rockbox/lib/rbcodec/codecs/demac/libdemac/entropy.c

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/*
libdemac - A Monkey's Audio decoder
$Id$
Copyright (C) Dave Chapman 2007
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110, USA
*/
#include <inttypes.h>
#include <string.h>
#include "parser.h"
#include "entropy.h"
#include "demac_config.h"
#define MODEL_ELEMENTS 64
/*
The following counts arrays for use with the range decoder are
hard-coded in the Monkey's Audio decoder.
*/
static const int counts_3970[65] ICONST_ATTR_DEMAC =
{
0,14824,28224,39348,47855,53994,58171,60926,
62682,63786,64463,64878,65126,65276,65365,65419,
65450,65469,65480,65487,65491,65493,65494,65495,
65496,65497,65498,65499,65500,65501,65502,65503,
65504,65505,65506,65507,65508,65509,65510,65511,
65512,65513,65514,65515,65516,65517,65518,65519,
65520,65521,65522,65523,65524,65525,65526,65527,
65528,65529,65530,65531,65532,65533,65534,65535,
65536
};
/* counts_diff_3970[i] = counts_3970[i+1] - counts_3970[i] */
static const int counts_diff_3970[64] ICONST_ATTR_DEMAC =
{
14824,13400,11124,8507,6139,4177,2755,1756,
1104,677,415,248,150,89,54,31,
19,11,7,4,2,1,1,1,
1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1
};
static const int counts_3980[65] ICONST_ATTR_DEMAC =
{
0,19578,36160,48417,56323,60899,63265,64435,
64971,65232,65351,65416,65447,65466,65476,65482,
65485,65488,65490,65491,65492,65493,65494,65495,
65496,65497,65498,65499,65500,65501,65502,65503,
65504,65505,65506,65507,65508,65509,65510,65511,
65512,65513,65514,65515,65516,65517,65518,65519,
65520,65521,65522,65523,65524,65525,65526,65527,
65528,65529,65530,65531,65532,65533,65534,65535,
65536
};
/* counts_diff_3980[i] = counts_3980[i+1] - counts_3980[i] */
static const int counts_diff_3980[64] ICONST_ATTR_DEMAC =
{
19578,16582,12257,7906,4576,2366,1170,536,
261,119,65,31,19,10,6,3,
3,2,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1
};
/*
Range decoder adapted from rangecod.c included in:
http://www.compressconsult.com/rangecoder/rngcod13.zip
rangecod.c range encoding
(c) Michael Schindler
1997, 1998, 1999, 2000
http://www.compressconsult.com/
michael@compressconsult.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
The encoding functions were removed, and functions turned into "static
inline" functions. Some minor cosmetic changes were made (e.g. turning
pre-processor symbols into upper-case, removing the rc parameter from
each function (and the RNGC macro)).
*/
/* BITSTREAM READING FUNCTIONS */
/* We deal with the input data one byte at a time - to ensure
functionality on CPUs of any endianness regardless of any requirements
for aligned reads.
*/
static unsigned char* bytebuffer IBSS_ATTR_DEMAC;
static int bytebufferoffset IBSS_ATTR_DEMAC;
static inline void skip_byte(void)
{
bytebufferoffset--;
bytebuffer += bytebufferoffset & 4;
bytebufferoffset &= 3;
}
static inline int read_byte(void)
{
int ch = bytebuffer[bytebufferoffset];
skip_byte();
return ch;
}
/* RANGE DECODING FUNCTIONS */
/* SIZE OF RANGE ENCODING CODE VALUES. */
#define CODE_BITS 32
#define TOP_VALUE ((unsigned int)1 << (CODE_BITS-1))
#define SHIFT_BITS (CODE_BITS - 9)
#define EXTRA_BITS ((CODE_BITS-2) % 8 + 1)
#define BOTTOM_VALUE (TOP_VALUE >> 8)
struct rangecoder_t
{
uint32_t low; /* low end of interval */
uint32_t range; /* length of interval */
uint32_t help; /* bytes_to_follow resp. intermediate value */
unsigned int buffer; /* buffer for input/output */
};
static struct rangecoder_t rc IBSS_ATTR_DEMAC;
