*
* u-law, A-law and linear PCM conversions.
*/
-#define SIGN_BIT (0x80) /* Sign bit for a A-law byte. */
-#define QUANT_MASK (0xf) /* Quantization field mask. */
-#define NSEGS (8) /* Number of A-law segments. */
-#define SEG_SHIFT (4) /* Left shift for segment number. */
-#define SEG_MASK (0x70) /* Segment field mask. */
+#define SIGN_BIT (0x80) /* Sign bit for a A-law byte. */
+#define QUANT_MASK (0xf) /* Quantization field mask. */
+#define NSEGS (8) /* Number of A-law segments. */
+#define SEG_SHIFT (4) /* Left shift for segment number. */
+#define SEG_MASK (0x70) /* Segment field mask. */
static short seg_end[8] = {0xFF, 0x1FF, 0x3FF, 0x7FF,
- 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF};
+ 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF};
/* copy from CCITT G.711 specifications */
-unsigned char _u2a[128] = { /* u- to A-law conversions */
- 1, 1, 2, 2, 3, 3, 4, 4,
- 5, 5, 6, 6, 7, 7, 8, 8,
- 9, 10, 11, 12, 13, 14, 15, 16,
- 17, 18, 19, 20, 21, 22, 23, 24,
- 25, 27, 29, 31, 33, 34, 35, 36,
- 37, 38, 39, 40, 41, 42, 43, 44,
- 46, 48, 49, 50, 51, 52, 53, 54,
- 55, 56, 57, 58, 59, 60, 61, 62,
- 64, 65, 66, 67, 68, 69, 70, 71,
- 72, 73, 74, 75, 76, 77, 78, 79,
- 81, 82, 83, 84, 85, 86, 87, 88,
- 89, 90, 91, 92, 93, 94, 95, 96,
- 97, 98, 99, 100, 101, 102, 103, 104,
- 105, 106, 107, 108, 109, 110, 111, 112,
- 113, 114, 115, 116, 117, 118, 119, 120,
- 121, 122, 123, 124, 125, 126, 127, 128};
+unsigned char _u2a[128] = { /* u- to A-law conversions */
+ 1, 1, 2, 2, 3, 3, 4, 4,
+ 5, 5, 6, 6, 7, 7, 8, 8,
+ 9, 10, 11, 12, 13, 14, 15, 16,
+ 17, 18, 19, 20, 21, 22, 23, 24,
+ 25, 27, 29, 31, 33, 34, 35, 36,
+ 37, 38, 39, 40, 41, 42, 43, 44,
+ 46, 48, 49, 50, 51, 52, 53, 54,
+ 55, 56, 57, 58, 59, 60, 61, 62,
+ 64, 65, 66, 67, 68, 69, 70, 71,
+ 72, 73, 74, 75, 76, 77, 78, 79,
+ 81, 82, 83, 84, 85, 86, 87, 88,
+ 89, 90, 91, 92, 93, 94, 95, 96,
+ 97, 98, 99, 100, 101, 102, 103, 104,
+ 105, 106, 107, 108, 109, 110, 111, 112,
+ 113, 114, 115, 116, 117, 118, 119, 120,
+ 121, 122, 123, 124, 125, 126, 127, 128};
-unsigned char _a2u[128] = { /* A- to u-law conversions */
- 1, 3, 5, 7, 9, 11, 13, 15,
- 16, 17, 18, 19, 20, 21, 22, 23,
- 24, 25, 26, 27, 28, 29, 30, 31,
- 32, 32, 33, 33, 34, 34, 35, 35,
- 36, 37, 38, 39, 40, 41, 42, 43,
- 44, 45, 46, 47, 48, 48, 49, 49,
- 50, 51, 52, 53, 54, 55, 56, 57,
- 58, 59, 60, 61, 62, 63, 64, 64,
- 65, 66, 67, 68, 69, 70, 71, 72,
- 73, 74, 75, 76, 77, 78, 79, 79,
- 80, 81, 82, 83, 84, 85, 86, 87,
- 88, 89, 90, 91, 92, 93, 94, 95,
- 96, 97, 98, 99, 100, 101, 102, 103,
- 104, 105, 106, 107, 108, 109, 110, 111,
- 112, 113, 114, 115, 116, 117, 118, 119,
- 120, 121, 122, 123, 124, 125, 126, 127};
+unsigned char _a2u[128] = { /* A- to u-law conversions */
+ 1, 3, 5, 7, 9, 11, 13, 15,
+ 16, 17, 18, 19, 20, 21, 22, 23,
+ 24, 25, 26, 27, 28, 29, 30, 31,
+ 32, 32, 33, 33, 34, 34, 35, 35,
+ 36, 37, 38, 39, 40, 41, 42, 43,
+ 44, 45, 46, 47, 48, 48, 49, 49,
+ 50, 51, 52, 53, 54, 55, 56, 57,
+ 58, 59, 60, 61, 62, 63, 64, 64,
+ 65, 66, 67, 68, 69, 70, 71, 72,
+ 73, 74, 75, 76, 77, 78, 79, 79,
+ 80, 81, 82, 83, 84, 85, 86, 87,
+ 88, 89, 90, 91, 92, 93, 94, 95,
+ 96, 97, 98, 99, 100, 101, 102, 103,
+ 104, 105, 106, 107, 108, 109, 110, 111,
+ 112, 113, 114, 115, 116, 117, 118, 119,
+ 120, 121, 122, 123, 124, 125, 126, 127};
static int
search(
- int val,
- short *table,
- int size)
+ int val,
+ short *table,
+ int size)
{
- int i;
+ int i;
- for (i = 0; i < size; i++) {
- if (val <= *table++)
- return (i);
- }
- return (size);
+ for (i = 0; i < size; i++) {
+ if (val <= *table++)
+ return (i);
+ }
+ return (size);
}
/*
*
* linear2alaw() accepts an 16-bit integer and encodes it as A-law data.
