alac.c

ffmpeg移植到symbian的全部源代码

/*
 * ALAC (Apple Lossless Audio Codec) decoder
 * Copyright (c) 2005 David Hammerton
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file alac.c
 * ALAC (Apple Lossless Audio Codec) decoder
 * @author 2005 David Hammerton
 *
 * For more information on the ALAC format, visit:
 *  http://crazney.net/programs/itunes/alac.html
 *
 * Note: This decoder expects a 36- (0x24-)byte QuickTime atom to be
 * passed through the extradata[_size] fields. This atom is tacked onto
 * the end of an 'alac' stsd atom and has the following format:
 *  bytes 0-3   atom size (0x24), big-endian
 *  bytes 4-7   atom type ('alac', not the 'alac' tag from start of stsd)
 *  bytes 8-35  data bytes needed by decoder
 *
 * Extradata:
 * 32bit  size
 * 32bit  tag (=alac)
 * 32bit  zero?
 * 32bit  max sample per frame
 *  8bit  ?? (zero?)
 *  8bit  sample size
 *  8bit  history mult
 *  8bit  initial history
 *  8bit  kmodifier
 *  8bit  channels?
 * 16bit  ??
 * 32bit  max coded frame size
 * 32bit  bitrate?
 * 32bit  samplerate
 */


#include "avcodec.h"
#include "bitstream.h"
#include "bytestream.h"
#include "unary.h"

#define ALAC_EXTRADATA_SIZE 36
#define MAX_CHANNELS 2

typedef struct {

    AVCodecContext *avctx;
    GetBitContext gb;
    /* init to 0; first frame decode should initialize from extradata and
     * set this to 1 */
    int context_initialized;

    int numchannels;
    int bytespersample;

    /* buffers */
    int32_t *predicterror_buffer[MAX_CHANNELS];

    int32_t *outputsamples_buffer[MAX_CHANNELS];

    /* stuff from setinfo */
    uint32_t setinfo_max_samples_per_frame; /* 0x1000 = 4096 */    /* max samples per frame? */
    uint8_t setinfo_sample_size; /* 0x10 */
    uint8_t setinfo_rice_historymult; /* 0x28 */
    uint8_t setinfo_rice_initialhistory; /* 0x0a */
    uint8_t setinfo_rice_kmodifier; /* 0x0e */
    /* end setinfo stuff */

} ALACContext;

static void allocate_buffers(ALACContext *alac)
{
    int chan;
    for (chan = 0; chan < MAX_CHANNELS; chan++) {
        alac->predicterror_buffer[chan] =
            av_malloc(alac->setinfo_max_samples_per_frame * 4);

        alac->outputsamples_buffer[chan] =
            av_malloc(alac->setinfo_max_samples_per_frame * 4);
    }
}

static int alac_set_info(ALACContext *alac)
{
    const unsigned char *ptr = alac->avctx->extradata;

    ptr += 4; /* size */
    ptr += 4; /* alac */
    ptr += 4; /* 0 ? */

    if(AV_RB32(ptr) >= UINT_MAX/4){
        av_log(alac->avctx, AV_LOG_ERROR, "setinfo_max_samples_per_frame too large\n");
        return -1;
    }

    /* buffer size / 2 ? */
    alac->setinfo_max_samples_per_frame = bytestream_get_be32(&ptr);
    ptr++;                          /* ??? */
    alac->setinfo_sample_size           = *ptr++;
    if (alac->setinfo_sample_size > 32) {
        av_log(alac->avctx, AV_LOG_ERROR, "setinfo_sample_size too large\n");
        return -1;
    }
    alac->setinfo_rice_historymult      = *ptr++;
    alac->setinfo_rice_initialhistory   = *ptr++;
    alac->setinfo_rice_kmodifier        = *ptr++;
    ptr++;                         /* channels? */
    bytestream_get_be16(&ptr);      /* ??? */
    bytestream_get_be32(&ptr);      /* max coded frame size */
    bytestream_get_be32(&ptr);      /* bitrate ? */
    bytestream_get_be32(&ptr);      /* samplerate */

    allocate_buffers(alac);

    return 0;
}

static inline int decode_scalar(GetBitContext *gb, int k, int limit, int readsamplesize){
    /* read x - number of 1s before 0 represent the rice */
    int x = get_unary_0_9(gb);

    if (x > 8) { /* RICE THRESHOLD */
        /* use alternative encoding */
        x = get_bits(gb, readsamplesize);
    } else {
        if (k >= limit)
            k = limit;

        if (k != 1) {
            int extrabits = show_bits(gb, k);

