/*

 * 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 (Apple Lossless Audio Codec) decoder

 * @author 2005 David Hammerton

 * @see http://crazney.net/programs/itunes/alac.html

 *

 * Note: This decoder expects a 36-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:

 *

 * 32 bits  atom size

 * 32 bits  tag                  ("alac")

 * 32 bits  tag version          (0)

 * 32 bits  samples per frame    (used when not set explicitly in the frames)

 *  8 bits  compatible version   (0)

 *  8 bits  sample size

 *  8 bits  history mult         (40)

 *  8 bits  initial history      (10)

 *  8 bits  rice param limit     (14)

 *  8 bits  channels

 * 16 bits  maxRun               (255)

 * 32 bits  max coded frame size (0 means unknown)

 * 32 bits  average bitrate      (0 means unknown)

 * 32 bits  samplerate

 */

#include <inttypes.h>

#include "libavutil/channel_layout.h"

#include "libavutil/mem.h"

#include "libavutil/opt.h"

#include "avcodec.h"

#include "get_bits.h"

#include "bytestream.h"

#include "codec_internal.h"

#include "thread.h"

#include "unary.h"

#include "mathops.h"

#include "alac_data.h"

#include "alacdsp.h"

#define ALAC_EXTRADATA_SIZE 36

typedef struct ALACContext {

    AVClass *class;

    AVCodecContext *avctx;

    GetBitContext gb;

    int channels;

    int32_t *predict_error_buffer[2];

    int32_t *output_samples_buffer[2];

    int32_t *extra_bits_buffer[2];

    uint32_t max_samples_per_frame;

    uint8_t  sample_size;

    uint8_t  rice_history_mult;

    uint8_t  rice_initial_history;

    uint8_t  rice_limit;

    int      sample_rate;

    int extra_bits;     /**< number of extra bits beyond 16-bit */

    int nb_samples;     /**< number of samples in the current frame */

    int direct_output;

    int extra_bit_bug;

    ALACDSPContext dsp;

} ALACContext;

static inline unsigned int decode_scalar(GetBitContext *gb, int k, int bps)

{

    unsigned int x = get_unary_0_9(gb);

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

        /* use alternative encoding */

        x = get_bits_long(gb, bps);

    } else 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 int rice_decompress(ALACContext *alac, int32_t *output_buffer,

                            int nb_samples, int bps, int rice_history_mult)

{

    GetBitContext *gb = &alac->gb;

    int i;

    unsigned int history = alac->rice_initial_history;

    int sign_modifier = 0;

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

        int k;

        unsigned int x;

        if (get_bits_left(gb) <= 0)

            return AVERROR_INVALIDDATA;

        /* calculate rice param and decode next value */

        k = av_log2((history >> 9) + 3);

        k = FFMIN(k, alac->rice_limit);

        x = decode_scalar(gb, k, bps);

        x += sign_modifier;

        sign_modifier = 0;

        output_buffer[i] = (x >> 1) ^ -(x & 1);

        /* update the history */

        if (x > 0xffff)

            history = 0xffff;

        else

            history +=         x * rice_history_mult -

                       ((history * rice_history_mult) >> 9);

        /* special case: there may be compressed blocks of 0 */

        if ((history < 128) && (i + 1 < nb_samples)) {

            int block_size;

            /* calculate rice param and decode block size */

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

            k = FFMIN(k, alac->rice_limit);

            block_size = decode_scalar(gb, k, 16);

            if (block_size > 0) {

                if (block_size >= nb_samples - i) {

                    av_log(alac->avctx, AV_LOG_ERROR,

                           "invalid zero block size of %d %d %d\n", block_size,

                           nb_samples, i);

                    block_size = nb_samples - i - 1;

                }

                memset(&output_buffer[i + 1], 0,

                       block_size * sizeof(*output_buffer));

                i += block_size;

            }

            if (block_size <= 0xffff)

                sign_modifier = 1;

            history = 0;

        }

    }

    return 0;

}

static inline int sign_only(int v)

{

    return FFDIFFSIGN(v, 0);

}

static void lpc_prediction(int32_t *error_buffer, uint32_t *buffer_out,

                           int nb_samples, int bps, int16_t *lpc_coefs,

                           int lpc_order, int lpc_quant)

{

    int i;

    uint32_t *pred = buffer_out;