*
- * Linear Input Code Compressed Code
- * ------------------------ ---------------
- * 0000000wxyza 000wxyz
- * 0000001wxyza 001wxyz
- * 000001wxyzab 010wxyz
- * 00001wxyzabc 011wxyz
- * 0001wxyzabcd 100wxyz
- * 001wxyzabcde 101wxyz
- * 01wxyzabcdef 110wxyz
- * 1wxyzabcdefg 111wxyz
+ * Linear Input Code Compressed Code
+ * ------------------------ ---------------
+ * 0000000wxyza 000wxyz
+ * 0000001wxyza 001wxyz
+ * 000001wxyzab 010wxyz
+ * 00001wxyzabc 011wxyz
+ * 0001wxyzabcd 100wxyz
+ * 001wxyzabcde 101wxyz
+ * 01wxyzabcdef 110wxyz
+ * 1wxyzabcdefg 111wxyz
*
* For further information see John C. Bellamy's Digital Telephony, 1982,
* John Wiley & Sons, pps 98-111 and 472-476.
*/
unsigned char
linear2alaw(
- int pcm_val) /* 2's complement (16-bit range) */
+ int pcm_val) /* 2's complement (16-bit range) */
{
- int mask;
- int seg;
- unsigned char aval;
+ int mask;
+ int seg;
+ unsigned char aval;
- if (pcm_val >= 0) {
- mask = 0xD5; /* sign (7th) bit = 1 */
- } else {
- mask = 0x55; /* sign bit = 0 */
- pcm_val = -pcm_val - 8;
- }
+ if (pcm_val >= 0) {
+ mask = 0xD5; /* sign (7th) bit = 1 */
+ } else {
+ mask = 0x55; /* sign bit = 0 */
+ pcm_val = -pcm_val - 8;
+ }
- /* Convert the scaled magnitude to segment number. */
- seg = search(pcm_val, seg_end, 8);
+ /* Convert the scaled magnitude to segment number. */
+ seg = search(pcm_val, seg_end, 8);
- /* Combine the sign, segment, and quantization bits. */
+ /* Combine the sign, segment, and quantization bits. */
- if (seg >= 8) /* out of range, return maximum value. */
- return (0x7F ^ mask);
- else {
- aval = seg << SEG_SHIFT;
- if (seg < 2)
- aval |= (pcm_val >> 4) & QUANT_MASK;
- else
- aval |= (pcm_val >> (seg + 3)) & QUANT_MASK;
- return (aval ^ mask);
- }
+ if (seg >= 8) /* out of range, return maximum value. */
+ return (0x7F ^ mask);
+ else {
+ aval = seg << SEG_SHIFT;
+ if (seg < 2)
+ aval |= (pcm_val >> 4) & QUANT_MASK;
+ else
+ aval |= (pcm_val >> (seg + 3)) & QUANT_MASK;
+ return (aval ^ mask);
+ }
}
/*
*/
int
alaw2linear(
- unsigned char a_val)
+ unsigned char a_val)
{
- int t;
- int seg;
+ int t;
+ int seg;
- a_val ^= 0x55;
+ a_val ^= 0x55;
- t = (a_val & QUANT_MASK) << 4;
- seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
- switch (seg) {
- case 0:
- t += 8;
- break;
- case 1:
- t += 0x108;
- break;
- default:
- t += 0x108;
- t <<= seg - 1;
- }
- return ((a_val & SIGN_BIT) ? t : -t);
+ t = (a_val & QUANT_MASK) << 4;
+ seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
+ switch (seg) {
+ case 0:
+ t += 8;
+ break;
+ case 1:
+ t += 0x108;
+ break;
+ default:
+ t += 0x108;
+ t <<= seg - 1;
+ }
+ return ((a_val & SIGN_BIT) ? t : -t);
}
-#define BIAS (0x84) /* Bias for linear code. */
+#define BIAS (0x84) /* Bias for linear code. */
/*
* linear2ulaw() - Convert a linear PCM value to u-law
* is biased by adding 33 which shifts the encoding range from (0 - 8158) to
* (33 - 8191). The result can be seen in the following encoding table:
*
- * Biased Linear Input Code Compressed Code
- * ------------------------ ---------------
- * 00000001wxyza 000wxyz
- * 0000001wxyzab 001wxyz
- * 000001wxyzabc 010wxyz
- * 00001wxyzabcd 011wxyz
- * 0001wxyzabcde 100wxyz
- * 001wxyzabcdef 101wxyz
- * 01wxyzabcdefg 110wxyz