            /* multiply x by 2^k - 1, as part of their strange algorithm */
            x = (x << k) - x;

            if (extrabits > 1) {
                x += extrabits - 1;
                skip_bits(gb, k);
            } else
                skip_bits(gb, k - 1);
        }
    }
    return x;
}

static void bastardized_rice_decompress(ALACContext *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;
        int32_t x_modified;
        int32_t final_val;

        /* standard rice encoding */
        int k; /* size of extra bits */

        /* read k, that is bits as is */
        k = av_log2((history >> 9) + 3);
        x= decode_scalar(&alac->gb, k, rice_kmodifier, readsamplesize);

        x_modified = sign_modifier + x;
        final_val = (x_modified + 1) / 2;
        if (x_modified & 1) final_val *= -1;

        output_buffer[output_count] = final_val;

        sign_modifier = 0;

        /* now update the history */
        history += x_modified * rice_historymult
                   - ((history * rice_historymult) >> 9);

        if (x_modified > 0xffff)
            history = 0xffff;

        /* special case: there may be compressed blocks of 0 */
        if ((history < 128) && (output_count+1 < output_size)) {
            int k;
            unsigned int block_size;

            sign_modifier = 1;

            k = 7 - av_log2(history) + ((history + 16) >> 6 /* / 64 */);

            block_size= decode_scalar(&alac->gb, k, rice_kmodifier, 16);

            if (block_size > 0) {
                if(block_size >= output_size - output_count){
                    av_log(alac->avctx, AV_LOG_ERROR, "invalid zero block size of %d %d %d\n", block_size, output_size, output_count);
                    block_size= output_size - output_count - 1;
                }
                memset(&output_buffer[output_count+1], 0, block_size * 4);
                output_count += block_size;
            }

            if (block_size > 0xffff)
                sign_modifier = 0;

            history = 0;
        }
    }
}

static inline int32_t extend_sign32(int32_t val, int bits)
{
    return (val << (32 - bits)) >> (32 - bits);
}

static inline int sign_only(int v)
{
    return v ? FFSIGN(v) : 0;
}

static void predictor_decompress_fir_adapt(int32_t *error_buffer,
                                           int32_t *buffer_out,
                                           int output_size,
                                           int readsamplesize,
                                           int16_t *predictor_coef_table,
                                           int predictor_coef_num,
                                           int predictor_quantitization)
{
    int i;

    /* first sample always copies */
    *buffer_out = *error_buffer;

    if (!predictor_coef_num) {
        if (output_size <= 1)
            return;

        memcpy(buffer_out+1, error_buffer+1, (output_size-1) * 4);
        return;
    }

    if (predictor_coef_num == 0x1f) { /* 11111 - max value of predictor_coef_num */
      /* second-best case scenario for fir decompression,
       * error describes a small difference from the previous sample only
       */
        if (output_size <= 1)
            return;
        for (i = 0; i < output_size - 1; i++) {
            int32_t prev_value;
            int32_t error_value;

            prev_value = buffer_out[i];
            error_value = error_buffer[i+1];
            buffer_out[i+1] =
                extend_sign32((prev_value + error_value), readsamplesize);
        }
        return;
    }

    /* read warm-up samples */
    if (predictor_coef_num > 0)
        for (i = 0; i < predictor_coef_num; i++) {
            int32_t val;

            val = buffer_out[i] + error_buffer[i+1];
            val = extend_sign32(val, readsamplesize);
            buffer_out[i+1] = val;
        }

#if 0
    /* 4 and 8 are very common cases (the only ones i've seen). these
     * should be unrolled and optimized
     */
    if (predictor_coef_num == 4) {
        /* FIXME: optimized general case */
        return;
    }

    if (predictor_coef_table == 8) {
        /* FIXME: optimized general case */
        return;
    }
#endif

    /* general case */
    if (predictor_coef_num > 0) {
        for (i = predictor_coef_num + 1; i < output_size; i++) {
            int j;
            int sum = 0;
            int outval;
            int error_val = error_buffer[i];

            for (j = 0; j < predictor_coef_num; j++) {
                sum += (buffer_out[predictor_coef_num-j] - buffer_out[0]) *
                       predictor_coef_table[j];
            }

            outval = (1 << (predictor_quantitization-1)) + sum;
            outval = outval >> predictor_quantitization;
            outval = outval + buffer_out[0] + error_val;
            outval = extend_sign32(outval, readsamplesize);

            buffer_out[predictor_coef_num+1] = outval;

            if (error_val > 0) {
                int predictor_num = predictor_coef_num - 1;