vp6.c

mediastreamer2是开源的网络传输媒体流的库

/**
 * @file vp6.c
 * VP6 compatible video decoder
 *
 * Copyright (C) 2006  Aurelien Jacobs <[e-mail]>
 *
 * The VP6F decoder accepts an optional 1 byte extradata. It is composed of:
 *  - upper 4bits: difference between encoded width and visible width
 *  - lower 4bits: difference between encoded height and visible height
 *
 * 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
 */

#include <stdlib.h>

#include "avcodec.h"
#include "dsputil.h"
#include "bitstream.h"
#include "huffman.h"
#include "mpegvideo.h"

#include "vp56.h"
#include "vp56data.h"
#include "vp6data.h"


static void vp6_parse_coeff(vp56_context_t *s);
static void vp6_parse_coeff_huffman(vp56_context_t *s);

static int vp6_parse_header(vp56_context_t *s, const uint8_t *buf, int buf_size,
                            int *golden_frame)
{
    vp56_range_coder_t *c = &s->c;
    int parse_filter_info = 0;
    int coeff_offset = 0;
    int vrt_shift = 0;
    int sub_version;
    int rows, cols;
    int res = 1;
    int separated_coeff = buf[0] & 1;

    s->framep[VP56_FRAME_CURRENT]->key_frame = !(buf[0] & 0x80);
    vp56_init_dequant(s, (buf[0] >> 1) & 0x3F);

    if (s->framep[VP56_FRAME_CURRENT]->key_frame) {
        sub_version = buf[1] >> 3;
        if (sub_version > 8)
            return 0;
        s->filter_header = buf[1] & 0x06;
        if (buf[1] & 1) {
            av_log(s->avctx, AV_LOG_ERROR, "interlacing not supported\n");
            return 0;
        }
        if (separated_coeff || !s->filter_header) {
            coeff_offset = AV_RB16(buf+2) - 2;
            buf += 2;
            buf_size -= 2;
        }

        rows = buf[2];  /* number of stored macroblock rows */
        cols = buf[3];  /* number of stored macroblock cols */
        /* buf[4] is number of displayed macroblock rows */
        /* buf[5] is number of displayed macroblock cols */

        if (16*cols != s->avctx->coded_width ||
            16*rows != s->avctx->coded_height) {
            avcodec_set_dimensions(s->avctx, 16*cols, 16*rows);
            if (s->avctx->extradata_size == 1) {
                s->avctx->width  -= s->avctx->extradata[0] >> 4;
                s->avctx->height -= s->avctx->extradata[0] & 0x0F;
            }
            res = 2;
        }

        vp56_init_range_decoder(c, buf+6, buf_size-6);
        vp56_rac_gets(c, 2);

        parse_filter_info = s->filter_header;
        if (sub_version < 8)
            vrt_shift = 5;
        s->sub_version = sub_version;
    } else {
        if (!s->sub_version)
            return 0;

        if (separated_coeff || !s->filter_header) {
            coeff_offset = AV_RB16(buf+1) - 2;
            buf += 2;
            buf_size -= 2;
        }
        vp56_init_range_decoder(c, buf+1, buf_size-1);

        *golden_frame = vp56_rac_get(c);
        if (s->filter_header) {
            s->deblock_filtering = vp56_rac_get(c);
            if (s->deblock_filtering)
                vp56_rac_get(c);
            if (s->sub_version > 7)
                parse_filter_info = vp56_rac_get(c);
        }
    }

    if (parse_filter_info) {
        if (vp56_rac_get(c)) {
            s->filter_mode = 2;
            s->sample_variance_threshold = vp56_rac_gets(c, 5) << vrt_shift;
            s->max_vector_length = 2 << vp56_rac_gets(c, 3);
        } else if (vp56_rac_get(c)) {
            s->filter_mode = 1;
        } else {
            s->filter_mode = 0;
        }
        if (s->sub_version > 7)
            s->filter_selection = vp56_rac_gets(c, 4);
        else
            s->filter_selection = 16;
    }

    s->use_huffman = vp56_rac_get(c);

