PeerStreamer

/*

 * ALAC (Apple Lossless Audio Codec) decoder

 * Copyright (c) 2005 David Hammerton

 * All rights reserved.

 *

 * This library 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 of the License, or (at your option) any later version.

 *

 * This library 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 this library; 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

 */

#include "avcodec.h"

#include "bitstream.h"

#define ALAC_EXTRADATA_SIZE 36

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 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 */

    uint32_t setinfo_86; /* 0x00069fe4 */

    uint32_t setinfo_8a_rate; /* 0x0000ac44 */

    /* end setinfo stuff */

} ALACContext;

static void allocate_buffers(ALACContext *alac)

{

    alac->predicterror_buffer_a = av_malloc(alac->setinfo_max_samples_per_frame * 4);

    alac->predicterror_buffer_b = av_malloc(alac->setinfo_max_samples_per_frame * 4);

    alac->outputsamples_buffer_a = av_malloc(alac->setinfo_max_samples_per_frame * 4);

    alac->outputsamples_buffer_b = av_malloc(alac->setinfo_max_samples_per_frame * 4);

}

void alac_set_info(ALACContext *alac)

{

    unsigned char *ptr = alac->avctx->extradata;

    ptr += 4; /* size */

    ptr += 4; /* alac */

    ptr += 4; /* 0 ? */

    alac->setinfo_max_samples_per_frame = BE_32(ptr); /* buffer size / 2 ? */

    ptr += 4;

    alac->setinfo_7a = *ptr++;

    alac->setinfo_sample_size = *ptr++;

    alac->setinfo_rice_historymult = *ptr++;

    alac->setinfo_rice_initialhistory = *ptr++;

    alac->setinfo_rice_kmodifier = *ptr++;

    alac->setinfo_7f = *ptr++;

    alac->setinfo_80 = BE_16(ptr);

    ptr += 2;

    alac->setinfo_82 = BE_32(ptr);

    ptr += 4;

    alac->setinfo_86 = BE_32(ptr);

    ptr += 4;

    alac->setinfo_8a_rate = BE_32(ptr);

    ptr += 4;

    allocate_buffers(alac);

}

/* 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;

}

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 = 0;

        int32_t x_modified;

        int32_t final_val;

        /* read x - number of 1s before 0 represent the rice */

        while (x <= 8 && get_bits1(&alac->gb)) {

            x++;

        }

        if (x > 8) { /* RICE THRESHOLD */

          /* use alternative encoding */

            int32_t value;

            value = get_bits(&alac->gb, readsamplesize);

            /* mask value to readsamplesize size */

            if (readsamplesize != 32)

                value &= (0xffffffff >> (32 - readsamplesize));

            x = value;

        } else {

          /* standard rice encoding */

            int extrabits;

            int k; /* size of extra bits */

            /* read k, that is bits as is */

            k = 31 - rice_kmodifier - count_leading_zeros((history >> 9) + 3);

            if (k < 0)

                k += rice_kmodifier;

            else

                k = rice_kmodifier;

            if (k != 1) {

                extrabits = show_bits(&alac->gb, k);

                /* multiply x by 2^k - 1, as part of their strange algorithm */

                x = (x << k) - x;

                if (extrabits > 1) {

                    x += extrabits - 1;

                    get_bits(&alac->gb, k);

                } else {

                    get_bits(&alac->gb, k - 1);

                }

            }

        }

        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 block_size;

            sign_modifier = 1;

            x = 0;

            while (x <= 8 && get_bits1(&alac->gb)) {

                x++;

            }

            if (x > 8) {

                block_size = get_bits(&alac->gb, 16);

                block_size &= 0xffff;

            } else {

                int k;

                int extrabits;

                k = count_leading_zeros(history) + ((history + 16) >> 6 /* / 64 */) - 24;

                extrabits = show_bits(&alac->gb, k);

                block_size = (((1 << k) - 1) & rice_kmodifier_mask) * x

                           + extrabits - 1;

                if (extrabits < 2) {

                    x = 1 - extrabits;

                    block_size += x;

                    get_bits(&alac->gb, k - 1);

                } else {

                    get_bits(&alac->gb, k);

                }

            }

            if (block_size > 0) {

                memset(&output_buffer[output_count+1], 0, block_size * 4);

                output_count += block_size;

