FFmpeg/libavcodec/vp56.h

/**
 * @file
 * VP5 and VP6 compatible video decoder (common features)
 *
 * Copyright (C) 2006  Aurelien Jacobs <aurel@gnuage.org>
 *
 * 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
 */

#ifndef AVCODEC_VP56_H
#define AVCODEC_VP56_H

#include "vp56data.h"
#include "dsputil.h"
#include "get_bits.h"
#include "bytestream.h"
#include "cabac.h"
#include "vp56dsp.h"

typedef struct vp56_context VP56Context;
typedef struct vp56_mv VP56mv;

typedef void (*VP56ParseVectorAdjustment)(VP56Context *s,
                                          VP56mv *vect);
typedef void (*VP56Filter)(VP56Context *s, uint8_t *dst, uint8_t *src,
                           int offset1, int offset2, int stride,
                           VP56mv mv, int mask, int select, int luma);
typedef void (*VP56ParseCoeff)(VP56Context *s);
typedef void (*VP56DefaultModelsInit)(VP56Context *s);
typedef void (*VP56ParseVectorModels)(VP56Context *s);
typedef void (*VP56ParseCoeffModels)(VP56Context *s);
typedef int  (*VP56ParseHeader)(VP56Context *s, const uint8_t *buf,
                                int buf_size, int *golden_frame);

typedef struct {
    int high;
    int bits; /* Stored negated (i.e. negative "bits" is a positive number of bits left)
               * in order to eliminate a negate in cache refilling */
    const uint8_t *buffer;
    const uint8_t *end;
    unsigned long code_word;
} VP56RangeCoder;

typedef struct {
    uint8_t not_null_dc;
    VP56Frame ref_frame;
    DCTELEM dc_coeff;
} VP56RefDc;

struct vp56_mv {
    int x;
    int y;
};

typedef struct {
    uint8_t type;
    VP56mv mv;
} VP56Macroblock;

typedef struct {
    uint8_t coeff_reorder[64];       /* used in vp6 only */
    uint8_t coeff_index_to_pos[64];  /* used in vp6 only */
    uint8_t vector_sig[2];           /* delta sign */
    uint8_t vector_dct[2];           /* delta coding types */
    uint8_t vector_pdi[2][2];        /* predefined delta init */
    uint8_t vector_pdv[2][7];        /* predefined delta values */
    uint8_t vector_fdv[2][8];        /* 8 bit delta value definition */
    uint8_t coeff_dccv[2][11];       /* DC coeff value */
    uint8_t coeff_ract[2][3][6][11]; /* Run/AC coding type and AC coeff value */
    uint8_t coeff_acct[2][3][3][6][5];/* vp5 only AC coding type for coding group < 3 */
    uint8_t coeff_dcct[2][36][5];    /* DC coeff coding type */
    uint8_t coeff_runv[2][14];       /* run value (vp6 only) */
    uint8_t mb_type[3][10][10];      /* model for decoding MB type */
    uint8_t mb_types_stats[3][10][2];/* contextual, next MB type stats */
} VP56Model;

struct vp56_context {
    AVCodecContext *avctx;
    DSPContext dsp;
    VP56DSPContext vp56dsp;
    ScanTable scantable;
    AVFrame frames[4];
    AVFrame *framep[6];
    uint8_t *edge_emu_buffer_alloc;
    uint8_t *edge_emu_buffer;
    VP56RangeCoder c;
    VP56RangeCoder cc;
    VP56RangeCoder *ccp;
    int sub_version;

    /* frame info */
    int plane_width[4];
    int plane_height[4];
    int mb_width;   /* number of horizontal MB */
    int mb_height;  /* number of vertical MB */
    int block_offset[6];

    int quantizer;
    uint16_t dequant_dc;
    uint16_t dequant_ac;
    int8_t *qscale_table;

    /* DC predictors management */
    VP56RefDc *above_blocks;
    VP56RefDc left_block[4];
    int above_block_idx[6];
    DCTELEM prev_dc[3][3];    /* [plan][ref_frame] */

    /* blocks / macroblock */
    VP56mb mb_type;
    VP56Macroblock *macroblocks;
    DECLARE_ALIGNED(16, DCTELEM, block_coeff)[6][64];

    /* motion vectors */
    VP56mv mv[6];  /* vectors for each block in MB */
    VP56mv vector_candidate[2];
    int vector_candidate_pos;

    /* filtering hints */
    int filter_header;               /* used in vp6 only */
    int deblock_filtering;
    int filter_selection;
    int filter_mode;
    int max_vector_length;
    int sample_variance_threshold;

    uint8_t coeff_ctx[4][64];              /* used in vp5 only */
    uint8_t coeff_ctx_last[4];             /* used in vp5 only */

    int has_alpha;

    /* upside-down flipping hints */
    int flip;  /* are we flipping ? */
    int frbi;  /* first row block index in MB */
    int srbi;  /* second row block index in MB */
    int stride[4];  /* stride for each plan */

    const uint8_t *vp56_coord_div;
    VP56ParseVectorAdjustment parse_vector_adjustment;
    VP56Filter filter;
    VP56ParseCoeff parse_coeff;
    VP56DefaultModelsInit default_models_init;
    VP56ParseVectorModels parse_vector_models;
    VP56ParseCoeffModels parse_coeff_models;
    VP56ParseHeader parse_header;

    VP56Model *modelp;
    VP56Model models[2];