/* Start the decoder */
static inline void range_start_decoding(void)
{
rc.buffer = read_byte();
rc.low = rc.buffer >> (8 - EXTRA_BITS);
rc.range = (uint32_t) 1 << EXTRA_BITS;
}
static inline void range_dec_normalize(void)
{
while (rc.range <= BOTTOM_VALUE)
{
rc.buffer = (rc.buffer << 8) | read_byte();
rc.low = (rc.low << 8) | ((rc.buffer >> 1) & 0xff);
rc.range <<= 8;
}
}
/* Calculate culmulative frequency for next symbol. Does NO update!*/
/* tot_f is the total frequency */
/* or: totf is (code_value)1<<shift */
/* returns the culmulative frequency */
static inline int range_decode_culfreq(int tot_f)
{
range_dec_normalize();
rc.help = UDIV32(rc.range, tot_f);
return UDIV32(rc.low, rc.help);
}
static inline int range_decode_culshift(int shift)
{
range_dec_normalize();
rc.help = rc.range >> shift;
return UDIV32(rc.low, rc.help);
}
/* Update decoding state */
/* sy_f is the interval length (frequency of the symbol) */
/* lt_f is the lower end (frequency sum of < symbols) */
static inline void range_decode_update(int sy_f, int lt_f)
{
rc.low -= rc.help * lt_f;
rc.range = rc.help * sy_f;
}
/* Decode a byte/short without modelling */
static inline unsigned char decode_byte(void)
{ int tmp = range_decode_culshift(8);
range_decode_update( 1,tmp);
return tmp;
}
static inline unsigned short range_decode_short(void)
{ int tmp = range_decode_culshift(16);
range_decode_update( 1,tmp);
return tmp;
}
/* Decode n bits (n <= 16) without modelling - based on range_decode_short */
static inline int range_decode_bits(int n)
{ int tmp = range_decode_culshift(n);
range_decode_update( 1,tmp);
return tmp;
}
/* Finish decoding */
static inline void range_done_decoding(void)
{ range_dec_normalize(); /* normalize to use up all bytes */
}
/*
range_get_symbol_* functions based on main decoding loop in simple_d.c from
http://www.compressconsult.com/rangecoder/rngcod13.zip
(c) Michael Schindler
*/
static inline int range_get_symbol_3980(void)
{
int symbol, cf;
cf = range_decode_culshift(16);
/* figure out the symbol inefficiently; a binary search would be much better */
for (symbol = 0; counts_3980[symbol+1] <= cf; symbol++);
range_decode_update(counts_diff_3980[symbol],counts_3980[symbol]);
return symbol;
}
static inline int range_get_symbol_3970(void)
{
int symbol, cf;
cf = range_decode_culshift(16);
/* figure out the symbol inefficiently; a binary search would be much better */
for (symbol = 0; counts_3970[symbol+1] <= cf; symbol++);
range_decode_update(counts_diff_3970[symbol],counts_3970[symbol]);
return symbol;
}
/* MAIN DECODING FUNCTIONS */
struct rice_t
{
uint32_t k;
uint32_t ksum;
};
static struct rice_t riceX IBSS_ATTR_DEMAC;
static struct rice_t riceY IBSS_ATTR_DEMAC;
static inline void update_rice(struct rice_t* rice, int x)
{
rice->ksum += ((x + 1) / 2) - ((rice->ksum + 16) >> 5);
if (UNLIKELY(rice->k == 0)) {
rice->k = 1;
} else {
uint32_t lim = 1 << (rice->k + 4);
if (UNLIKELY(rice->ksum < lim)) {
rice->k--;
} else if (UNLIKELY(rice->ksum >= 2 * lim)) {
rice->k++;
}
}
}
static inline int entropy_decode3980(struct rice_t* rice)
{
int base, x, pivot, overflow;
pivot = rice->ksum >> 5;
if (UNLIKELY(pivot == 0))
pivot=1;
overflow = range_get_symbol_3980();
if (UNLIKELY(overflow == (MODEL_ELEMENTS-1))) {
overflow = range_decode_short() << 16;
overflow |= range_decode_short();
}
if (pivot >= 0x10000) {
/* Codepath for 24-bit streams */
int nbits, lo_bits, base_hi, base_lo;
/* Count the number of bits in pivot */
