PeerStreamer

/*

 * Lagarith lossless decoder

 * Copyright (c) 2009 Nathan Caldwell <saintdev (at) gmail.com>

 *

 * 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 libavcodec/lagarith.c

 * Lagarith lossless decoder

 * @author Nathan Caldwell

 */

#include "avcodec.h"

#include "get_bits.h"

#include "mathops.h"

#include "dsputil.h"

#include "lagarithrac.h"

enum LagarithFrameType {

    FRAME_RAW           = 1,    /*!< uncompressed */

    FRAME_U_RGB24       = 2,    /*!< unaligned RGB24 */

    FRAME_ARITH_YUY2    = 3,    /*!< arithmetic coded YUY2 */

    FRAME_ARITH_RGB24   = 4,    /*!< arithmetic coded RGB24 */

    FRAME_SOLID_GRAY    = 5,    /*!< solid grayscale color frame */

    FRAME_SOLID_COLOR   = 6,    /*!< solid non-grayscale color frame */

    FRAME_OLD_ARITH_RGB = 7,    /*!< obsolete arithmetic coded RGB (no longer encoded by upstream since version 1.1.0) */

    FRAME_ARITH_RGBA    = 8,    /*!< arithmetic coded RGBA */

    FRAME_SOLID_RGBA    = 9,    /*!< solid RGBA color frame */

    FRAME_ARITH_YV12    = 10,   /*!< arithmetic coded YV12 */

    FRAME_REDUCED_RES   = 11,   /*!< reduced resolution YV12 frame */

};

typedef struct LagarithContext {

    AVCodecContext *avctx;

    AVFrame picture;

    DSPContext dsp;

    int zeros;                  /*!< number of consecutive zero bytes encountered */

    int zeros_rem;              /*!< number of zero bytes remaining to output */

} LagarithContext;

/**

 * Compute the 52bit mantissa of 1/(double)denom.

 * This crazy format uses floats in an entropy coder and we have to match x86

 * rounding exactly, thus ordinary floats aren't portable enough.

 * @param denom denominator

 * @return 52bit mantissa

 * @see softfloat_mul

 */

static uint64_t softfloat_reciprocal(uint32_t denom)

{

    int shift = av_log2(denom - 1) + 1;

    uint64_t ret = (1ULL << 52) / denom;

    uint64_t err = (1ULL << 52) - ret * denom;

    ret <<= shift;

    err <<= shift;

    err +=  denom / 2;

    return ret + err / denom;

}

/**

 * (uint32_t)(x*f), where f has the given mantissa, and exponent 0

 * Used in combination with softfloat_reciprocal computes x/(double)denom.

 * @param x 32bit integer factor

 * @param mantissa mantissa of f with exponent 0

 * @return 32bit integer value (x*f)

 * @see softfloat_reciprocal

 */

static uint32_t softfloat_mul(uint32_t x, uint64_t mantissa)

{

    uint64_t l = x * (mantissa & 0xffffffff);

    uint64_t h = x * (mantissa >> 32);

    h += l >> 32;

    l &= 0xffffffff;

    l += 1 << av_log2(h >> 21);

    h += l >> 32;

    return h >> 20;

}

static uint8_t lag_calc_zero_run(int8_t x)

{

    return (x << 1) ^ (x >> 7);

}

static int lag_decode_prob(GetBitContext *gb, uint32_t *value)

{

    static const uint8_t series[] = { 1, 2, 3, 5, 8, 13, 21 };

    int i;

    int bit     = 0;

    int bits    = 0;

    int prevbit = 0;

    unsigned val;

    for (i = 0; i < 7; i++) {

        if (prevbit && bit)

            break;

        prevbit = bit;

        bit = get_bits1(gb);

        if (bit && !prevbit)

            bits += series[i];

    }

    bits--;

    if (bits < 0 || bits > 31) {

        *value = 0;

        return -1;