            }

            if (block_size > 0xffff)

                sign_modifier = 0;

            history = 0;

        }

    }

}

#define SIGN_EXTENDED32(val, bits) ((val << (32 - bits)) >> (32 - bits))

#define SIGN_ONLY(v) \

                     ((v < 0) ? (-1) : \

                                ((v > 0) ? (1) : \

                                           (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] = SIGN_EXTENDED32((prev_value + error_value), readsamplesize);

        }

        return;

    }

    /* read warm-up samples */

    if (predictor_coef_num > 0) {

        int i;

        for (i = 0; i < predictor_coef_num; i++) {

            int32_t val;

            val = buffer_out[i] + error_buffer[i+1];

            val = SIGN_EXTENDED32(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 optimised

     */

    if (predictor_coef_num == 4) {

        /* FIXME: optimised general case */

        return;

    }

    if (predictor_coef_table == 8) {

        /* FIXME: optimised 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 = SIGN_EXTENDED32(outval, readsamplesize);

            buffer_out[predictor_coef_num+1] = outval;

            if (error_val > 0) {

                int predictor_num = predictor_coef_num - 1;

                while (predictor_num >= 0 && error_val > 0) {

                    int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];

                    int sign = SIGN_ONLY(val);

                    predictor_coef_table[predictor_num] -= sign;

                    val *= sign; /* absolute value */

                    error_val -= ((val >> predictor_quantitization) *

                                  (predictor_coef_num - predictor_num));

                    predictor_num--;

                }

            } else if (error_val < 0) {

                int predictor_num = predictor_coef_num - 1;

                while (predictor_num >= 0 && error_val < 0) {

                    int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];

                    int sign = - SIGN_ONLY(val);

                    predictor_coef_table[predictor_num] -= sign;

                    val *= sign; /* neg value */

                    error_val -= ((val >> predictor_quantitization) *

                                  (predictor_coef_num - predictor_num));

                    predictor_num--;

                }

            }

            buffer_out++;

        }

    }

}

void deinterlace_16(int32_t *buffer_a, int32_t *buffer_b,

                    int16_t *buffer_out,

                    int numchannels, int numsamples,

                    uint8_t interlacing_shift,

                    uint8_t interlacing_leftweight)

{

    int i;

    if (numsamples <= 0) return;

    /* weighted interlacing */

    if (interlacing_leftweight) {

        for (i = 0; i < numsamples; i++) {

            int32_t difference, midright;

            int16_t left;

            int16_t right;

            midright = buffer_a[i];

            difference = buffer_b[i];

            right = midright - ((difference * interlacing_leftweight) >> interlacing_shift);

            left = (midright - ((difference * interlacing_leftweight) >> interlacing_shift))

                 + difference;

            buffer_out[i*numchannels] = left;

            buffer_out[i*numchannels + 1] = right;

        }

        return;

    }

    /* otherwise basic interlacing took place */

    for (i = 0; i < numsamples; i++) {

        int16_t left, right;

        left = buffer_a[i];

        right = buffer_b[i];

        buffer_out[i*numchannels] = left;

        buffer_out[i*numchannels + 1] = right;

    }

}

static int alac_decode_frame(AVCodecContext *avctx,

                             void *outbuffer, int *outputsize,

                             uint8_t *inbuffer, int input_buffer_size)

{

    ALACContext *alac = avctx->priv_data;

    int channels;

    int32_t outputsamples;

    /* short-circuit null buffers */

    if (!inbuffer || !input_buffer_size)

        return input_buffer_size;

    /* initialize from the extradata */

    if (!alac->context_initialized) {

        if (alac->avctx->extradata_size != ALAC_EXTRADATA_SIZE) {

            av_log(NULL, AV_LOG_ERROR, "alac: expected %d extradata bytes\n",

                ALAC_EXTRADATA_SIZE);

            return input_buffer_size;

        }

        alac_set_info(alac);

        alac->context_initialized = 1;

    }

    outputsamples = alac->setinfo_max_samples_per_frame;

    init_get_bits(&alac->gb, inbuffer, input_buffer_size * 8);

    channels = get_bits(&alac->gb, 3);

    *outputsize = outputsamples * alac->bytespersample;

    switch(channels) {

    case 0: { /* 1 channel */

        int hassize;

        int isnotcompressed;

        int readsamplesize;

        int wasted_bytes;

        int ricemodifier;

        /* 2^result = something to do with output waiting.