    /* first sample always copies */

    *buffer_out = *error_buffer;

    if (nb_samples <= 1)

        return;

    if (!lpc_order) {

        memcpy(&buffer_out[1], &error_buffer[1],

               (nb_samples - 1) * sizeof(*buffer_out));

        return;

    }

    if (lpc_order == 31) {

        /* simple 1st-order prediction */

        for (i = 1; i < nb_samples; i++) {

            buffer_out[i] = sign_extend(buffer_out[i - 1] + error_buffer[i],

                                        bps);

        }

        return;

    }

    /* read warm-up samples */

    for (i = 1; i <= lpc_order && i < nb_samples; i++)

        buffer_out[i] = sign_extend(buffer_out[i - 1] + error_buffer[i], bps);

    /* NOTE: 4 and 8 are very common cases that could be optimized. */

    for (; i < nb_samples; i++) {

        int j;

        int val = 0;

        unsigned error_val = error_buffer[i];

        int error_sign;

        int d = *pred++;

        /* LPC prediction */

        for (j = 0; j < lpc_order; j++)

            val += (pred[j] - d) * lpc_coefs[j];

        val = (val + (1LL << (lpc_quant - 1))) >> lpc_quant;

        val += d + error_val;

        buffer_out[i] = sign_extend(val, bps);

        /* adapt LPC coefficients */

        error_sign = sign_only(error_val);

        if (error_sign) {

            for (j = 0; j < lpc_order && (int)(error_val * error_sign) > 0; j++) {

                int sign;

                val  = d - pred[j];

                sign = sign_only(val) * error_sign;

                lpc_coefs[j] -= sign;

                val *= (unsigned)sign;

                error_val -= (val >> lpc_quant) * (j + 1U);

            }

        }

    }

}

static int decode_element(AVCodecContext *avctx, AVFrame *frame, int ch_index,

                          int channels)

{

    ALACContext *alac = avctx->priv_data;

    int has_size, bps, is_compressed, decorr_shift, decorr_left_weight, ret;

    GetBitContext *gb = &alac->gb;

    uint32_t output_samples;

    int i, ch;

    skip_bits(gb, 4);  /* element instance tag */

    skip_bits(gb, 12); /* unused header bits */

    /* the number of output samples is stored in the frame */

    has_size = get_bits1(gb);

    alac->extra_bits = get_bits(gb, 2) << 3;

    bps = alac->sample_size - alac->extra_bits + channels - 1;

    if (bps > 32) {

        avpriv_report_missing_feature(avctx, "bps %d", bps);

        return AVERROR_PATCHWELCOME;

    }

    if (bps < 1)

        return AVERROR_INVALIDDATA;

    /* whether the frame is compressed */

    is_compressed = !get_bits1(gb);

    if (has_size)

        output_samples = get_bits_long(gb, 32);

    else

        output_samples = alac->max_samples_per_frame;

    if (!output_samples || output_samples > alac->max_samples_per_frame) {

        av_log(avctx, AV_LOG_ERROR, "invalid samples per frame: %"PRIu32"\n",

               output_samples);

        return AVERROR_INVALIDDATA;

    }

    if (!alac->nb_samples) {

        /* get output buffer */

        frame->nb_samples = output_samples;

        if ((ret = ff_thread_get_buffer(avctx, frame, 0)) < 0)

            return ret;

    } else if (output_samples != alac->nb_samples) {

        av_log(avctx, AV_LOG_ERROR, "sample count mismatch: %"PRIu32" != %d\n",

               output_samples, alac->nb_samples);

        return AVERROR_INVALIDDATA;

    }

    alac->nb_samples = output_samples;

    if (alac->direct_output) {

        for (ch = 0; ch < channels; ch++)

            alac->output_samples_buffer[ch] = (int32_t *)frame->extended_data[ch_index + ch];

    }

    if (is_compressed) {

        int16_t lpc_coefs[2][32];

        int lpc_order[2];

        int prediction_type[2];

        int lpc_quant[2];

        int rice_history_mult[2];

        if (!alac->rice_limit) {

            avpriv_request_sample(alac->avctx,

                                  "Compression with rice limit 0");

            return AVERROR(ENOSYS);

