LIV2/WinUAE
1
0
Fork 0
mirror of https://github.com/LIV2/WinUAE.git synced 2025-12-06 00:12:52 +00:00
Code Issues Packages Projects Releases Wiki Activity
WinUAE/archivers/mp2/kjmp2.cpp
Toni Wilen 189c83566c Warning fixes.
2022-04-29 21:17:21 +03:00

526 lines
22 KiB
C++
Raw Blame History

/******************************************************************************
** kjmp2 -- a minimal MPEG-1/2 Audio Layer II decoder library **
** version 1.1 **
*******************************************************************************
** Copyright (C) 2006-2013 Martin J. Fiedler <martin.fiedler@gmx.net> **
** **
** This software is provided 'as-is', without any express or implied **
** warranty. In no event will the authors be held liable for any damages **
** arising from the use of this software. **
** **
** Permission is granted to anyone to use this software for any purpose, **
** including commercial applications, and to alter it and redistribute it **
** freely, subject to the following restrictions: **
** 1. The origin of this software must not be misrepresented; you must not **
** claim that you wrote the original software. If you use this software **
** in a product, an acknowledgment in the product documentation would **
** be appreciated but is not required. **
** 2. Altered source versions must be plainly marked as such, and must not **
** be misrepresented as being the original software. **
** 3. This notice may not be removed or altered from any source **
** distribution. **
******************************************************************************/
#include <math.h>
#include "kjmp2.h"
#ifdef _MSC_VER
#define FASTCALL __fastcall
#else
#define FASTCALL
#endif
////////////////////////////////////////////////////////////////////////////////
// TABLES AND CONSTANTS //
////////////////////////////////////////////////////////////////////////////////
// mode constants
#define STEREO 0
#define JOINT_STEREO 1
#define DUAL_CHANNEL 2
#define MONO 3
// sample rate table
static const unsigned short sample_rates[8] = {
44100, 48000, 32000, 0, // MPEG-1
22050, 24000, 16000, 0 // MPEG-2
};
// bitrate table
static const short bitrates[28] = {
32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, // MPEG-1
8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160 // MPEG-2
};
// scale factor base values (24-bit fixed-point)
static const int scf_base[3] = { 0x02000000, 0x01965FEA, 0x01428A30 };
// synthesis window
static const int D[512] = {
0x00000, 0x00000, 0x00000, 0x00000, 0x00000, 0x00000, 0x00000,-0x00001,
-0x00001,-0x00001,-0x00001,-0x00002,-0x00002,-0x00003,-0x00003,-0x00004,
-0x00004,-0x00005,-0x00006,-0x00006,-0x00007,-0x00008,-0x00009,-0x0000A,
-0x0000C,-0x0000D,-0x0000F,-0x00010,-0x00012,-0x00014,-0x00017,-0x00019,
-0x0001C,-0x0001E,-0x00022,-0x00025,-0x00028,-0x0002C,-0x00030,-0x00034,
-0x00039,-0x0003E,-0x00043,-0x00048,-0x0004E,-0x00054,-0x0005A,-0x00060,