         * perhaps matters if we read > 1 frame in a pass?

         */

        get_bits(&alac->gb, 4);

        get_bits(&alac->gb, 12); /* unknown, skip 12 bits */

        hassize = get_bits(&alac->gb, 1); /* the output sample size is stored soon */

        wasted_bytes = get_bits(&alac->gb, 2); /* unknown ? */

        isnotcompressed = get_bits(&alac->gb, 1); /* whether the frame is compressed */

        if (hassize) {

            /* now read the number of samples,

             * as a 32bit integer */

            outputsamples = get_bits(&alac->gb, 32);

            *outputsize = outputsamples * alac->bytespersample;

        }

        readsamplesize = alac->setinfo_sample_size - (wasted_bytes * 8);

        if (!isnotcompressed) {

         /* so it is compressed */

            int16_t predictor_coef_table[32];

            int predictor_coef_num;

            int prediction_type;

            int prediction_quantitization;

            int i;

            /* skip 16 bits, not sure what they are. seem to be used in

             * two channel case */

            get_bits(&alac->gb, 8);

            get_bits(&alac->gb, 8);

            prediction_type = get_bits(&alac->gb, 4);

            prediction_quantitization = get_bits(&alac->gb, 4);

            ricemodifier = get_bits(&alac->gb, 3);

            predictor_coef_num = get_bits(&alac->gb, 5);

            /* read the predictor table */

            for (i = 0; i < predictor_coef_num; i++) {

                predictor_coef_table[i] = (int16_t)get_bits(&alac->gb, 16);

            }

            if (wasted_bytes) {

                /* these bytes seem to have something to do with

                 * > 2 channel files.

                 */

                av_log(NULL, AV_LOG_ERROR, "FIXME: unimplemented, unhandling of wasted_bytes\n");

            }

            bastardized_rice_decompress(alac,

                                        alac->predicterror_buffer_a,

                                        outputsamples,

                                        readsamplesize,

                                        alac->setinfo_rice_initialhistory,

                                        alac->setinfo_rice_kmodifier,

                                        ricemodifier * alac->setinfo_rice_historymult / 4,

                                        (1 << alac->setinfo_rice_kmodifier) - 1);

            if (prediction_type == 0) {

              /* adaptive fir */

                predictor_decompress_fir_adapt(alac->predicterror_buffer_a,

                                               alac->outputsamples_buffer_a,

                                               outputsamples,

                                               readsamplesize,

                                               predictor_coef_table,

                                               predictor_coef_num,

                                               prediction_quantitization);

            } else {

                av_log(NULL, AV_LOG_ERROR, "FIXME: unhandled prediction type: %i\n", prediction_type);

                /* i think the only other prediction type (or perhaps this is just a

                 * boolean?) runs adaptive fir twice.. like:

                 * predictor_decompress_fir_adapt(predictor_error, tempout, ...)

                 * predictor_decompress_fir_adapt(predictor_error, outputsamples ...)

                 * little strange..

                 */

            }

        } else {

          /* not compressed, easy case */

            if (readsamplesize <= 16) {

                int i;

                for (i = 0; i < outputsamples; i++) {

                    int32_t audiobits = get_bits(&alac->gb, readsamplesize);

                    audiobits = SIGN_EXTENDED32(audiobits, readsamplesize);

                    alac->outputsamples_buffer_a[i] = audiobits;

                }

            } else {

                int i;

                for (i = 0; i < outputsamples; i++) {

                    int32_t audiobits;

                    audiobits = get_bits(&alac->gb, 16);

                    /* special case of sign extension..