        }

        decorr_shift       = get_bits(gb, 8);

        decorr_left_weight = get_bits(gb, 8);

        if (channels == 2 && decorr_left_weight && decorr_shift > 31)

            return AVERROR_INVALIDDATA;

        for (ch = 0; ch < channels; ch++) {

            prediction_type[ch]   = get_bits(gb, 4);

            lpc_quant[ch]         = get_bits(gb, 4);

            rice_history_mult[ch] = get_bits(gb, 3);

            lpc_order[ch]         = get_bits(gb, 5);

            if (lpc_order[ch] >= alac->max_samples_per_frame || !lpc_quant[ch])

                return AVERROR_INVALIDDATA;

            /* read the predictor table */

            for (i = lpc_order[ch] - 1; i >= 0; i--)

                lpc_coefs[ch][i] = get_sbits(gb, 16);

        }

        if (alac->extra_bits) {

            const int extra_bits = alac->extra_bits;

            if (get_bits_left(gb) < (int64_t)alac->nb_samples * channels * extra_bits)

                return AVERROR_INVALIDDATA;

            for (i = 0; i < alac->nb_samples; i++) {

                for (ch = 0; ch < channels; ch++)

                    alac->extra_bits_buffer[ch][i] = get_bits(gb, extra_bits);

            }

        }

        for (ch = 0; ch < channels; ch++) {

            int ret = rice_decompress(alac, alac->predict_error_buffer[ch],

                            alac->nb_samples, bps,

                            rice_history_mult[ch] * alac->rice_history_mult / 4);

            if (ret < 0)

                return ret;

            /* adaptive FIR filter */

            if (prediction_type[ch] == 15) {

                /* Prediction type 15 runs the adaptive FIR twice.

                 * The first pass uses the special-case coef_num = 31, while

                 * the second pass uses the coefs from the bitstream.

                 *

                 * However, this prediction type is not currently used by the

                 * reference encoder.

                 */

                lpc_prediction(alac->predict_error_buffer[ch],

                               alac->predict_error_buffer[ch],

                               alac->nb_samples, bps, NULL, 31, 0);

            } else if (prediction_type[ch] > 0) {

                av_log(avctx, AV_LOG_WARNING, "unknown prediction type: %i\n",

                       prediction_type[ch]);

            }

            lpc_prediction(alac->predict_error_buffer[ch],

                           alac->output_samples_buffer[ch], alac->nb_samples,

                           bps, lpc_coefs[ch], lpc_order[ch], lpc_quant[ch]);

        }

    } else {

        const int sample_size = alac->sample_size;

        /* not compressed, easy case */

        if (get_bits_left(gb) < (int64_t)alac->nb_samples * channels * sample_size)

            return AVERROR_INVALIDDATA;

        for (i = 0; i < alac->nb_samples; i++) {

            for (ch = 0; ch < channels; ch++) {

                alac->output_samples_buffer[ch][i] =

                         get_sbits_long(gb, sample_size);

            }

        }

        alac->extra_bits   = 0;

        decorr_shift       = 0;

        decorr_left_weight = 0;

    }

    if (channels == 2) {

        if (alac->extra_bits && alac->extra_bit_bug) {

            alac->dsp.append_extra_bits[1](alac->output_samples_buffer, alac->extra_bits_buffer,

                                           alac->extra_bits, channels, alac->nb_samples);

        }

        if (decorr_left_weight) {

            alac->dsp.decorrelate_stereo(alac->output_samples_buffer, alac->nb_samples,

                                         decorr_shift, decorr_left_weight);

        }

        if (alac->extra_bits && !alac->extra_bit_bug) {

            alac->dsp.append_extra_bits[1](alac->output_samples_buffer, alac->extra_bits_buffer,

                                           alac->extra_bits, channels, alac->nb_samples);

        }

    } else if (alac->extra_bits) {

        alac->dsp.append_extra_bits[0](alac->output_samples_buffer, alac->extra_bits_buffer,

                                       alac->extra_bits, channels, alac->nb_samples);

    }

    switch(alac->sample_size) {

    case 16: {

        for (ch = 0; ch < channels; ch++) {

            int16_t *outbuffer = (int16_t *)frame->extended_data[ch_index + ch];

            for (i = 0; i < alac->nb_samples; i++)

                *outbuffer++ = alac->output_samples_buffer[ch][i];