    } else if (bits == 0) {

        *value = 0;

        return 0;

    }

    val  = get_bits_long(gb, bits);

    val |= 1 << bits;

    *value = val - 1;

    return 0;

}

static int lag_read_prob_header(lag_rac *rac, GetBitContext *gb)

{

    int i, j, scale_factor;

    unsigned prob, cumulative_target;

    unsigned cumul_prob = 0;

    unsigned scaled_cumul_prob = 0;

    rac->prob[0] = 0;

    rac->prob[257] = UINT_MAX;

    /* Read probabilities from bitstream */

    for (i = 1; i < 257; i++) {

        if (lag_decode_prob(gb, &rac->prob[i]) < 0) {

            av_log(rac->avctx, AV_LOG_ERROR, "Invalid probability encountered.\n");

            return -1;

        }

        if ((uint64_t)cumul_prob + rac->prob[i] > UINT_MAX) {

            av_log(rac->avctx, AV_LOG_ERROR, "Integer overflow encountered in cumulative probability calculation.\n");

            return -1;

        }

        cumul_prob += rac->prob[i];

        if (!rac->prob[i]) {

            if (lag_decode_prob(gb, &prob)) {

                av_log(rac->avctx, AV_LOG_ERROR, "Invalid probability run encountered.\n");

                return -1;

            }

            if (prob > 257 - i)

                prob = 257 - i;

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

                rac->prob[++i] = 0;

        }

    }

    if (!cumul_prob) {

        av_log(rac->avctx, AV_LOG_ERROR, "All probabilities are 0!\n");

        return -1;

    }

    /* Scale probabilities so cumulative probability is an even power of 2. */

    scale_factor = av_log2(cumul_prob);

    if (cumul_prob & (cumul_prob - 1)) {

        uint64_t mul = softfloat_reciprocal(cumul_prob);

        for (i = 1; i < 257; i++) {

            rac->prob[i] = softfloat_mul(rac->prob[i], mul);

            scaled_cumul_prob += rac->prob[i];

        }

        scale_factor++;

        cumulative_target = 1 << scale_factor;

        if (scaled_cumul_prob > cumulative_target) {

            av_log(rac->avctx, AV_LOG_ERROR,

                   "Scaled probabilities are larger than target!\n");

            return -1;

        }

        scaled_cumul_prob = cumulative_target - scaled_cumul_prob;

        for (i = 1; scaled_cumul_prob; i = (i & 0x7f) + 1) {

            if (rac->prob[i]) {

                rac->prob[i]++;

                scaled_cumul_prob--;

            }

            /* Comment from reference source:

             * if (b & 0x80 == 0) {     // order of operations is 'wrong'; it has been left this way

             *                          // since the compression change is negligable and fixing it

             *                          // breaks backwards compatibilty

             *      b =- (signed int)b;

             *      b &= 0xFF;

             * } else {

             *      b++;

             *      b &= 0x7f;

             * }

             */

        }

    }

    rac->scale = scale_factor;

    /* Fill probability array with cumulative probability for each symbol. */

    for (i = 1; i < 257; i++)

        rac->prob[i] += rac->prob[i - 1];

    return 0;

}

static void add_lag_median_prediction(uint8_t *dst, uint8_t *src1,

                                      uint8_t *diff, int w, int *left,

                                      int *left_top)

{

    /* This is almost identical to add_hfyu_median_prediction in dsputil.h.

     * However the &0xFF on the gradient predictor yealds incorrect output

     * for lagarith.