                     * as we'll be ORing the low 16bits into this */

                    audiobits = audiobits << 16;

                    audiobits = audiobits >> (32 - readsamplesize);

                    audiobits |= get_bits(&alac->gb, readsamplesize - 16);

                    alac->outputsamples_buffer_a[i] = audiobits;

                }

            }

            /* wasted_bytes = 0; // unused */

        }

        switch(alac->setinfo_sample_size) {

        case 16: {

            int i;

            for (i = 0; i < outputsamples; i++) {

                int16_t sample = alac->outputsamples_buffer_a[i];

                sample = be2me_16(sample);

                ((int16_t*)outbuffer)[i * alac->numchannels] = sample;

            }

            break;

        }

        case 20:

        case 24:

        case 32:

            av_log(NULL, AV_LOG_ERROR, "FIXME: unimplemented sample size %i\n", alac->setinfo_sample_size);

            break;

        default:

            break;

        }

        break;

    }

    case 1: { /* 2 channels */

        int hassize;

        int isnotcompressed;

        int readsamplesize;

        int wasted_bytes;

        uint8_t interlacing_shift;

        uint8_t interlacing_leftweight;

        /* 2^result = something to do with output waiting.

         * perhaps matters if we read > 1 frame in a pass?

         */

        get_bits(&alac->gb, 4);

        get_bits(&alac->gb, 12); /* unknown, skip 12 bits */

        hassize = get_bits(&alac->gb, 1); /* the output sample size is stored soon */

        wasted_bytes = get_bits(&alac->gb, 2); /* unknown ? */

        isnotcompressed = get_bits(&alac->gb, 1); /* whether the frame is compressed */

        if (hassize) {

            /* now read the number of samples,

             * as a 32bit integer */

            outputsamples = get_bits(&alac->gb, 32);

            *outputsize = outputsamples * alac->bytespersample;

        }

        readsamplesize = alac->setinfo_sample_size - (wasted_bytes * 8) + 1;

        if (!isnotcompressed) {

         /* compressed */

            int16_t predictor_coef_table_a[32];

            int predictor_coef_num_a;

            int prediction_type_a;

            int prediction_quantitization_a;

            int ricemodifier_a;

            int16_t predictor_coef_table_b[32];

            int predictor_coef_num_b;

            int prediction_type_b;

            int prediction_quantitization_b;

            int ricemodifier_b;

            int i;

            interlacing_shift = get_bits(&alac->gb, 8);

            interlacing_leftweight = get_bits(&alac->gb, 8);

            /******** channel 1 ***********/

            prediction_type_a = get_bits(&alac->gb, 4);

            prediction_quantitization_a = get_bits(&alac->gb, 4);

            ricemodifier_a = get_bits(&alac->gb, 3);

            predictor_coef_num_a = get_bits(&alac->gb, 5);

            /* read the predictor table */

            for (i = 0; i < predictor_coef_num_a; i++) {

                predictor_coef_table_a[i] = (int16_t)get_bits(&alac->gb, 16);

            }

            /******** channel 2 *********/

            prediction_type_b = get_bits(&alac->gb, 4);

            prediction_quantitization_b = get_bits(&alac->gb, 4);

            ricemodifier_b = get_bits(&alac->gb, 3);

            predictor_coef_num_b = get_bits(&alac->gb, 5);

            /* read the predictor table */

            for (i = 0; i < predictor_coef_num_b; i++) {

                predictor_coef_table_b[i] = (int16_t)get_bits(&alac->gb, 16);

            }

            /*********************/

            if (wasted_bytes) {

              /* see mono case */

                av_log(NULL, AV_LOG_ERROR, "FIXME: unimplemented, unhandling of wasted_bytes\n");

            }

            /* channel 1 */

            bastardized_rice_decompress(alac,

                                        alac->predicterror_buffer_a,

                                        outputsamples,

                                        readsamplesize,

                                        alac->setinfo_rice_initialhistory,

                                        alac->setinfo_rice_kmodifier,

                                        ricemodifier_a * alac->setinfo_rice_historymult / 4,

                                        (1 << alac->setinfo_rice_kmodifier) - 1);

            if (prediction_type_a == 0) {

              /* adaptive fir */

                predictor_decompress_fir_adapt(alac->predicterror_buffer_a,

                                               alac->outputsamples_buffer_a,

                                               outputsamples,

                                               readsamplesize,

                                               predictor_coef_table_a,

                                               predictor_coef_num_a,

                                               prediction_quantitization_a);

            } else {

              /* see mono case */

                av_log(NULL, AV_LOG_ERROR, "FIXME: unhandled prediction type: %i\n", prediction_type_a);