nbits = 17; /* We know there must be at least 17 bits */
while ((pivot >> nbits) > 0) { nbits++; }
/* base_lo is the low (nbits-16) bits of base
base_hi is the high 16 bits of base
*/
lo_bits = (nbits - 16);
base_hi = range_decode_culfreq((pivot >> lo_bits) + 1);
range_decode_update(1, base_hi);
base_lo = range_decode_culshift(lo_bits);
range_decode_update(1, base_lo);
base = (base_hi << lo_bits) + base_lo;
} else {
/* Codepath for 16-bit streams */
base = range_decode_culfreq(pivot);
range_decode_update(1, base);
}
x = base + (overflow * pivot);
update_rice(rice, x);
/* Convert to signed */
if (x & 1)
return (x >> 1) + 1;
else
return -(x >> 1);
}
static inline int entropy_decode3970(struct rice_t* rice)
{
int x, tmpk;
int overflow = range_get_symbol_3970();
if (UNLIKELY(overflow == (MODEL_ELEMENTS - 1))) {
tmpk = range_decode_bits(5);
overflow = 0;
} else {
tmpk = (rice->k < 1) ? 0 : rice->k - 1;
}
if (tmpk <= 16) {
x = range_decode_bits(tmpk);
} else {
x = range_decode_short();
x |= (range_decode_bits(tmpk - 16) << 16);
}
x += (overflow << tmpk);
update_rice(rice, x);
/* Convert to signed */
if (x & 1)
return (x >> 1) + 1;
else
return -(x >> 1);
}
void init_entropy_decoder(struct ape_ctx_t* ape_ctx,
unsigned char* inbuffer, int* firstbyte,
int* bytesconsumed)
{
bytebuffer = inbuffer;
bytebufferoffset = *firstbyte;
/* Read the CRC */
ape_ctx->CRC = read_byte();
ape_ctx->CRC = (ape_ctx->CRC << 8) | read_byte();
ape_ctx->CRC = (ape_ctx->CRC << 8) | read_byte();
ape_ctx->CRC = (ape_ctx->CRC << 8) | read_byte();
/* Read the frame flags if they exist */
ape_ctx->frameflags = 0;
if ((ape_ctx->fileversion > 3820) && (ape_ctx->CRC & 0x80000000)) {
ape_ctx->CRC &= ~0x80000000;
ape_ctx->frameflags = read_byte();
ape_ctx->frameflags = (ape_ctx->frameflags << 8) | read_byte();
ape_ctx->frameflags = (ape_ctx->frameflags << 8) | read_byte();
ape_ctx->frameflags = (ape_ctx->frameflags << 8) | read_byte();
}
/* Keep a count of the blocks decoded in this frame */
ape_ctx->blocksdecoded = 0;
/* Initialise the rice structs */
riceX.k = 10;
riceX.ksum = (1 << riceX.k) * 16;
riceY.k = 10;
riceY.ksum = (1 << riceY.k) * 16;
/* The first 8 bits of input are ignored. */
skip_byte();
range_start_decoding();
/* Return the new state of the buffer */
*bytesconsumed = (intptr_t)bytebuffer - (intptr_t)inbuffer;
*firstbyte = bytebufferoffset;
}
void ICODE_ATTR_DEMAC entropy_decode(struct ape_ctx_t* ape_ctx,
unsigned char* inbuffer, int* firstbyte,
int* bytesconsumed,
int32_t* decoded0, int32_t* decoded1,
int blockstodecode)
{
bytebuffer = inbuffer;
bytebufferoffset = *firstbyte;
ape_ctx->blocksdecoded += blockstodecode;
if ((ape_ctx->frameflags & APE_FRAMECODE_LEFT_SILENCE)
&& ((ape_ctx->frameflags & APE_FRAMECODE_RIGHT_SILENCE)
|| (decoded1 == NULL))) {
/* We are pure silence, just memset the output buffer. */
memset(decoded0, 0, blockstodecode * sizeof(int32_t));
if (decoded1 != NULL)
memset(decoded1, 0, blockstodecode * sizeof(int32_t));
} else {
if (ape_ctx->fileversion > 3970) {
while (LIKELY(blockstodecode--)) {
*(decoded0++) = entropy_decode3980(&riceY);
if (decoded1 != NULL)
*(decoded1++) = entropy_decode3980(&riceX);
}
} else {
while (LIKELY(blockstodecode--)) {
*(decoded0++) = entropy_decode3970(&riceY);
if (decoded1 != NULL)
*(decoded1++) = entropy_decode3970(&riceX);
}
}
}
if (ape_ctx->blocksdecoded == ape_ctx->currentframeblocks)
{
range_done_decoding();
}
/* Return the new state of the buffer */
*bytesconsumed = bytebuffer - inbuffer;
*firstbyte = bytebufferoffset;
}