local.media
Class G711

java.lang.Object
  |
  +--local.media.G711

public class G711

extends java.lang.Object

G.711 codec. This class provides methods for u-law, A-law and linear PCM conversions.

Field Summary

static int

BIAS Bias for linear code.

Constructor Summary

G711()

Method Summary

static int	alaw2linear(int a_val) Converts an A-law value to 16-bit linear PCM
static int	alaw2ulaw(int aval) A-law to u-law conversion.
static int	linear2alaw(int pcm_val) Converts a 16-bit linear PCM value to 8-bit A-law.
static int	linear2ulaw(int pcm_val) 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).
static int	ulaw2alaw(int uval) u-law to A-law conversion.
static int	ulaw2linear(int u_val) ConvertS a u-law value to 16-bit linear PCM.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

BIAS

public static final int BIAS

Bias for linear code.

Constructor Detail

G711

public G711()

Method Detail

linear2alaw

public static int linear2alaw(int pcm_val)

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.

alaw2linear

public static int alaw2linear(int a_val)

Converts an A-law value to 16-bit linear PCM

linear2ulaw

public static int linear2ulaw(int pcm_val)

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.

ulaw2linear

public static int ulaw2linear(int u_val)

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.

alaw2ulaw

public static int alaw2ulaw(int aval)

A-law to u-law conversion.

ulaw2alaw

public static int ulaw2alaw(int uval)

u-law to A-law conversion.