-0x00067,-0x0006E,-0x00074,-0x0007C,-0x00083,-0x0008A,-0x00092,-0x00099,
-0x000A0,-0x000A8,-0x000AF,-0x000B6,-0x000BD,-0x000C3,-0x000C9,-0x000CF,
0x000D5, 0x000DA, 0x000DE, 0x000E1, 0x000E3, 0x000E4, 0x000E4, 0x000E3,
0x000E0, 0x000DD, 0x000D7, 0x000D0, 0x000C8, 0x000BD, 0x000B1, 0x000A3,
0x00092, 0x0007F, 0x0006A, 0x00053, 0x00039, 0x0001D,-0x00001,-0x00023,
-0x00047,-0x0006E,-0x00098,-0x000C4,-0x000F3,-0x00125,-0x0015A,-0x00190,
-0x001CA,-0x00206,-0x00244,-0x00284,-0x002C6,-0x0030A,-0x0034F,-0x00396,
-0x003DE,-0x00427,-0x00470,-0x004B9,-0x00502,-0x0054B,-0x00593,-0x005D9,
-0x0061E,-0x00661,-0x006A1,-0x006DE,-0x00718,-0x0074D,-0x0077E,-0x007A9,
-0x007D0,-0x007EF,-0x00808,-0x0081A,-0x00824,-0x00826,-0x0081F,-0x0080E,
0x007F5, 0x007D0, 0x007A0, 0x00765, 0x0071E, 0x006CB, 0x0066C, 0x005FF,
0x00586, 0x00500, 0x0046B, 0x003CA, 0x0031A, 0x0025D, 0x00192, 0x000B9,
-0x0002C,-0x0011F,-0x00220,-0x0032D,-0x00446,-0x0056B,-0x0069B,-0x007D5,
-0x00919,-0x00A66,-0x00BBB,-0x00D16,-0x00E78,-0x00FDE,-0x01148,-0x012B3,
-0x01420,-0x0158C,-0x016F6,-0x0185C,-0x019BC,-0x01B16,-0x01C66,-0x01DAC,
-0x01EE5,-0x02010,-0x0212A,-0x02232,-0x02325,-0x02402,-0x024C7,-0x02570,
-0x025FE,-0x0266D,-0x026BB,-0x026E6,-0x026ED,-0x026CE,-0x02686,-0x02615,
-0x02577,-0x024AC,-0x023B2,-0x02287,-0x0212B,-0x01F9B,-0x01DD7,-0x01BDD,
0x019AE, 0x01747, 0x014A8, 0x011D1, 0x00EC0, 0x00B77, 0x007F5, 0x0043A,
0x00046,-0x003E5,-0x00849,-0x00CE3,-0x011B4,-0x016B9,-0x01BF1,-0x0215B,
-0x026F6,-0x02CBE,-0x032B3,-0x038D3,-0x03F1A,-0x04586,-0x04C15,-0x052C4,
-0x05990,-0x06075,-0x06771,-0x06E80,-0x0759F,-0x07CCA,-0x083FE,-0x08B37,
-0x09270,-0x099A7,-0x0A0D7,-0x0A7FD,-0x0AF14,-0x0B618,-0x0BD05,-0x0C3D8,
-0x0CA8C,-0x0D11D,-0x0D789,-0x0DDC9,-0x0E3DC,-0x0E9BD,-0x0EF68,-0x0F4DB,
-0x0FA12,-0x0FF09,-0x103BD,-0x1082C,-0x10C53,-0x1102E,-0x113BD,-0x116FB,
-0x119E8,-0x11C82,-0x11EC6,-0x120B3,-0x12248,-0x12385,-0x12467,-0x124EF,
0x1251E, 0x124F0, 0x12468, 0x12386, 0x12249, 0x120B4, 0x11EC7, 0x11C83,
0x119E9, 0x116FC, 0x113BE, 0x1102F, 0x10C54, 0x1082D, 0x103BE, 0x0FF0A,
0x0FA13, 0x0F4DC, 0x0EF69, 0x0E9BE, 0x0E3DD, 0x0DDCA, 0x0D78A, 0x0D11E,
0x0CA8D, 0x0C3D9, 0x0BD06, 0x0B619, 0x0AF15, 0x0A7FE, 0x0A0D8, 0x099A8,
0x09271, 0x08B38, 0x083FF, 0x07CCB, 0x075A0, 0x06E81, 0x06772, 0x06076,
0x05991, 0x052C5, 0x04C16, 0x04587, 0x03F1B, 0x038D4, 0x032B4, 0x02CBF,
0x026F7, 0x0215C, 0x01BF2, 0x016BA, 0x011B5, 0x00CE4, 0x0084A, 0x003E6,
-0x00045,-0x00439,-0x007F4,-0x00B76,-0x00EBF,-0x011D0,-0x014A7,-0x01746,
0x019AE, 0x01BDE, 0x01DD8, 0x01F9C, 0x0212C, 0x02288, 0x023B3, 0x024AD,
0x02578, 0x02616, 0x02687, 0x026CF, 0x026EE, 0x026E7, 0x026BC, 0x0266E,
0x025FF, 0x02571, 0x024C8, 0x02403, 0x02326, 0x02233, 0x0212B, 0x02011,
0x01EE6, 0x01DAD, 0x01C67, 0x01B17, 0x019BD, 0x0185D, 0x016F7, 0x0158D,
0x01421, 0x012B4, 0x01149, 0x00FDF, 0x00E79, 0x00D17, 0x00BBC, 0x00A67,
0x0091A, 0x007D6, 0x0069C, 0x0056C, 0x00447, 0x0032E, 0x00221, 0x00120,