        }}

        break;

    case 20: {

        for (ch = 0; ch < channels; ch++) {

            for (i = 0; i < alac->nb_samples; i++)

                alac->output_samples_buffer[ch][i] *= 1U << 12;

        }}

        break;

    case 24: {

        for (ch = 0; ch < channels; ch++) {

            for (i = 0; i < alac->nb_samples; i++)

                alac->output_samples_buffer[ch][i] *= 1U << 8;

        }}

        break;

    }

    return 0;

}

static int alac_decode_frame(AVCodecContext *avctx, AVFrame *frame,

                             int *got_frame_ptr, AVPacket *avpkt)

{

    ALACContext *alac = avctx->priv_data;

    enum AlacRawDataBlockType element;

    int channels;

    int ch, ret, got_end;

    if ((ret = init_get_bits8(&alac->gb, avpkt->data, avpkt->size)) < 0)

        return ret;

    got_end = 0;

    alac->nb_samples = 0;

    ch = 0;

    while (get_bits_left(&alac->gb) >= 3) {

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

        if (element == TYPE_END) {

            got_end = 1;

            break;

        }

        if (element > TYPE_CPE && element != TYPE_LFE) {

            avpriv_report_missing_feature(avctx, "Syntax element %d", element);

            return AVERROR_PATCHWELCOME;

        }

        channels = (element == TYPE_CPE) ? 2 : 1;

        if (ch + channels > alac->channels ||

            ff_alac_channel_layout_offsets[alac->channels - 1][ch] + channels > alac->channels) {

            av_log(avctx, AV_LOG_ERROR, "invalid element channel count\n");

            return AVERROR_INVALIDDATA;

        }

        ret = decode_element(avctx, frame,

                             ff_alac_channel_layout_offsets[alac->channels - 1][ch],

                             channels);

        if (ret < 0 && get_bits_left(&alac->gb))

            return ret;

        ch += channels;

    }

    if (!got_end) {

        av_log(avctx, AV_LOG_ERROR, "no end tag found. incomplete packet.\n");

        return AVERROR_INVALIDDATA;

    }

    if (avpkt->size * 8 - get_bits_count(&alac->gb) > 8) {

        av_log(avctx, AV_LOG_ERROR, "Error : %d bits left\n",

               avpkt->size * 8 - get_bits_count(&alac->gb));

    }

    if (alac->channels == ch && alac->nb_samples)

        *got_frame_ptr = 1;

    else

        av_log(avctx, AV_LOG_WARNING, "Failed to decode all channels\n");

    return avpkt->size;

}

static av_cold int alac_decode_close(AVCodecContext *avctx)

{

    ALACContext *alac = avctx->priv_data;

    int ch;

    for (ch = 0; ch < FFMIN(alac->channels, 2); ch++) {

        av_freep(&alac->predict_error_buffer[ch]);

        if (!alac->direct_output)

            av_freep(&alac->output_samples_buffer[ch]);

        av_freep(&alac->extra_bits_buffer[ch]);

    }

    return 0;

}

static int allocate_buffers(ALACContext *alac)

{

    int ch;

    unsigned buf_size = alac->max_samples_per_frame * sizeof(int32_t);

    unsigned extra_buf_size = buf_size + AV_INPUT_BUFFER_PADDING_SIZE;

    for (ch = 0; ch < 2; ch++) {

        alac->predict_error_buffer[ch]  = NULL;

        alac->output_samples_buffer[ch] = NULL;

        alac->extra_bits_buffer[ch]     = NULL;

    }

    for (ch = 0; ch < FFMIN(alac->channels, 2); ch++) {

        if (!(alac->predict_error_buffer[ch] = av_malloc(buf_size)))

            return AVERROR(ENOMEM);

        alac->direct_output = alac->sample_size > 16;

        if (!alac->direct_output) {

            if (!(alac->output_samples_buffer[ch] = av_malloc(extra_buf_size)))

                return AVERROR(ENOMEM);

        }

        if (!(alac->extra_bits_buffer[ch] = av_malloc(extra_buf_size)))

            return AVERROR(ENOMEM);

    }

    return 0;

}

static int alac_set_info(ALACContext *alac)