    /* huffman decoding */
    int use_huffman;
    GetBitContext gb;
    VLC dccv_vlc[2];
    VLC runv_vlc[2];
    VLC ract_vlc[2][3][6];
    unsigned int nb_null[2][2];       /* number of consecutive NULL DC/AC */
};


void vp56_init(AVCodecContext *avctx, int flip, int has_alpha);
int vp56_free(AVCodecContext *avctx);
void vp56_init_dequant(VP56Context *s, int quantizer);
int vp56_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
                      AVPacket *avpkt);


/**
 * vp56 specific range coder implementation
 */

static inline void vp56_init_range_decoder(VP56RangeCoder *c,
                                           const uint8_t *buf, int buf_size)
{
    c->high = 255;
    c->bits = -8;
    c->buffer = buf;
    c->end = buf + buf_size;
    c->code_word = bytestream_get_be16(&c->buffer);
}

static inline int vp56_rac_get_prob(VP56RangeCoder *c, uint8_t prob)
{
    /* Don't put c->high in a local variable; if we do that, gcc gets
     * the stupids and turns the code below into a branch again. */
    int bits = c->bits;
    unsigned long code_word = c->code_word;
    unsigned int low = 1 + (((c->high - 1) * prob) >> 8);
    unsigned int low_shift = low << 8;
    int bit = code_word >= low_shift;
    int shift;

    /* Incantation to convince GCC to turn these into conditional moves
     * instead of branches -- faster, as this branch is basically
     * unpredictable. */
    c->high = bit ? c->high - low : low;
    code_word = bit ? code_word - low_shift : code_word;

    /* normalize */
    shift = ff_h264_norm_shift[c->high] - 1;
    c->high   <<= shift;
    code_word <<= shift;
    bits       += shift;
    if(bits >= 0 && c->buffer < c->end) {
        code_word |= *c->buffer++ << bits;
        bits -= 8;
    }
    c->bits = bits;
    c->code_word = code_word;
    return bit;
}

static inline int vp56_rac_get(VP56RangeCoder *c)
{
    /* equiprobable */
    int low = (c->high + 1) >> 1;
    unsigned int low_shift = low << 8;
    int bit = c->code_word >= low_shift;
    if (bit) {
        c->high = (c->high - low) << 1;
        c->code_word -= low_shift;
    } else {
        c->high = low << 1;
    }

    /* normalize */
    c->code_word <<= 1;
    if (++c->bits == 0 && c->buffer < c->end) {
        c->bits = -8;
        c->code_word |= *c->buffer++;
    }
    return bit;
}

// rounding is different than vp56_rac_get, is vp56_rac_get wrong?
static inline int vp8_rac_get(VP56RangeCoder *c)
{
    return vp56_rac_get_prob(c, 128);
}

static inline int vp56_rac_gets(VP56RangeCoder *c, int bits)
{
    int value = 0;

    while (bits--) {
        value = (value << 1) | vp56_rac_get(c);
    }

    return value;
}

static inline int vp8_rac_get_uint(VP56RangeCoder *c, int bits)
{
    int value = 0;

    while (bits--) {
        value = (value << 1) | vp8_rac_get(c);
    }

    return value;
}

// fixme: add 1 bit to all the calls to this?
static inline int vp8_rac_get_sint(VP56RangeCoder *c, int bits)
{
    int v;

    if (!vp8_rac_get(c))
        return 0;

    v = vp8_rac_get_uint(c, bits);

    if (vp8_rac_get(c))
        v = -v;

    return v;
}

// P(7)
static inline int vp56_rac_gets_nn(VP56RangeCoder *c, int bits)
{
    int v = vp56_rac_gets(c, 7) << 1;
    return v + !v;
}

static inline int vp8_rac_get_nn(VP56RangeCoder *c)
{
    int v = vp8_rac_get_uint(c, 7) << 1;
    return v + !v;
}

static inline int vp56_rac_get_tree(VP56RangeCoder *c,
                                    const VP56Tree *tree,
                                    const uint8_t *probs)
{
    while (tree->val > 0) {
        if (vp56_rac_get_prob(c, probs[tree->prob_idx]))
            tree += tree->val;
        else
            tree++;
    }
    return -tree->val;
}

/**
 * This is identical to vp8_rac_get_tree except for the possibility of starting
 * on a node other than the root node, needed for coeff decode where this is
 * used to save a bit after a 0 token (by disallowing EOB to immediately follow.)
 */
static inline int vp8_rac_get_tree_with_offset(VP56RangeCoder *c, const int8_t (*tree)[2],
                                               const uint8_t *probs, int i)
{
    do {
        i = tree[i][vp56_rac_get_prob(c, probs[i])];
    } while (i > 0);

    return -i;
}

// how probabilities are associated with decisions is different I think
// well, the new scheme fits in the old but this way has one fewer branches per decision
static inline int vp8_rac_get_tree(VP56RangeCoder *c, const int8_t (*tree)[2],
                                   const uint8_t *probs)
{
    return vp8_rac_get_tree_with_offset(c, tree, probs, 0);
}

// DCTextra
static inline int vp8_rac_get_coeff(VP56RangeCoder *c, const uint8_t *prob)
{
    int v = 0;

    do {
        v = (v<<1) + vp56_rac_get_prob(c, *prob++);
    } while (*prob);

    return v;
}

#endif /* AVCODEC_VP56_H */