    s->parse_coeff = vp6_parse_coeff;
    if (coeff_offset) {
        buf      += coeff_offset;
        buf_size -= coeff_offset;
        if (s->use_huffman) {
            s->parse_coeff = vp6_parse_coeff_huffman;
            init_get_bits(&s->gb, buf, buf_size<<3);
        } else {
            vp56_init_range_decoder(&s->cc, buf, buf_size);
            s->ccp = &s->cc;
        }
    } else {
        s->ccp = &s->c;
    }

    return res;
}

static void vp6_coeff_order_table_init(vp56_context_t *s)
{
    int i, pos, idx = 1;

    s->modelp->coeff_index_to_pos[0] = 0;
    for (i=0; i<16; i++)
        for (pos=1; pos<64; pos++)
            if (s->modelp->coeff_reorder[pos] == i)
                s->modelp->coeff_index_to_pos[idx++] = pos;
}

static void vp6_default_models_init(vp56_context_t *s)
{
    vp56_model_t *model = s->modelp;

    model->vector_dct[0] = 0xA2;
    model->vector_dct[1] = 0xA4;
    model->vector_sig[0] = 0x80;
    model->vector_sig[1] = 0x80;

    memcpy(model->mb_types_stats, vp56_def_mb_types_stats, sizeof(model->mb_types_stats));
    memcpy(model->vector_fdv, vp6_def_fdv_vector_model, sizeof(model->vector_fdv));
    memcpy(model->vector_pdv, vp6_def_pdv_vector_model, sizeof(model->vector_pdv));
    memcpy(model->coeff_runv, vp6_def_runv_coeff_model, sizeof(model->coeff_runv));
    memcpy(model->coeff_reorder, vp6_def_coeff_reorder, sizeof(model->coeff_reorder));

    vp6_coeff_order_table_init(s);
}

static void vp6_parse_vector_models(vp56_context_t *s)
{
    vp56_range_coder_t *c = &s->c;
    vp56_model_t *model = s->modelp;
    int comp, node;

    for (comp=0; comp<2; comp++) {
        if (vp56_rac_get_prob(c, vp6_sig_dct_pct[comp][0]))
            model->vector_dct[comp] = vp56_rac_gets_nn(c, 7);
        if (vp56_rac_get_prob(c, vp6_sig_dct_pct[comp][1]))
            model->vector_sig[comp] = vp56_rac_gets_nn(c, 7);
    }

    for (comp=0; comp<2; comp++)
        for (node=0; node<7; node++)
            if (vp56_rac_get_prob(c, vp6_pdv_pct[comp][node]))
                model->vector_pdv[comp][node] = vp56_rac_gets_nn(c, 7);

    for (comp=0; comp<2; comp++)
        for (node=0; node<8; node++)
            if (vp56_rac_get_prob(c, vp6_fdv_pct[comp][node]))
                model->vector_fdv[comp][node] = vp56_rac_gets_nn(c, 7);
}

static int vp6_huff_cmp(const void *va, const void *vb)
{
    const Node *a = va, *b = vb;
    return a->count >= b->count;
}

static void vp6_build_huff_tree(vp56_context_t *s, uint8_t coeff_model[],
                                const uint8_t *map, unsigned size, VLC *vlc)
{
    Node nodes[2*size], *tmp = &nodes[size];
    int a, b, i;

    /* first compute probabilities from model */
    tmp[0].count = 256;
    for (i=0; i<size-1; i++) {
        a = tmp[i].count *        coeff_model[i]  >> 8;
        b = tmp[i].count * (255 - coeff_model[i]) >> 8;
        nodes[map[2*i  ]].count = a + !a;
        nodes[map[2*i+1]].count = b + !b;
    }

