data++;
+	prior = 0;
 	format = *data++;
 	next = data;
-	prior = 0;
-	if (format == (44100 | (8 << 24))) {
-		playing = 1;
-	} else if (format == (44100 | (16 << 24))) {
-		playing = 2;
-	} else if (format == (22050 | (8 << 24))) {
-		playing = 3;
-	} else if (format == (22050 | (16 << 24))) {
-		playing = 4;
-	} else if (format == (11025 | (8 << 24))) {
-		playing = 5;
-	} else if (format == (11025 | (16 << 24))) {
-		playing = 6;
-	} else if (format == (8000 | (8 << 24))) {
-		playing = 7;
-	}
+	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)
 {
 	s0 = prior;
 
 	switch (playing) {
-	  case 1: // 8 bits, 44100 Hz - works
+	  case 0x01: // u-law encoded, 44100 Hz
 		for (i=0; i < AUDIO_BLOCK_SAMPLES; i += 4) {
 			tmp32 = *in++;
-			*out++ = (int8_t)(tmp32 & 255) << 8;
-			*out++ = (int8_t)((tmp32 >> 8) & 255) << 8;
-			*out++ = (int8_t)((tmp32 >> 16) & 255) << 8;
-			*out++ = (int8_t)((tmp32 >> 24) & 255) << 8;
+			*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 2: // 16 bits, 44100 Hz - ???
+	  case 0x81: // 16 bit PCM, 44100 Hz
 		for (i=0; i < AUDIO_BLOCK_SAMPLES; i += 2) {
 			tmp32 = *in++;
 			*out++ = (int16_t)(tmp32 & 65535);
 		consumed = 128;
 		break;
 
-	  case 3: // 8 bits, 22050 Hz - works
+	  case 0x02: // u-law encoded, 22050 Hz 
 		for (i=0; i < AUDIO_BLOCK_SAMPLES; i += 8) {
 			tmp32 = *in++;
-			s1 = (int8_t)((tmp32 >> 0) & 255) << 8;
-			s2 = (int8_t)((tmp32 >> 8) & 255) << 8;
-			s3 = (int8_t)((tmp32 >> 16) & 255) << 8;
-			s4 = (int8_t)((tmp32 >> 24) & 255) << 8;
+			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;
 		consumed = 64;
 		break;
 
-	  case 4: // 16 bits, 22050 Hz - ??
+	  case 0x82: // 16 bits PCM, 22050 Hz
 		for (i=0; i < AUDIO_BLOCK_SAMPLES; i += 4) {
 			tmp32 = *in++;
 			s1 = (int16_t)(tmp32 & 65535);
 		consumed = 64;
 		break;
 
-	  case 5: // 8 bits, 11025 Hz - ??
+	  case 0x03: // u-law encoded, 11025 Hz
 		for (i=0; i < AUDIO_BLOCK_SAMPLES; i += 16) {
 			tmp32 = *in++;
-			s1 = (int8_t)((tmp32 >> 0) & 255) << 8;
-			s2 = (int8_t)((tmp32 >> 8) & 255) << 8;
-			s3 = (int8_t)((tmp32 >> 16) & 255) << 8;
-			s4 = (int8_t)((tmp32 >> 24) & 255) << 8;
+			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;
 		consumed = 32;
 		break;
 
-	  case 6: // 16 bits, 11025 Hz - ??
+	  case 0x83: // 16 bit PCM, 11025 Hz
 		for (i=0; i < AUDIO_BLOCK_SAMPLES; i += 8) {
 			tmp32 = *in++;
 			s1 = (int16_t)(tmp32 & 65535);

Audio.h

 	const unsigned int *next;
 	uint32_t length;
 	int16_t prior;
-	uint8_t playing;
+	volatile uint8_t playing;
 };
 
 

ulaw.c

 #include <stdint.h>
 
+
+const int16_t ulaw_decode_table[256] = {
+     4,    12,    20,    28,    36,    44,    52,    60,    68,    76,
+    84,    92,   100,   108,   116,   124,   136,   152,   168,   184,
+   200,   216,   232,   248,   264,   280,   296,   312,   328,   344,
+   360,   376,   400,   432,   464,   496,   528,   560,   592,   624,
+   656,   688,   720,   752,   784,   816,   848,   880,   928,   992,
+  1056,  1120,  1184,  1248,  1312,  1376,  1440,  1504,  1568,  1632,
+  1696,  1760,  1824,  1888,  1984,  2112,  2240,  2368,  2496,  2624,
+  2752,  2880,  3008,  3136,  3264,  3392,  3520,  3648,  3776,  3904,
+  4096,  4352,  4608,  4864,  5120,  5376,  5632,  5888,  6144,  6400,
+  6656,  6912,  7168,  7424,  7680,  7936,  8320,  8832,  9344,  9856,
+ 10368, 10880, 11392, 11904, 12416, 12928, 13440, 13952, 14464, 14976,
+ 15488, 16000, 16768, 17792, 18816, 19840, 20864, 21888, 22912, 23936,
+ 24960, 25984, 27008, 28032, 29056, 30080, 31104, 32128,    -4,   -12,
+   -20,   -28,   -36,   -44,   -52,   -60,   -68,   -76,   -84,   -92,
+  -100,  -108,  -116,  -124,  -136,  -152,  -168,  -184,  -200,  -216,
+  -232,  -248,  -264,  -280,  -296,  -312,  -328,  -344,  -360,  -376,
+  -400,  -432,  -464,  -496,  -528,  -560,  -592,  -624,  -656,  -688,
+  -720,  -752,  -784,  -816,  -848,  -880,  -928,  -992, -1056, -1120,
+ -1184, -1248, -1312, -1376, -1440, -1504, -1568, -1632, -1696, -1760,
+ -1824, -1888, -1984, -2112, -2240, -2368, -2496, -2624, -2752, -2880,
+ -3008, -3136, -3264, -3392, -3520, -3648, -3776, -3904, -4096, -4352,
+ -4608, -4864, -5120, -5376, -5632, -5888, -6144, -6400, -6656, -6912,
+ -7168, -7424, -7680, -7936, -8320, -8832, -9344, -9856,-10368,-10880,
+-11392,-11904,-12416,-12928,-13440,-13952,-14464,-14976,-15488,-16000,
+-16768,-17792,-18816,-19840,-20864,-21888,-22912,-23936,-24960,-25984,
+-27008,-28032,-29056,-30080,-31104,-32128
+};
+/*
+#! /usr/bin/perl
+print "const int16_t ulaw_decode_table[256] = {\n";
+for ($i=0; $i < 256; $i++) {
+	$r = ($i >> 4) & 7;
+	$n = ($i & 0xF) << ($r + 3);
+	$n |= 1 << ($r + 7);
+	$n |= 1 << ($r + 2);
+	$n -= 128;
+	$n *= -1 if $i > 127;
+        printf "%6d", $n + 0;
+        print "," if ($i < 255);
+        print "\n" if ($i % 10) == 9;
+}
+print "\n};\n";
+*/
+
+
+
+/*
 const int16_t ulaw_decode_table[256] = {
      0,     8,    16,    24,    32,    40,    48,    56,    64,    72,
     80,    88,    96,   104,   112,   120,   128,   144,   160,   176,
 -16256,-17280,-18304,-19328,-20352,-21376,-22400,-23424,-24448,-25472,
 -26496,-27520,-28544,-29568,-30592,-31616
 };
+*/
 /*
 #! /usr/bin/perl
 print "const int16_t ulaw_decode_table[256] = {\n";