alac.c

alac decoder,内容详细

/*
 * ALAC (Apple Lossless Audio Codec) decoder
 * Copyright (c) 2005 David Hammerton
 * All rights reserved.
 *
 * This is the actual decoder.
 *
 * http://crazney.net/programs/itunes/alac.html
 * 
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 */


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

#include "decomp.h"

#define _Swap32(v) do { \
                   v = (((v) & 0x000000FF) << 0x18) | \
                       (((v) & 0x0000FF00) << 0x08) | \
                       (((v) & 0x00FF0000) >> 0x08) | \
                       (((v) & 0xFF000000) >> 0x18); } while(0)

#define _Swap16(v) do { \
                   v = (((v) & 0x00FF) << 0x08) | \
                       (((v) & 0xFF00) >> 0x08); } while (0)


extern int host_bigendian;

struct alac_file
{
    unsigned char *input_buffer;
    int input_buffer_bitaccumulator; /* used so we can do arbitary
                                        bit reads */

    int samplesize;
    int numchannels;
    int bytespersample;


    /* buffers */
    int32_t *predicterror_buffer_a;
    int32_t *predicterror_buffer_b;

    int32_t *outputsamples_buffer_a;
    int32_t *outputsamples_buffer_b;


  /* stuff from setinfo */
  uint32_t setinfo_max_samples_per_frame; /* 0x1000 = 4096 */    /* max samples per frame? */
  uint8_t setinfo_7a; /* 0x00 */
  uint8_t setinfo_sample_size; /* 0x10 */
  uint8_t setinfo_rice_historymult; /* 0x28 */
  uint8_t setinfo_rice_initialhistory; /* 0x0a */
  uint8_t setinfo_rice_kmodifier; /* 0x0e */
  uint8_t setinfo_7f; /* 0x02 */
  uint16_t setinfo_80; /* 0x00ff */
  uint32_t setinfo_82; /* 0x000020e7 */ /* max sample size?? */
  uint32_t setinfo_86; /* 0x00069fe4 */ /* bit rate (avarge)?? */
  uint32_t setinfo_8a_rate; /* 0x0000ac44 */
  /* end setinfo stuff */

};


static void allocate_buffers(alac_file *alac)
{
    alac->predicterror_buffer_a = malloc(alac->setinfo_max_samples_per_frame * 4);
    alac->predicterror_buffer_b = malloc(alac->setinfo_max_samples_per_frame * 4);

    alac->outputsamples_buffer_a = malloc(alac->setinfo_max_samples_per_frame * 4);
    alac->outputsamples_buffer_b = malloc(alac->setinfo_max_samples_per_frame * 4);
}

void alac_set_info(alac_file *alac, char *inputbuffer)
{
  char *ptr = inputbuffer;
  ptr += 4; /* size */
  ptr += 4; /* frma */
  ptr += 4; /* alac */
  ptr += 4; /* size */
  ptr += 4; /* alac */

  ptr += 4; /* 0 ? */

  alac->setinfo_max_samples_per_frame = *(uint32_t*)ptr; /* buffer size / 2 ? */
  if (!host_bigendian)
      _Swap32(alac->setinfo_max_samples_per_frame);
  ptr += 4;
  alac->setinfo_7a = *(uint8_t*)ptr;
  ptr += 1;
  alac->setinfo_sample_size = *(uint8_t*)ptr;
  ptr += 1;
  alac->setinfo_rice_historymult = *(uint8_t*)ptr;
  ptr += 1;
  alac->setinfo_rice_initialhistory = *(uint8_t*)ptr;
  ptr += 1;
  alac->setinfo_rice_kmodifier = *(uint8_t*)ptr;
  ptr += 1;
  alac->setinfo_7f = *(uint8_t*)ptr;
  ptr += 1;
  alac->setinfo_80 = *(uint16_t*)ptr;
  if (!host_bigendian)
      _Swap16(alac->setinfo_80);
  ptr += 2;
  alac->setinfo_82 = *(uint32_t*)ptr;
  if (!host_bigendian)
      _Swap32(alac->setinfo_82);
  ptr += 4;
  alac->setinfo_86 = *(uint32_t*)ptr;
  if (!host_bigendian)
      _Swap32(alac->setinfo_86);
  ptr += 4;
  alac->setinfo_8a_rate = *(uint32_t*)ptr;
  if (!host_bigendian)
      _Swap32(alac->setinfo_8a_rate);
  ptr += 4;

  allocate_buffers(alac);

}

/* stream reading */

/* supports reading 1 to 16 bits, in big endian format */
static uint32_t readbits_16(alac_file *alac, int bits)
{
    uint32_t result;
    int new_accumulator;

    result = (alac->input_buffer[0] << 16) |
             (alac->input_buffer[1] << 8) |
             (alac->input_buffer[2]);