0x0002D,-0x000B8,-0x00191,-0x0025C,-0x00319,-0x003C9,-0x0046A,-0x004FF,
-0x00585,-0x005FE,-0x0066B,-0x006CA,-0x0071D,-0x00764,-0x0079F,-0x007CF,
0x007F5, 0x0080F, 0x00820, 0x00827, 0x00825, 0x0081B, 0x00809, 0x007F0,
0x007D1, 0x007AA, 0x0077F, 0x0074E, 0x00719, 0x006DF, 0x006A2, 0x00662,
0x0061F, 0x005DA, 0x00594, 0x0054C, 0x00503, 0x004BA, 0x00471, 0x00428,
0x003DF, 0x00397, 0x00350, 0x0030B, 0x002C7, 0x00285, 0x00245, 0x00207,
0x001CB, 0x00191, 0x0015B, 0x00126, 0x000F4, 0x000C5, 0x00099, 0x0006F,
0x00048, 0x00024, 0x00002,-0x0001C,-0x00038,-0x00052,-0x00069,-0x0007E,
-0x00091,-0x000A2,-0x000B0,-0x000BC,-0x000C7,-0x000CF,-0x000D6,-0x000DC,
-0x000DF,-0x000E2,-0x000E3,-0x000E3,-0x000E2,-0x000E0,-0x000DD,-0x000D9,
0x000D5, 0x000D0, 0x000CA, 0x000C4, 0x000BE, 0x000B7, 0x000B0, 0x000A9,
0x000A1, 0x0009A, 0x00093, 0x0008B, 0x00084, 0x0007D, 0x00075, 0x0006F,
0x00068, 0x00061, 0x0005B, 0x00055, 0x0004F, 0x00049, 0x00044, 0x0003F,
0x0003A, 0x00035, 0x00031, 0x0002D, 0x00029, 0x00026, 0x00023, 0x0001F,
0x0001D, 0x0001A, 0x00018, 0x00015, 0x00013, 0x00011, 0x00010, 0x0000E,
0x0000D, 0x0000B, 0x0000A, 0x00009, 0x00008, 0x00007, 0x00007, 0x00006,
0x00005, 0x00005, 0x00004, 0x00004, 0x00003, 0x00003, 0x00002, 0x00002,
0x00002, 0x00002, 0x00001, 0x00001, 0x00001, 0x00001, 0x00001, 0x00001
};
///////////// Table 3-B.2: Possible quantization per subband ///////////////////
// quantizer lookup, step 1: bitrate classes
static const char quant_lut_step1[2][16] = {
// 32, 48, 56, 64, 80, 96,112,128,160,192,224,256,320,384 <- bitrate
{ 0, 0, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2 }, // mono
// 16, 24, 28, 32, 40, 48, 56, 64, 80, 96,112,128,160,192 <- BR / chan
{ 0, 0, 0, 0, 0, 0, 1, 1, 1, 2, 2, 2, 2, 2 } // stereo
};
// quantizer lookup, step 2: bitrate class, sample rate -> B2 table idx, sblimit
#define QUANT_TAB_A (27 | 64) // Table 3-B.2a: high-rate, sblimit = 27
#define QUANT_TAB_B (30 | 64) // Table 3-B.2b: high-rate, sblimit = 30
#define QUANT_TAB_C 8 // Table 3-B.2c: low-rate, sblimit = 8
#define QUANT_TAB_D 12 // Table 3-B.2d: low-rate, sblimit = 12
static const char quant_lut_step2[3][4] = {
// 44.1 kHz, 48 kHz, 32 kHz
{ QUANT_TAB_C, QUANT_TAB_C, QUANT_TAB_D }, // 32 - 48 kbit/sec/ch
{ QUANT_TAB_A, QUANT_TAB_A, QUANT_TAB_A }, // 56 - 80 kbit/sec/ch
{ QUANT_TAB_B, QUANT_TAB_A, QUANT_TAB_B }, // 96+ kbit/sec/ch
};
// quantizer lookup, step 3: B2 table, subband -> nbal, row index
// (upper 4 bits: nbal, lower 4 bits: row index)
static const char quant_lut_step3[3][32] = {
// low-rate table (3-B.2c and 3-B.2d)
{ 0x44,0x44, // SB 0 - 1
0x34,0x34,0x34,0x34,0x34,0x34,0x34,0x34,0x34,0x34 // SB 2 - 12
},
// high-rate table (3-B.2a and 3-B.2b)
{ 0x43,0x43,0x43, // SB 0 - 2
0x42,0x42,0x42,0x42,0x42,0x42,0x42,0x42, // SB 3 - 10
0x31,0x31,0x31,0x31,0x31,0x31,0x31,0x31,0x31,0x31,0x31,0x31, // SB 11 - 22
0x20,0x20,0x20,0x20,0x20,0x20,0x20 // SB 23 - 29