- * 1wxyzabcdefgh 111wxyz
+ * Biased Linear Input Code Compressed Code
+ * ------------------------ ---------------
+ * 00000001wxyza 000wxyz
+ * 0000001wxyzab 001wxyz
+ * 000001wxyzabc 010wxyz
+ * 00001wxyzabcd 011wxyz
+ * 0001wxyzabcde 100wxyz
+ * 001wxyzabcdef 101wxyz
+ * 01wxyzabcdefg 110wxyz
+ * 1wxyzabcdefgh 111wxyz
*
* Each biased linear code has a leading 1 which identifies the segment
* number. The value of the segment number is equal to 7 minus the number
*/
unsigned char
linear2ulaw(
- int pcm_val) /* 2's complement (16-bit range) */
+ int pcm_val) /* 2's complement (16-bit range) */
{
- int mask;
- int seg;
- unsigned char uval;
+ int mask;
+ int seg;
+ unsigned char uval;
- /* Get the sign and the magnitude of the value. */
- if (pcm_val < 0) {
- pcm_val = BIAS - pcm_val;
- mask = 0x7F;
- } else {
- pcm_val += BIAS;
- mask = 0xFF;
- }
+ /* Get the sign and the magnitude of the value. */
+ if (pcm_val < 0) {
+ pcm_val = BIAS - pcm_val;
+ mask = 0x7F;
+ } else {
+ pcm_val += BIAS;
+ mask = 0xFF;
+ }
- /* Convert the scaled magnitude to segment number. */
- seg = search(pcm_val, seg_end, 8);
+ /* Convert the scaled magnitude to segment number. */
+ seg = search(pcm_val, seg_end, 8);
- /*
- * Combine the sign, segment, quantization bits;
- * and complement the code word.
- */
- if (seg >= 8) /* out of range, return maximum value. */
- return (0x7F ^ mask);
- else {
- uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF);
- return (uval ^ mask);
- }
+ /*
+ * Combine the sign, segment, quantization bits;
+ * and complement the code word.
+ */
+ if (seg >= 8) /* out of range, return maximum value. */
+ return (0x7F ^ mask);
+ else {
+ uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF);
+ return (uval ^ mask);
+ }
}
*/
int
ulaw2linear(
- unsigned char u_val)
+ unsigned char u_val)
{
- int t;
+ int t;
- /* Complement to obtain normal u-law value. */
- u_val = ~u_val;
+ /* Complement to obtain normal u-law value. */
+ u_val = ~u_val;
- /*
- * Extract and bias the quantization bits. Then
- * shift up by the segment number and subtract out the bias.
- */
- t = ((u_val & QUANT_MASK) << 3) + BIAS;
- t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
+ /*
+ * Extract and bias the quantization bits. Then
+ * shift up by the segment number and subtract out the bias.
+ */
+ t = ((u_val & QUANT_MASK) << 3) + BIAS;
+ t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
- return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));
+ return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));
}
/* A-law to u-law conversion */
unsigned char
alaw2ulaw(
- unsigned char aval)
+ unsigned char aval)
{
- aval &= 0xff;
- return ((aval & 0x80) ? (0xFF ^ _a2u[aval ^ 0xD5]) :
- (0x7F ^ _a2u[aval ^ 0x55]));
+ aval &= 0xff;
+ return ((aval & 0x80) ? (0xFF ^ _a2u[aval ^ 0xD5]) :
+ (0x7F ^ _a2u[aval ^ 0x55]));
}
/* u-law to A-law conversion */
unsigned char
ulaw2alaw(
- unsigned char uval)
+ unsigned char uval)
{
- uval &= 0xff;
- return ((uval & 0x80) ? (0xD5 ^ (_u2a[0xFF ^ uval] - 1)) :
- (0x55 ^ (_u2a[0x7F ^ uval] - 1)));
+ uval &= 0xff;
+ return ((uval & 0x80) ? (0xD5 ^ (_u2a[0xFF ^ uval] - 1)) :
+ (0x55 ^ (_u2a[0x7F ^ uval] - 1)));
}
projects / wxWidgets.git / blobdiff