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* This source code is a product of Sun Microsystems, Inc. and is provided
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* for unrestricted use. Users may copy or modify this source code without
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* SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
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* THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
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* Sun source code is provided with no support and without any obligation on
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* the part of Sun Microsystems, Inc. to assist in its use, correction,
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* modification or enhancement.
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* SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
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* INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
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* OR ANY PART THEREOF.
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* In no event will Sun Microsystems, Inc. be liable for any lost revenue
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* or profits or other special, indirect and consequential damages, even if
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* Sun has been advised of the possibility of such damages.
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* Sun Microsystems, Inc.
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* Mountain View, California 94043
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#include "wx/wxprec.h"
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* g721_encoder(), g721_decoder()
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* These routines comprise an implementation of the CCITT G.721 ADPCM
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* coding algorithm. Essentially, this implementation is identical to
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* the bit level description except for a few deviations which
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* take advantage of work station attributes, such as hardware 2's
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* complement arithmetic and large memory. Specifically, certain time
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* consuming operations such as multiplications are replaced
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* with lookup tables and software 2's complement operations are
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* replaced with hardware 2's complement.
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* The deviation from the bit level specification (lookup tables)
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* preserves the bit level performance specifications.
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* As outlined in the G.721 Recommendation, the algorithm is broken
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* down into modules. Each section of code below is preceded by
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* the name of the module which it is implementing.
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#include "wx/mmedia/internal/g72x.h"
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static short qtab_721[7] = {-124, 80, 178, 246, 300, 349, 400};
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* Maps G.721 code word to reconstructed scale factor normalized log
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static short _dqlntab[16] = {-2048, 4, 135, 213, 273, 323, 373, 425,
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425, 373, 323, 273, 213, 135, 4, -2048};
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/* Maps G.721 code word to log of scale factor multiplier. */
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static short _witab[16] = {-12, 18, 41, 64, 112, 198, 355, 1122,
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1122, 355, 198, 112, 64, 41, 18, -12};
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* Maps G.721 code words to a set of values whose long and short
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* term averages are computed and then compared to give an indication
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* how stationary (steady state) the signal is.
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static short _fitab[16] = {0, 0, 0, 0x200, 0x200, 0x200, 0x600, 0xE00,
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0xE00, 0x600, 0x200, 0x200, 0x200, 0, 0, 0};
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* Encodes the input vale of linear PCM, A-law or u-law data sl and returns
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* the resulting code. -1 is returned for unknown input coding value.
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struct g72x_state *state_ptr)
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short sezi, se, sez; /* ACCUM */
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short dqsez; /* ADDC */
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switch (in_coding) { /* linearize input sample to 14-bit PCM */
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case AUDIO_ENCODING_ALAW:
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sl = alaw2linear(sl) >> 2;
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case AUDIO_ENCODING_ULAW:
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sl = ulaw2linear(sl) >> 2;
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case AUDIO_ENCODING_LINEAR:
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sl = ((short)sl) >> 2; /* 14-bit dynamic range */
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sezi = predictor_zero(state_ptr);
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se = (sezi + predictor_pole(state_ptr)) >> 1; /* estimated signal */
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d = sl - se; /* estimation difference */
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/* quantize the prediction difference */
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y = step_size(state_ptr); /* quantizer step size */
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i = quantize(d, y, qtab_721, 7); /* i = ADPCM code */
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dq = reconstruct(i & 8, _dqlntab[i], y); /* quantized est diff */
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sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconst. signal */
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dqsez = sr + sez - se; /* pole prediction diff. */
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update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);
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* Decodes a 4-bit code of G.721 encoded data of i and
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* returns the resulting linear PCM, A-law or u-law value.
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* return -1 for unknown out_coding value.
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struct g72x_state *state_ptr)
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short sezi, sei, sez, se; /* ACCUM */
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i &= 0x0f; /* mask to get proper bits */
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sezi = predictor_zero(state_ptr);
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sei = sezi + predictor_pole(state_ptr);
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se = sei >> 1; /* se = estimated signal */
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y = step_size(state_ptr); /* dynamic quantizer step size */
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dq = reconstruct(i & 0x08, _dqlntab[i], y); /* quantized diff. */
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sr = (dq < 0) ? (se - (dq & 0x3FFF)) : se + dq; /* reconst. signal */
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dqsez = sr - se + sez; /* pole prediction diff. */
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update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);
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switch (out_coding) {
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case AUDIO_ENCODING_ALAW:
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return (tandem_adjust_alaw(sr, se, y, i, 8, qtab_721));
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case AUDIO_ENCODING_ULAW:
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return (tandem_adjust_ulaw(sr, se, y, i, 8, qtab_721));
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case AUDIO_ENCODING_LINEAR:
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return (sr << 2); /* sr was 14-bit dynamic range */