package local.media;
/** G.711 codec.
* This class provides methods for u-law, A-law and linear PCM conversions.
*/
public class G711
{
static final int SIGN_BIT=0x80; // Sign bit for a A-law byte.
static final int QUANT_MASK=0xf; // Quantization field mask.
static final int NSEGS=8; // Number of A-law segments.
static final int SEG_SHIFT=4; // Left shift for segment number.
static final int SEG_MASK=0x70; // Segment field mask.
static final int[] seg_end={ 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF };
// copy from CCITT G.711 specifications
/** u- to A-law conversions */
static final int[] _u2a={
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 };
/** A- to u-law conversions */
static final int[] _a2u={
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, int[] table)
{ for (int i=0; i<table.length; i++) if (val<=table[i]) return i;
return table.length;
}
/** Converts a 16-bit linear PCM value to 8-bit A-law.
*
* It 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
*
* For further information see John C. Bellamy's Digital Telephony, 1982,
* John Wiley & Sons, pps 98-111 and 472-476.
*/
public static int linear2alaw(int pcm_val) // 2's complement (16-bit range)
{ int mask;
int seg;
//unsigned char aval;
int aval;
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);
// 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);
}
}
/** Converts an A-law value to 16-bit linear PCM
*/
//public static int alaw2linear(unsigned char a_val)
public static int alaw2linear(int a_val)
{ int t;
int seg;
a_val^=0x55;
t=(a_val&QUANT_MASK)<<4;
//seg=((unsigned)a_val&SEG_MASK)>>SEG_SHIFT;
seg=(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)!=0)? t : -t;
}
/** Bias for linear code. */
public static final int BIAS=0x84;
/** Converts a linear PCM value to u-law
*
* In order to simplify the encoding process, the original linear magnitude
* 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
*
* 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
* of leading 0's. The quantization interval is directly available as the
* four bits wxyz. The trailing bits (a - h) are ignored.
*
* Ordinarily the complement of the resulting code word is used for
* transmission, and so the code word is complemented before it is returned.
*
* For further information see John C. Bellamy's Digital Telephony, 1982,
* John Wiley & Sons, pps 98-111 and 472-476.
*/
public static int linear2ulaw(int pcm_val) // 2's complement (16-bit range)
{ int mask;
int seg;
//unsigned char uval;
int 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;
}
// Convert the scaled magnitude to segment number.
seg=search(pcm_val,seg_end);
// Combine the sign, segment, quantization bits; and complement the code word.
if (seg>=8) return (0x7F^mask); // out of range, return maximum value.
else
{ uval=(seg<<4) | ((pcm_val>>(seg+3)) & 0xF);
return (uval^mask);
}
}
/** ConvertS a u-law value to 16-bit linear PCM.
*
* First, a biased linear code is derived from the code word. An unbiased
* output can then be obtained by subtracting 33 from the biased code.
*
* Note that this function expects to be passed the complement of the
* original code word. This is in keeping with ISDN conventions.
*/
//public static int ulaw2linear(unsigned char u_val)
public static int ulaw2linear(int u_val)
{ int t;
// 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;
t<<=(u_val&SEG_MASK)>>SEG_SHIFT;
return ((u_val&SIGN_BIT)!=0)? (BIAS-t) : (t-BIAS);
}
/** A-law to u-law conversion.
*/
//public static int alaw2ulaw(unsigned char aval)
public static int alaw2ulaw(int aval)
{ aval&=0xff;
return ((aval & 0x80)!=0)? (0xFF^_a2u[aval^0xD5]) : (0x7F^_a2u[aval^0x55]);
}
/** u-law to A-law conversion.
*/
//public static int ulaw2alaw(unsigned char uval)
public static int ulaw2alaw(int uval)
{ uval&=0xff;
return ((uval&0x80)!=0)? (0xD5^(_u2a[0xFF^uval]-1)) : (0x55^(_u2a[0x7F^uval]-1));
}
/** PCM ecoder/decoder tests. */
/*public static void main(String[] args)
{
for (int i=0; i<0xFF; i++)
{ int pcmu,pcma,linear;
pcmu=i;
System.out.print(" pcmu:"+pcmu);
pcma=ulaw2alaw(pcmu);
System.out.print(" pcma:"+pcma);
pcmu=alaw2ulaw(pcma);
System.out.print(" pcmu:"+pcmu);
linear=alaw2linear(pcma);
System.out.print(" linear:"+linear);
pcma=linear2alaw(linear);
System.out.print(" pcma:"+pcma);
linear=ulaw2linear(pcmu);
System.out.print(" linear:"+linear);
pcmu=linear2ulaw(linear);
System.out.print(" pcmu:"+pcmu);
System.out.println(" .");
if (i%20==19)
try { System.in.read(); } catch (Exception e) {}
}
}*/
}