},
// MPEG-2 LSR table (B.2 in ISO 13818-3)
{ 0x45,0x45,0x45,0x45, // SB 0 - 3
0x34,0x34,0x34,0x34,0x34,0x34,0x34, // SB 4 - 10
0x24,0x24,0x24,0x24,0x24,0x24,0x24,0x24,0x24,0x24, // SB 11 -
0x24,0x24,0x24,0x24,0x24,0x24,0x24,0x24,0x24 // - 29
}
};
// quantizer lookup, step 4: table row, allocation[] value -> quant table index
static const char quant_lut_step4[6][16] = {
{ 0, 1, 2, 17 },
{ 0, 1, 2, 3, 4, 5, 6, 17 },
{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 17 },
{ 0, 1, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 },
{ 0, 1, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17 },
{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 }
};
// quantizer specification structure
struct quantizer_spec {
unsigned short nlevels;
unsigned char grouping;
unsigned char cw_bits;
};
// quantizer table
static const struct quantizer_spec quantizer_table[17] = {
{ 3, 1, 5 }, // 1
{ 5, 1, 7 }, // 2
{ 7, 0, 3 }, // 3
{ 9, 1, 10 }, // 4
{ 15, 0, 4 }, // 5
{ 31, 0, 5 }, // 6
{ 63, 0, 6 }, // 7
{ 127, 0, 7 }, // 8
{ 255, 0, 8 }, // 9
{ 511, 0, 9 }, // 10
{ 1023, 0, 10 }, // 11
{ 2047, 0, 11 }, // 12
{ 4095, 0, 12 }, // 13
{ 8191, 0, 13 }, // 14
{ 16383, 0, 14 }, // 15
{ 32767, 0, 15 }, // 16
{ 65535, 0, 16 } // 17
};
////////////////////////////////////////////////////////////////////////////////
// STATIC VARIABLES AND FUNCTIONS //
////////////////////////////////////////////////////////////////////////////////
#define KJMP2_MAGIC 0x32706D
static int initialized = 0;
static int bit_window;
static int bits_in_window;
static const unsigned char *frame_pos;
#define show_bits(bit_count) (bit_window >> (24 - (bit_count)))
static int FASTCALL get_bits(int bit_count) {
int result = show_bits(bit_count);
bit_window = (bit_window << bit_count) & 0xFFFFFF;
bits_in_window -= bit_count;
while (bits_in_window < 16) {
bit_window |= (*frame_pos++) << (16 - bits_in_window);
bits_in_window += 8;
}
return result;
}
////////////////////////////////////////////////////////////////////////////////
// INITIALIZATION //
////////////////////////////////////////////////////////////////////////////////
static int N[64][32]; // N[i][j] as 8-bit fixed-point
void kjmp2_init(kjmp2_context_t *mp2) {
int i, j;
// check if global initialization is required
if (!initialized) {
int *nptr = &N[0][0];
// compute N[i][j]
for (i = 0; i < 64; ++i)
for (j = 0; j < 32; ++j)
*nptr++ = (int) (256.0 * cos(((16 + i) * ((j << 1) + 1)) * 0.0490873852123405));
initialized = 1;
}
// perform local initialization: clean the context and put the magic in it
for (i = 0; i < 2; ++i)
for (j = 1023; j >= 0; --j)
mp2->V[i][j] = 0;
mp2->Voffs = 0;
mp2->id = KJMP2_MAGIC;
}
int kjmp2_get_sample_rate(const unsigned char *frame) {
if (!frame)
return 0;
if (( frame[0] != 0xFF) // no valid syncword?
|| ((frame[1] & 0xF6) != 0xF4) // no MPEG-1/2 Audio Layer II?
|| ((frame[2] - 0x10) >= 0xE0)) // invalid bitrate?