    /* shift left by the number of bits we've already read,
     * so that the top 'n' bits of the 24 bits we read will
     * be the return bits */
    result = result << alac->input_buffer_bitaccumulator;

    result = result & 0x00ffffff;

    /* and then only want the top 'n' bits from that, where
     * n is 'bits' */
    result = result >> (24 - bits);

    new_accumulator = (alac->input_buffer_bitaccumulator + bits);

    /* increase the buffer pointer if we've read over n bytes. */
    alac->input_buffer += (new_accumulator >> 3);

    /* and the remainder goes back into the bit accumulator */
    alac->input_buffer_bitaccumulator = (new_accumulator & 7);

    return result;
}

/* supports reading 1 to 32 bits, in big endian format */
static uint32_t readbits(alac_file *alac, int bits)
{
    int32_t result = 0;

    if (bits > 16)
    {
        bits -= 16;
        result = readbits_16(alac, 16) << bits;
    }

    result |= readbits_16(alac, bits);

    return result;
}

/* reads a single bit */
static int readbit(alac_file *alac)
{
    int result;
    int new_accumulator;

    result = alac->input_buffer[0];

    result = result << alac->input_buffer_bitaccumulator;

    result = result >> 7 & 1;

    new_accumulator = (alac->input_buffer_bitaccumulator + 1);

    alac->input_buffer += (new_accumulator / 8);

    alac->input_buffer_bitaccumulator = (new_accumulator % 8);

    return result;
}

static void unreadbits(alac_file *alac, int bits)
{
    int new_accumulator = (alac->input_buffer_bitaccumulator - bits);

    alac->input_buffer += (new_accumulator >> 3);

    alac->input_buffer_bitaccumulator = (new_accumulator & 7);
    if (alac->input_buffer_bitaccumulator < 0)
        alac->input_buffer_bitaccumulator *= -1;
}

/* various implementations of count_leading_zero:
 * the first one is the original one, the simplest and most
 * obvious for what it's doing. never use this.
 * then there are the asm ones. fill in as necessary
 * and finally an unrolled and optimised c version
 * to fall back to
 */
#if 0
/* hideously inefficient. could use a bitmask search,
 * alternatively bsr on x86,
 */
static int count_leading_zeros(int32_t input)
{
    int i = 0;
    while (!(0x80000000 & input) && i < 32)
    {
        i++;
        input = input << 1;
    }
    return i;
}
#elif defined(__GNUC__) && (defined(_X86) || defined(__i386) || defined(i386))
/* for some reason the unrolled version (below) is
 * actually faster than this. yay intel!
 */
static int count_leading_zeros(int input)
{
    int output = 0;
    if (!input) return 32;
    asm("bsr %1, %0\n"
        : "=r" (output)
        : "r" (input));
    return (0x1f - output);
}
#elif defined(_MSC_VER) && defined(_M_IX86)
static int count_leading_zeros(int input)
{
    int output = 0;
    if (!input) return 32;
    __asm
    {
        mov eax, input;
        mov edx, 0x1f;
        bsr ecx, eax;
        sub edx, ecx;
        mov output, edx;
    }
    return output;
}
#else
#warning using generic count leading zeroes. You may wish to write one for your CPU / compiler
static int count_leading_zeros(int input)
{
    int output = 0;
    int curbyte = 0;

    curbyte = input >> 24;
    if (curbyte) goto found;
    output += 8;

    curbyte = input >> 16;
    if (curbyte & 0xff) goto found;
    output += 8;

    curbyte = input >> 8;
    if (curbyte & 0xff) goto found;
    output += 8;

    curbyte = input;
    if (curbyte & 0xff) goto found;
    output += 8;

    return output;

found:
    if (!(curbyte & 0xf0))
    {
        output += 4;
    }
    else
        curbyte >>= 4;

    if (curbyte & 0x8)
        return output;
    if (curbyte & 0x4)
        return output + 1;
    if (curbyte & 0x2)
        return output + 2;
    if (curbyte & 0x1)
        return output + 3;

    /* shouldn't get here: */
    return output + 4;
}
#endif

void basterdised_rice_decompress(alac_file *alac,
                                 int32_t *output_buffer,
                                 int output_size,
                                 int readsamplesize, /* arg_10 */
                                 int rice_initialhistory, /* arg424->b */
                                 int rice_kmodifier, /* arg424->d */
                                 int rice_historymult, /* arg424->c */
                                 int rice_kmodifier_mask /* arg424->e */
        )
{
    int output_count;
    unsigned int history = rice_initialhistory;
    int sign_modifier = 0;

    for (output_count = 0; output_count < output_size; output_count++)
    {
        int32_t x = 0;
        int32_t x_modified;
        int32_t final_val;

        /* read x - number of 1s before 0 represent the rice */
        while (x <= 8 && readbit(alac))
        {
            x++;
        }


        if (x > 8) /* RICE THRESHOLD */
        { /* use alternative encoding */