- static int exp_lut[256] =
- {
- 0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,
- 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
- 5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
- 5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
- 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
- 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
- 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
- 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
- 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
- 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
- 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
- 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
- 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
- 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
- 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
- 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
- };
-
- int sign, exponent, mantissa;
- unsigned char ulawbyte;
-
- /* Get the sample into sign-magnitude. */
- sign = (sample >> 8) & 0x80; /* set aside the sign */
- if (sign != 0)
- sample = -sample; /* get magnitude */
- if (sample > CLIP)
- sample = CLIP; /* clip the magnitude */
-
- /* Convert from 16 bit linear to ulaw. */
- sample = sample + BIAS;
- exponent = exp_lut[( sample >> 7 ) & 0xFF];
- mantissa = ( sample >> ( exponent + 3 ) ) & 0x0F;
- ulawbyte = ~ ( sign | ( exponent << 4 ) | mantissa );
-#ifdef ZEROTRAP
- if (ulawbyte == 0)
- ulawbyte = 0x02; /* optional CCITT trap */
-#endif