{

    GetByteContext gb;

    bytestream2_init(&gb, alac->avctx->extradata,

                     alac->avctx->extradata_size);

    bytestream2_skipu(&gb, 12); // size:4, alac:4, version:4

    alac->max_samples_per_frame = bytestream2_get_be32u(&gb);

    if (!alac->max_samples_per_frame ||

        alac->max_samples_per_frame > 4096 * 4096) {

        av_log(alac->avctx, AV_LOG_ERROR,

               "max samples per frame invalid: %"PRIu32"\n",

               alac->max_samples_per_frame);

        return AVERROR_INVALIDDATA;

    }

    bytestream2_skipu(&gb, 1);  // compatible version

    alac->sample_size          = bytestream2_get_byteu(&gb);

    alac->rice_history_mult    = bytestream2_get_byteu(&gb);

    alac->rice_initial_history = bytestream2_get_byteu(&gb);

    alac->rice_limit           = bytestream2_get_byteu(&gb);

    alac->channels             = bytestream2_get_byteu(&gb);

    bytestream2_get_be16u(&gb); // maxRun

    bytestream2_get_be32u(&gb); // max coded frame size

    bytestream2_get_be32u(&gb); // average bitrate

    alac->sample_rate          = bytestream2_get_be32u(&gb);

    return 0;

}

static av_cold int alac_decode_init(AVCodecContext * avctx)

{

    int ret;

    ALACContext *alac = avctx->priv_data;

    alac->avctx = avctx;

    /* initialize from the extradata */

    if (alac->avctx->extradata_size < ALAC_EXTRADATA_SIZE) {

        av_log(avctx, AV_LOG_ERROR, "extradata is too small\n");

        return AVERROR_INVALIDDATA;

    }

    if ((ret = alac_set_info(alac)) < 0) {

        av_log(avctx, AV_LOG_ERROR, "set_info failed\n");

        return ret;

    }

    switch (alac->sample_size) {

    case 16: avctx->sample_fmt = AV_SAMPLE_FMT_S16P;

             break;

    case 20:

    case 24:

    case 32: avctx->sample_fmt = AV_SAMPLE_FMT_S32P;

             break;

    default: avpriv_request_sample(avctx, "Sample depth %d", alac->sample_size);

             return AVERROR_PATCHWELCOME;

    }

    avctx->bits_per_raw_sample = alac->sample_size;

    avctx->sample_rate         = alac->sample_rate;

    if (alac->channels < 1) {

        av_log(avctx, AV_LOG_WARNING, "Invalid channel count\n");

        if (avctx->ch_layout.nb_channels < 1)

            return AVERROR(EINVAL);

        alac->channels = avctx->ch_layout.nb_channels;

    }

    if (alac->channels > ALAC_MAX_CHANNELS) {

        avpriv_report_missing_feature(avctx, "Channel count %d",

                                      alac->channels);

        return AVERROR_PATCHWELCOME;

    }

    av_channel_layout_uninit(&avctx->ch_layout);

    avctx->ch_layout = ff_alac_ch_layouts[alac->channels - 1];

    if ((ret = allocate_buffers(alac)) < 0) {

        av_log(avctx, AV_LOG_ERROR, "Error allocating buffers\n");

        return ret;

    }

    ff_alacdsp_init(&alac->dsp);

    return 0;

}

static const AVOption options[] = {

    { "extra_bits_bug", "Force non-standard decoding process",

      offsetof(ALACContext, extra_bit_bug), AV_OPT_TYPE_BOOL, { .i64 = 0 },

      0, 1, AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_DECODING_PARAM },

    { NULL },

};

static const AVClass alac_class = {

    .class_name = "alac",

    .item_name  = av_default_item_name,

    .option     = options,

    .version    = LIBAVUTIL_VERSION_INT,

};

const FFCodec ff_alac_decoder = {

    .p.name         = "alac",

    CODEC_LONG_NAME("ALAC (Apple Lossless Audio Codec)"),

    .p.type         = AVMEDIA_TYPE_AUDIO,

    .p.id           = AV_CODEC_ID_ALAC,

    .priv_data_size = sizeof(ALACContext),

    .init           = alac_decode_init,

    .close          = alac_decode_close,

    FF_CODEC_DECODE_CB(alac_decode_frame),

    .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_FRAME_THREADS | AV_CODEC_CAP_CHANNEL_CONF,

    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,

    .p.priv_class   = &alac_class

};