return 0;
return sample_rates[(((frame[1] & 0x08) >> 1) ^ 4) // MPEG-1/2 switch
+ ((frame[2] >> 2) & 3)]; // actual rate
}
////////////////////////////////////////////////////////////////////////////////
// DECODE HELPER FUNCTIONS //
////////////////////////////////////////////////////////////////////////////////
static const struct quantizer_spec* FASTCALL read_allocation(int sb, int b2_table) {
int table_idx = quant_lut_step3[b2_table][sb];
table_idx = quant_lut_step4[table_idx & 15][get_bits(table_idx >> 4)];
return table_idx ? (&quantizer_table[table_idx - 1]) : 0;
}
static void FASTCALL read_samples(const struct quantizer_spec *q, int scalefactor, int *sample) {
int idx, adj, scale;
int val;
if (!q) {
// no bits allocated for this subband
sample[0] = sample[1] = sample[2] = 0;
return;
}
// resolve scalefactor
if (scalefactor == 63) {
scalefactor = 0;
} else {
adj = scalefactor / 3;
scalefactor = (scf_base[scalefactor % 3] + ((1 << adj) >> 1)) >> adj;
}
// decode samples
adj = q->nlevels;
if (q->grouping) {
// decode grouped samples
val = get_bits(q->cw_bits);
sample[0] = val % adj;
val /= adj;
sample[1] = val % adj;
sample[2] = val / adj;
} else {
// decode direct samples
for(idx = 0; idx < 3; ++idx)
sample[idx] = get_bits(q->cw_bits);
}
// postmultiply samples
scale = 65536 / (adj + 1);
adj = ((adj + 1) >> 1) - 1;
for (idx = 0; idx < 3; ++idx) {
// step 1: renormalization to [-1..1]
val = (adj - sample[idx]) * scale;
// step 2: apply scalefactor
sample[idx] = ( val * (scalefactor >> 12) // upper part
+ ((val * (scalefactor & 4095) + 2048) >> 12)) // lower part
>> 12; // scale adjust
}
}
////////////////////////////////////////////////////////////////////////////////
// FRAME DECODE FUNCTION //
////////////////////////////////////////////////////////////////////////////////
static const struct quantizer_spec *allocation[2][32];
static int scfsi[2][32];
static int scalefactor[2][32][3];
static int sample[2][32][3];
static int U[512];
unsigned long kjmp2_decode_frame(
kjmp2_context_t *mp2,
const unsigned char *frame,
signed short *pcm
) {
unsigned bit_rate_index_minus1;
unsigned sampling_frequency;
unsigned padding_bit;
unsigned mode;
unsigned long frame_size;
int bound, sblimit;
int sb, ch, gr, part, idx, nch, i, j, sum;
int table_idx;
// general sanity check
if (!initialized || !mp2 || (mp2->id != KJMP2_MAGIC) || !frame)
return 0;
// check for valid header: syncword OK, MPEG-Audio Layer 2
if ((frame[0] != 0xFF) || ((frame[1] & 0xF6) != 0xF4))
return 0;
// set up the bitstream reader
bit_window = frame[2] << 16;
bits_in_window = 8;
frame_pos = &frame[3];
// read the rest of the header
bit_rate_index_minus1 = get_bits(4) - 1;
if (bit_rate_index_minus1 > 13)
return 0; // invalid bit rate or 'free format'
sampling_frequency = get_bits(2);
if (sampling_frequency == 3)
return 0;
if ((frame[1] & 0x08) == 0) { // MPEG-2
sampling_frequency += 4;
bit_rate_index_minus1 += 14;
}
padding_bit = get_bits(1);
get_bits(1); // discard private_bit
mode = get_bits(2);
// parse the mode_extension, set up the stereo bound
if (mode == JOINT_STEREO) {
bound = (get_bits(2) + 1) << 2;
} else {
get_bits(2);
bound = (mode == MONO) ? 0 : 32;
}
// discard the last 4 bits of the header and the CRC value, if present
get_bits(4);
if ((frame[1] & 1) == 0)
get_bits(16);
// compute the frame size
frame_size = (144000 * bitrates[bit_rate_index_minus1]