            }

            /* channel 2 */

            bastardized_rice_decompress(alac,

                                        alac->predicterror_buffer_b,

                                        outputsamples,

                                        readsamplesize,

                                        alac->setinfo_rice_initialhistory,

                                        alac->setinfo_rice_kmodifier,

                                        ricemodifier_b * alac->setinfo_rice_historymult / 4,

                                        (1 << alac->setinfo_rice_kmodifier) - 1);

            if (prediction_type_b == 0) {

              /* adaptive fir */

                predictor_decompress_fir_adapt(alac->predicterror_buffer_b,

                                               alac->outputsamples_buffer_b,

                                               outputsamples,

                                               readsamplesize,

                                               predictor_coef_table_b,

                                               predictor_coef_num_b,

                                               prediction_quantitization_b);

            } else {

                av_log(NULL, AV_LOG_ERROR, "FIXME: unhandled prediction type: %i\n", prediction_type_b);

            }

        } else {

         /* not compressed, easy case */

            if (alac->setinfo_sample_size <= 16) {

                int i;

                for (i = 0; i < outputsamples; i++) {

                    int32_t audiobits_a, audiobits_b;

                    audiobits_a = get_bits(&alac->gb, alac->setinfo_sample_size);

                    audiobits_b = get_bits(&alac->gb, alac->setinfo_sample_size);

                    audiobits_a = SIGN_EXTENDED32(audiobits_a, alac->setinfo_sample_size);

                    audiobits_b = SIGN_EXTENDED32(audiobits_b, alac->setinfo_sample_size);

                    alac->outputsamples_buffer_a[i] = audiobits_a;

                    alac->outputsamples_buffer_b[i] = audiobits_b;

                }

            } else {

                int i;

                for (i = 0; i < outputsamples; i++) {

                    int32_t audiobits_a, audiobits_b;

                    audiobits_a = get_bits(&alac->gb, 16);

                    audiobits_a = audiobits_a << 16;

                    audiobits_a = audiobits_a >> (32 - alac->setinfo_sample_size);

                    audiobits_a |= get_bits(&alac->gb, alac->setinfo_sample_size - 16);

                    audiobits_b = get_bits(&alac->gb, 16);

                    audiobits_b = audiobits_b << 16;

                    audiobits_b = audiobits_b >> (32 - alac->setinfo_sample_size);

                    audiobits_b |= get_bits(&alac->gb, alac->setinfo_sample_size - 16);

                    alac->outputsamples_buffer_a[i] = audiobits_a;

                    alac->outputsamples_buffer_b[i] = audiobits_b;

                }

            }

            /* wasted_bytes = 0; */

            interlacing_shift = 0;

            interlacing_leftweight = 0;

        }

        switch(alac->setinfo_sample_size) {

        case 16: {

            deinterlace_16(alac->outputsamples_buffer_a,

                           alac->outputsamples_buffer_b,

                           (int16_t*)outbuffer,

                           alac->numchannels,

                           outputsamples,

                           interlacing_shift,

                           interlacing_leftweight);

            break;

        }

        case 20:

        case 24:

        case 32:

            av_log(NULL, AV_LOG_ERROR, "FIXME: unimplemented sample size %i\n", alac->setinfo_sample_size);

            break;

        default:

            break;

        }

        break;

    }

    }

    return input_buffer_size;

}

static int alac_decode_init(AVCodecContext * avctx)

{

    ALACContext *alac = avctx->priv_data;

    alac->avctx = avctx;

    alac->context_initialized = 0;

    alac->samplesize = alac->avctx->bits_per_sample;

    alac->numchannels = alac->avctx->channels;

    alac->bytespersample = (alac->samplesize / 8) * alac->numchannels;

    return 0;

}

static int alac_decode_close(AVCodecContext *avctx)

{

    ALACContext *alac = avctx->priv_data;

    av_free(alac->predicterror_buffer_a);

    av_free(alac->predicterror_buffer_b);

    av_free(alac->outputsamples_buffer_a);

    av_free(alac->outputsamples_buffer_b);

    return 0;

}

AVCodec alac_decoder = {

    "alac",

    CODEC_TYPE_AUDIO,

    CODEC_ID_ALAC,

    sizeof(ALACContext),

    alac_decode_init,

    NULL,

    alac_decode_close,

    alac_decode_frame,

};