    /* then build the huffman tree accodring to probabilities */
    ff_huff_build_tree(s->avctx, vlc, size, nodes, vp6_huff_cmp, 1);
}

static void vp6_parse_coeff_models(vp56_context_t *s)
{
    vp56_range_coder_t *c = &s->c;
    vp56_model_t *model = s->modelp;
    int def_prob[11];
    int node, cg, ctx, pos;
    int ct;    /* code type */
    int pt;    /* plane type (0 for Y, 1 for U or V) */

    memset(def_prob, 0x80, sizeof(def_prob));

    for (pt=0; pt<2; pt++)
        for (node=0; node<11; node++)
            if (vp56_rac_get_prob(c, vp6_dccv_pct[pt][node])) {
                def_prob[node] = vp56_rac_gets_nn(c, 7);
                model->coeff_dccv[pt][node] = def_prob[node];
            } else if (s->framep[VP56_FRAME_CURRENT]->key_frame) {
                model->coeff_dccv[pt][node] = def_prob[node];
            }

    if (vp56_rac_get(c)) {
        for (pos=1; pos<64; pos++)
            if (vp56_rac_get_prob(c, vp6_coeff_reorder_pct[pos]))
                model->coeff_reorder[pos] = vp56_rac_gets(c, 4);
        vp6_coeff_order_table_init(s);
    }

    for (cg=0; cg<2; cg++)
        for (node=0; node<14; node++)
            if (vp56_rac_get_prob(c, vp6_runv_pct[cg][node]))
                model->coeff_runv[cg][node] = vp56_rac_gets_nn(c, 7);

    for (ct=0; ct<3; ct++)
        for (pt=0; pt<2; pt++)
            for (cg=0; cg<6; cg++)
                for (node=0; node<11; node++)
                    if (vp56_rac_get_prob(c, vp6_ract_pct[ct][pt][cg][node])) {
                        def_prob[node] = vp56_rac_gets_nn(c, 7);
                        model->coeff_ract[pt][ct][cg][node] = def_prob[node];
                    } else if (s->framep[VP56_FRAME_CURRENT]->key_frame) {
                        model->coeff_ract[pt][ct][cg][node] = def_prob[node];
                    }

    if (s->use_huffman) {
        for (pt=0; pt<2; pt++) {
            vp6_build_huff_tree(s, model->coeff_dccv[pt],
                                vp6_huff_coeff_map, 12, &s->dccv_vlc[pt]);
            vp6_build_huff_tree(s, model->coeff_runv[pt],
                                vp6_huff_run_map, 9, &s->runv_vlc[pt]);
            for (ct=0; ct<3; ct++)
                for (cg = 0; cg < 6; cg++)
                    vp6_build_huff_tree(s, model->coeff_ract[pt][ct][cg],
                                        vp6_huff_coeff_map, 12,
                                        &s->ract_vlc[pt][ct][cg]);
        }
        memset(s->nb_null, 0, sizeof(s->nb_null));
    } else {
    /* coeff_dcct is a linear combination of coeff_dccv */
    for (pt=0; pt<2; pt++)
        for (ctx=0; ctx<3; ctx++)
            for (node=0; node<5; node++)
                model->coeff_dcct[pt][ctx][node] = av_clip(((model->coeff_dccv[pt][node] * vp6_dccv_lc[ctx][node][0] + 128) >> 8) + vp6_dccv_lc[ctx][node][1], 1, 255);
    }
}

static void vp6_parse_vector_adjustment(vp56_context_t *s, vp56_mv_t *vect)
{
    vp56_range_coder_t *c = &s->c;
    vp56_model_t *model = s->modelp;
    int comp;

    *vect = (vp56_mv_t) {0,0};
    if (s->vector_candidate_pos < 2)
        *vect = s->vector_candidate[0];

    for (comp=0; comp<2; comp++) {
        int i, delta = 0;

        if (vp56_rac_get_prob(c, model->vector_dct[comp])) {
            static const uint8_t prob_order[] = {0, 1, 2, 7, 6, 5, 4};
            for (i=0; i<sizeof(prob_order); i++) {
                int j = prob_order[i];
                delta |= vp56_rac_get_prob(c, model->vector_fdv[comp][j])<<j;
            }
            if (delta & 0xF0)
                delta |= vp56_rac_get_prob(c, model->vector_fdv[comp][3])<<3;
            else
                delta |= 8;
        } else {
            delta = vp56_rac_get_tree(c, vp56_pva_tree,
                                      model->vector_pdv[comp]);
        }

        if (delta && vp56_rac_get_prob(c, model->vector_sig[comp]))
            delta = -delta;

        if (!comp)
            vect->x += delta;
        else
            vect->y += delta;
    }
}

/**