     */

    int i;

    uint8_t l, lt;

    l  = *left;

    lt = *left_top;

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

        l = mid_pred(l, src1[i], l + src1[i] - lt) + diff[i];

        lt = src1[i];

        dst[i] = l;

    }

    *left     = l;

    *left_top = lt;

}

static void lag_pred_line(LagarithContext *l, uint8_t *buf,

                          int width, int stride, int line)

{

    int L, TL;

    if (!line) {

        /* Left prediction only for first line */

        L = l->dsp.add_hfyu_left_prediction(buf + 1, buf + 1,

                                            width - 1, buf[0]);

        return;

    } else if (line == 1) {

        /* Second line, left predict first pixel, the rest of the line is median predicted */

        /* FIXME: In the case of RGB this pixel is top predicted */

        TL = buf[-stride];

    } else {

        /* Top left is 2 rows back, last pixel */

        TL = buf[width - (2 * stride) - 1];

    }

    /* Left pixel is actually prev_row[width] */

    L = buf[width - stride - 1];

    add_lag_median_prediction(buf, buf - stride, buf,

                              width, &L, &TL);

}

static int lag_decode_line(LagarithContext *l, lag_rac *rac,

                           uint8_t *dst, int width, int stride,

                           int esc_count)

{

    int i = 0;

    int ret = 0;

    if (!esc_count)

        esc_count = -1;

    /* Output any zeros remaining from the previous run */

handle_zeros:

    if (l->zeros_rem) {

        int count = FFMIN(l->zeros_rem, width - i);

        memset(dst + i, 0, count);

        i += count;

        l->zeros_rem -= count;

    }

    while (i < width) {

        dst[i] = lag_get_rac(rac);

        ret++;

        if (dst[i])

            l->zeros = 0;

        else

            l->zeros++;

        i++;

        if (l->zeros == esc_count) {

            int index = lag_get_rac(rac);

            ret++;

            l->zeros = 0;

            l->zeros_rem = lag_calc_zero_run(index);

            goto handle_zeros;

        }

    }

    return ret;

}

static int lag_decode_zero_run_line(LagarithContext *l, uint8_t *dst,

                                    const uint8_t *src, int width,

                                    int esc_count)

{

    int i = 0;

    int count;

    uint8_t zero_run = 0;

    const uint8_t *start = src;

    uint8_t mask1 = -(esc_count < 2);

    uint8_t mask2 = -(esc_count < 3);

    uint8_t *end = dst + (width - 2);

output_zeros:

    if (l->zeros_rem) {

        count = FFMIN(l->zeros_rem, width - i);

        memset(dst, 0, count);

        l->zeros_rem -= count;

        dst += count;

    }

    while (dst < end) {

        i = 0;

        while (!zero_run && dst + i < end) {

            i++;

            zero_run =

                !(src[i] | (src[i + 1] & mask1) | (src[i + 2] & mask2));

        }

        if (zero_run) {

            zero_run = 0;

            i += esc_count;

            memcpy(dst, src, i);

            dst += i;

            l->zeros_rem = lag_calc_zero_run(src[i]);

            src += i + 1;

            goto output_zeros;

        } else {

            memcpy(dst, src, i);

            src += i;

        }

    }

    return start - src;

}

static int lag_decode_arith_plane(LagarithContext *l, uint8_t *dst,

                                  int width, int height, int stride,

                                  const uint8_t *src, int src_size)

{

    int i = 0;

    int read = 0;

    uint32_t length;

    uint32_t offset = 1;

    int esc_count = src[0];

    GetBitContext gb;

    lag_rac rac;

    rac.avctx = l->avctx;

    l->zeros = 0;

    if (esc_count < 4) {

        length = width * height;

        if (esc_count && AV_RL32(src + 1) < length) {

            length = AV_RL32(src + 1);

            offset += 4;

        }

        init_get_bits(&gb, src + offset, src_size * 8);

        if (lag_read_prob_header(&rac, &gb) < 0)

            return -1;

        lag_rac_init(&rac, &gb, length - stride);

        for (i = 0; i < height; i++)

            read += lag_decode_line(l, &rac, dst + (i * stride), width,

                                    stride, esc_count);

        if (read > length)

            av_log(l->avctx, AV_LOG_WARNING,

                   "Output more bytes than length (%d of %d)\n", read,

                   length);

