* These routines comprise an implementation of the CCITT G.726 32kbps ADPCM * coding algorithm. Essentially, this implementation is identical to * the bit level description except for a few deviations which * take advantage of work station attributes, such as hardware 2's * complement arithmetic and large memory. Specifically, certain time * consuming operations such as multiplications are replaced * with lookup tables and software 2's complement operations are * replaced with hardware 2's complement. *
* The deviation from the bit level specification (lookup tables) * preserves the bit level performance specifications. *
* As outlined in the G.726 Recommendation, the algorithm is broken * down into modules. Each section of code below is preceded by * the name of the module which it is implementing. *
* This implementation is based on the ANSI-C language reference implementations * of the CCITT (International Telegraph and Telephone Consultative Committee) * G.711, G.721 and G.723 voice compressions, provided by Sun Microsystems, Inc. *
* Acknowledgement to Sun Microsystems, Inc. for having released the original
* ANSI-C source code to the public domain.
*/
public class G726_32 extends G726 {
// ##### C-to-Java conversion: #####
// short becomes int
// char becomes int
// unsigned char becomes int
// *************************** STATIC ***************************
static /*short*/int[] qtab_721={-124, 80, 178, 246, 300, 349, 400};
/*
* Maps G726_32 code word to reconstructed scale factor normalized log
* magnitude values.
*/
static /*short*/int[] _dqlntab={-2048, 4, 135, 213, 273, 323, 373, 425, 425, 373, 323, 273, 213, 135, 4, -2048};
/* Maps G726_32 code word to log of scale factor multiplier. */
static /*short*/int[] _witab={-12, 18, 41, 64, 112, 198, 355, 1122, 1122, 355, 198, 112, 64, 41, 18, -12};
/*
* Maps G726_32 code words to a set of values whose long and short
* term averages are computed and then compared to give an indication
* how stationary (steady state) the signal is.
*/
static /*short*/int[] _fitab={0, 0, 0, 0x200, 0x200, 0x200, 0x600, 0xE00, 0xE00, 0x600, 0x200, 0x200, 0x200, 0, 0, 0};
/** Encodes the input vale of linear PCM, A-law or u-law data sl and returns
* the resulting code. -1 is returned for unknown input coding value. */
public static int encode(int sl, int in_coding, G726State state) {
/*short*/int sezi, se, sez; /* ACCUM */
/*short*/int d; /* SUBTA */
/*short*/int sr; /* ADDB */
/*short*/int y; /* MIX */
/*short*/int dqsez; /* ADDC */
/*short*/int dq, i;
switch (in_coding) {
/* linearize input sample to 14-bit PCM */
case AUDIO_ENCODING_ALAW:
sl= G711Codec.alaw2linear((byte)sl) >> 2;
break;
case AUDIO_ENCODING_ULAW:
sl= G711UCodec.ulaw2linear((byte)sl) >> 2;
break;
case AUDIO_ENCODING_LINEAR:
sl >>= 2; /* 14-bit dynamic range */
break;
default:
return -1;
}
sezi=state.predictor_zero();
sez=sezi >> 1;
se=(sezi+state.predictor_pole()) >> 1; /* estimated signal */
d=sl-se; /* estimation difference */
/* quantize the prediction difference */
y=state.step_size(); /* quantizer step size */
i=quantize(d, y, qtab_721, 7); /* i=ADPCM code */
dq=reconstruct(i & 8, _dqlntab[i], y); /* quantized est diff */
sr=(dq<0)? se-(dq & 0x3FFF) : se+dq; /* reconst. signal */
dqsez=sr+sez-se; /* pole prediction diff. */
update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state);
return i;
}
/** Decodes a 4-bit code of G726_32 encoded data of i and
* returns the resulting linear PCM, A-law or u-law value.
* return -1 for unknown out_coding value. */
public static int decode(int i, int out_coding, G726State state) {
/*short*/int sezi, sei, sez, se; /* ACCUM */
/*short*/int y; /* MIX */
/*short*/int sr; /* ADDB */
/*short*/int dq;
/*short*/int dqsez;
i &= 0x0f; /* mask to get proper bits */
sezi=state.predictor_zero();
sez=sezi >> 1;
sei=sezi+state.predictor_pole();
se=sei >> 1; /* se=estimated signal */
y=state.step_size(); /* dynamic quantizer step size */
dq=reconstruct(i & 0x08, _dqlntab[i], y); /* quantized diff. */
sr=(dq<0)? (se-(dq & 0x3FFF)) : se+dq; /* reconst. signal */
dqsez=sr-se+sez; /* pole prediction diff. */
update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state);
switch (out_coding) {
case AUDIO_ENCODING_ALAW:
return (tandem_adjust_alaw(sr, se, y, i, 8, qtab_721));
case AUDIO_ENCODING_ULAW:
return (tandem_adjust_ulaw(sr, se, y, i, 8, qtab_721));
case AUDIO_ENCODING_LINEAR:
return (sr << 2); /* sr was 14-bit dynamic range */
default:
return -1;
}
}
/** Encodes the input chunk in_buff of linear PCM, A-law or u-law data and returns
* the G726_32 encoded chuck into out_buff.
* It returns the actual size of the output data, or -1 in case of unknown
* in_coding value. */
public static int encode(byte[] in_buff, int in_offset, int in_len, int in_coding, byte[] out_buff, int out_offset, G726State state) {
if (in_coding==AUDIO_ENCODING_ALAW || in_coding==AUDIO_ENCODING_ULAW) {
/*
for (int i=0; i
* It returns the actual size of the output data, or -1 in case of unknown
* in_coding value. */
public int encode(byte[] in_buff, int in_offset, int in_len, int in_coding, byte[] out_buff, int out_offset) {
return encode(in_buff,in_offset,in_len,in_coding,out_buff,out_offset,state);
}
/** Decodes a 4-bit code of G726_32 encoded data of i and
* returns the resulting linear PCM, A-law or u-law value.
* return -1 for unknown out_coding value. */
public int decode(int i, int out_coding) {
return decode(i,out_coding,state);
}
/** Decodes the input chunk in_buff of G726_32 encoded data and returns
* the linear PCM, A-law or u-law chunk into out_buff.
* It returns the actual size of the output data, or -1 in case of unknown
* out_coding value. */
public int decode(byte[] in_buff, int in_offset, int in_len, int out_coding, byte[] out_buff, int out_offset) {
return decode(in_buff,in_offset,in_len,out_coding,out_buff,out_offset,state);
}
}