/ sample_rates[sampling_frequency]) + padding_bit;
if (!pcm)
return frame_size; // no decoding
// prepare the quantizer table lookups
if (sampling_frequency & 4) {
// MPEG-2 (LSR)
table_idx = 2;
sblimit = 30;
} else {
// MPEG-1
table_idx = (mode == MONO) ? 0 : 1;
table_idx = quant_lut_step1[table_idx][bit_rate_index_minus1];
table_idx = quant_lut_step2[table_idx][sampling_frequency];
sblimit = table_idx & 63;
table_idx >>= 6;
}
if (bound > sblimit)
bound = sblimit;
// read the allocation information
for (sb = 0; sb < bound; ++sb)
for (ch = 0; ch < 2; ++ch)
allocation[ch][sb] = read_allocation(sb, table_idx);
for (sb = bound; sb < sblimit; ++sb)
allocation[0][sb] = allocation[1][sb] = read_allocation(sb, table_idx);
// read scale factor selector information
nch = (mode == MONO) ? 1 : 2;
for (sb = 0; sb < sblimit; ++sb) {
for (ch = 0; ch < nch; ++ch)
if (allocation[ch][sb])
scfsi[ch][sb] = get_bits(2);
if (mode == MONO)
scfsi[1][sb] = scfsi[0][sb];
}
// read scale factors
for (sb = 0; sb < sblimit; ++sb) {
for (ch = 0; ch < nch; ++ch)
if (allocation[ch][sb]) {
switch (scfsi[ch][sb]) {
case 0: scalefactor[ch][sb][0] = get_bits(6);
scalefactor[ch][sb][1] = get_bits(6);
scalefactor[ch][sb][2] = get_bits(6);
break;
case 1: scalefactor[ch][sb][0] =
scalefactor[ch][sb][1] = get_bits(6);
scalefactor[ch][sb][2] = get_bits(6);
break;
case 2: scalefactor[ch][sb][0] =
scalefactor[ch][sb][1] =
scalefactor[ch][sb][2] = get_bits(6);
break;
case 3: scalefactor[ch][sb][0] = get_bits(6);
scalefactor[ch][sb][1] =
scalefactor[ch][sb][2] = get_bits(6);
break;
}
}
if (mode == MONO)
for (part = 0; part < 3; ++part)
scalefactor[1][sb][part] = scalefactor[0][sb][part];
}
// coefficient input and reconstruction
for (part = 0; part < 3; ++part)
for (gr = 0; gr < 4; ++gr) {
// read the samples
for (sb = 0; sb < bound; ++sb)
for (ch = 0; ch < 2; ++ch)
read_samples(allocation[ch][sb], scalefactor[ch][sb][part], &sample[ch][sb][0]);
for (sb = bound; sb < sblimit; ++sb) {
read_samples(allocation[0][sb], scalefactor[0][sb][part], &sample[0][sb][0]);
for (idx = 0; idx < 3; ++idx)
sample[1][sb][idx] = sample[0][sb][idx];
}
for (ch = 0; ch < 2; ++ch)
for (sb = sblimit; sb < 32; ++sb)
for (idx = 0; idx < 3; ++idx)
sample[ch][sb][idx] = 0;
// synthesis loop
for (idx = 0; idx < 3; ++idx) {
// shifting step
mp2->Voffs = table_idx = (mp2->Voffs - 64) & 1023;
for (ch = 0; ch < 2; ++ch) {
// matrixing
for (i = 0; i < 64; ++i) {
sum = 0;
for (j = 0; j < 32; ++j)
sum += N[i][j] * sample[ch][j][idx]; // 8b*15b=23b
// intermediate value is 28 bit (23 + 5), clamp to 14b
mp2->V[ch][table_idx + i] = (sum + 8192) >> 14;
}
// construction of U
for (i = 0; i < 8; ++i)
for (j = 0; j < 32; ++j) {
U[(i << 6) + j] = mp2->V[ch][(table_idx + (i << 7) + j ) & 1023];
U[(i << 6) + j + 32] = mp2->V[ch][(table_idx + (i << 7) + j + 96) & 1023];
}
// apply window
for (i = 0; i < 512; ++i)
U[i] = (U[i] * D[i] + 32) >> 6;
// output samples
for (j = 0; j < 32; ++j) {
sum = 0;
for (i = 0; i < 16; ++i)
sum -= U[(i << 5) + j];
sum = (sum + 8) >> 4;
if (sum < -32768) sum = -32768;
if (sum > 32767) sum = 32767;
pcm[(idx << 6) | (j << 1) | ch] = (signed short) sum;
}
} // end of synthesis channel loop
} // end of synthesis sub-block loop
// adjust PCM output pointer: decoded 3 * 32 = 96 stereo samples
pcm += 192;
} // decoding of the granule finished
return frame_size;
}
Reference in New Issue View Git Blame Copy Permalink