    } else if (esc_count < 8) {

        esc_count -= 4;

        if (esc_count > 0) {

            /* Zero run coding only, no range coding. */

            for (i = 0; i < height; i++)

                src += lag_decode_zero_run_line(l, dst + (i * stride), src,

                                                width, esc_count);

        } else {

            /* Plane is stored uncompressed */

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

                memcpy(dst + (i * stride), src, width);

                src += width;

            }

        }

    } else if (esc_count == 0xff) {

        /* Plane is a solid run of given value */

        for (i = 0; i < height; i++)

            memset(dst + i * stride, src[1], width);

        /* Do not apply prediction.

           Note: memset to 0 above, setting first value to src[1]

           and applying prediction gives the same result. */

        return 0;

    } else {

        av_log(l->avctx, AV_LOG_ERROR,

               "Invalid zero run escape code! (%#x)\n", esc_count);

        return -1;

    }

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

        lag_pred_line(l, dst, width, stride, i);

        dst += stride;

    }

    return 0;

}

/**

 * Decode a frame.

 * @param avctx codec context

 * @param data output AVFrame

 * @param data_size size of output data or 0 if no picture is returned

 * @param avpkt input packet

 * @return number of consumed bytes on success or negative if decode fails

 */

static int lag_decode_frame(AVCodecContext *avctx,

                            void *data, int *data_size, AVPacket *avpkt)

{

    const uint8_t *buf = avpkt->data;

    int buf_size = avpkt->size;

    LagarithContext *l = avctx->priv_data;

    AVFrame *const p = &l->picture;

    uint8_t frametype = 0;

    uint32_t offset_gu = 0, offset_bv = 0, offset_ry = 9;

    AVFrame *picture = data;

    if (p->data[0])

        avctx->release_buffer(avctx, p);

    p->reference = 0;

    p->key_frame = 1;

    frametype = buf[0];

    offset_gu = AV_RL32(buf + 1);

    offset_bv = AV_RL32(buf + 5);

    switch (frametype) {

    case FRAME_ARITH_YV12:

        avctx->pix_fmt = PIX_FMT_YUV420P;

        if (avctx->get_buffer(avctx, p) < 0) {

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

            return -1;

        }

        lag_decode_arith_plane(l, p->data[0], avctx->width, avctx->height,

                               p->linesize[0], buf + offset_ry,

                               buf_size);

        lag_decode_arith_plane(l, p->data[2], avctx->width / 2,

                               avctx->height / 2, p->linesize[2],

                               buf + offset_gu, buf_size);

        lag_decode_arith_plane(l, p->data[1], avctx->width / 2,

                               avctx->height / 2, p->linesize[1],

                               buf + offset_bv, buf_size);

        break;

    default:

        av_log(avctx, AV_LOG_ERROR,

               "Unsupported Lagarith frame type: %#x\n", frametype);

        return -1;

    }

    *picture = *p;

    *data_size = sizeof(AVFrame);

    return buf_size;

}

static av_cold int lag_decode_init(AVCodecContext *avctx)

{

    LagarithContext *l = avctx->priv_data;

    l->avctx = avctx;

    dsputil_init(&l->dsp, avctx);

    return 0;

}

static av_cold int lag_decode_end(AVCodecContext *avctx)

{

    LagarithContext *l = avctx->priv_data;

    if (l->picture.data[0])

        avctx->release_buffer(avctx, &l->picture);

    return 0;

}

AVCodec lagarith_decoder = {

    "lagarith",

    CODEC_TYPE_VIDEO,

    CODEC_ID_LAGARITH,

    sizeof(LagarithContext),

    lag_decode_init,

    NULL,

    lag_decode_end,

    lag_decode_frame,

    CODEC_CAP_DR1,

    .long_name = NULL_IF_CONFIG_SMALL("Lagarith lossless"),

};