smacker.c

ffmpeg源码分析

/*
 * Smacker decoder
 * Copyright (c) 2006 Konstantin Shishkov
 *
 * 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 smacker.c
 * Smacker decoder
 */

/*
 * Based on http://wiki.multimedia.cx/index.php?title=Smacker
 */

#include <stdio.h>
#include <stdlib.h>

#include "common.h"
#include "avcodec.h"

#define ALT_BITSTREAM_READER_LE
#include "bitstream.h"

#define SMKTREE_BITS 9
#define SMK_NODE 0x80000000

/*
 * Decoder context
 */
typedef struct SmackVContext {
    AVCodecContext *avctx;
    AVFrame pic;

    int *mmap_tbl, *mclr_tbl, *full_tbl, *type_tbl;
    int mmap_last[3], mclr_last[3], full_last[3], type_last[3];
} SmackVContext;

/**
 * Context used for code reconstructing
 */
typedef struct HuffContext {
    int length;
    int maxlength;
    int current;
    uint32_t *bits;
    int *lengths;
    int *values;
} HuffContext;

/* common parameters used for decode_bigtree */
typedef struct DBCtx {
    VLC *v1, *v2;
    int *recode1, *recode2;
    int escapes[3];
    int *last;
    int lcur;
} DBCtx;

/* possible runs of blocks */
static const int block_runs[64] = {
      1,    2,    3,    4,    5,    6,    7,    8,
      9,   10,   11,   12,   13,   14,   15,   16,
     17,   18,   19,   20,   21,   22,   23,   24,
     25,   26,   27,   28,   29,   30,   31,   32,
     33,   34,   35,   36,   37,   38,   39,   40,
     41,   42,   43,   44,   45,   46,   47,   48,
     49,   50,   51,   52,   53,   54,   55,   56,
     57,   58,   59,  128,  256,  512, 1024, 2048 };

enum SmkBlockTypes {
    SMK_BLK_MONO = 0,
    SMK_BLK_FULL = 1,
    SMK_BLK_SKIP = 2,
    SMK_BLK_FILL = 3 };

/**
 * Decode local frame tree
 */
static int smacker_decode_tree(GetBitContext *gb, HuffContext *hc, uint32_t prefix, int length)
{
    if(!get_bits1(gb)){ //Leaf
        if(hc->current >= 256){
            av_log(NULL, AV_LOG_ERROR, "Tree size exceeded!\n");
            return -1;
        }
        if(length){
            hc->bits[hc->current] = prefix;
            hc->lengths[hc->current] = length;
        } else {
            hc->bits[hc->current] = 0;
            hc->lengths[hc->current] = 0;
        }
        hc->values[hc->current] = get_bits(gb, 8);
        hc->current++;
        if(hc->maxlength < length)
            hc->maxlength = length;
        return 0;
    } else { //Node
        int r;
        length++;
        r = smacker_decode_tree(gb, hc, prefix, length);
        if(r)
            return r;
        return smacker_decode_tree(gb, hc, prefix | (1 << (length - 1)), length);
    }
}

/**
 * Decode header tree
 */
static int smacker_decode_bigtree(GetBitContext *gb, HuffContext *hc, DBCtx *ctx)
{
    if(!get_bits1(gb)){ //Leaf
        int val, i1, i2, b1, b2;
        if(hc->current >= hc->length){
            av_log(NULL, AV_LOG_ERROR, "Tree size exceeded!\n");
            return -1;
        }
        b1 = get_bits_count(gb);
        i1 = get_vlc2(gb, ctx->v1->table, SMKTREE_BITS, 3);
        b1 = get_bits_count(gb) - b1;
        b2 = get_bits_count(gb);
        i2 = get_vlc2(gb, ctx->v2->table, SMKTREE_BITS, 3);
        b2 = get_bits_count(gb) - b2;
        val = ctx->recode1[i1] | (ctx->recode2[i2] << 8);
        if(val == ctx->escapes[0]) {
            ctx->last[0] = hc->current;
            val = 0;
        } else if(val == ctx->escapes[1]) {
            ctx->last[1] = hc->current;
            val = 0;
        } else if(val == ctx->escapes[2]) {
            ctx->last[2] = hc->current;
            val = 0;
        }

        hc->values[hc->current++] = val;
        return 1;
    } else { //Node
        int r = 0, t;

        t = hc->current++;
        r = smacker_decode_bigtree(gb, hc, ctx);
        if(r < 0)
            return r;
        hc->values[t] = SMK_NODE | r;
        r++;
        r += smacker_decode_bigtree(gb, hc, ctx);
        return r;
    }
}

/**
 * Store large tree as FFmpeg's vlc codes
 */
static int smacker_decode_header_tree(SmackVContext *smk, GetBitContext *gb, int **recodes, int *last, int size)
{
    int res;
    HuffContext huff;
    HuffContext tmp1, tmp2;
    VLC vlc[2];
    int escapes[3];
    DBCtx ctx;

    tmp1.length = 256;
    tmp1.maxlength = 0;
    tmp1.current = 0;
    tmp1.bits = av_mallocz(256 * 4);
    tmp1.lengths = av_mallocz(256 * sizeof(int));
    tmp1.values = av_mallocz(256 * sizeof(int));

    tmp2.length = 256;
    tmp2.maxlength = 0;
    tmp2.current = 0;
    tmp2.bits = av_mallocz(256 * 4);
    tmp2.lengths = av_mallocz(256 * sizeof(int));
    tmp2.values = av_mallocz(256 * sizeof(int));

    memset(&vlc[0], 0, sizeof(VLC));
    memset(&vlc[1], 0, sizeof(VLC));

    if(get_bits1(gb)) {
        smacker_decode_tree(gb, &tmp1, 0, 0);
        get_bits1(gb);
        res = init_vlc(&vlc[0], SMKTREE_BITS, tmp1.length,
                    tmp1.lengths, sizeof(int), sizeof(int),
                    tmp1.bits, sizeof(uint32_t), sizeof(uint32_t), INIT_VLC_LE);
        if(res < 0) {
            av_log(smk->avctx, AV_LOG_ERROR, "Cannot build VLC table\n");
            return -1;
        }
    } else {
        av_log(smk->avctx, AV_LOG_ERROR, "Skipping low bytes tree\n");
    }
    if(get_bits1(gb)){
        smacker_decode_tree(gb, &tmp2, 0, 0);
        get_bits1(gb);
        res = init_vlc(&vlc[1], SMKTREE_BITS, tmp2.length,
                    tmp2.lengths, sizeof(int), sizeof(int),
                    tmp2.bits, sizeof(uint32_t), sizeof(uint32_t), INIT_VLC_LE);
        if(res < 0) {
            av_log(smk->avctx, AV_LOG_ERROR, "Cannot build VLC table\n");
            return -1;
        }
    } else {
        av_log(smk->avctx, AV_LOG_ERROR, "Skipping high bytes tree\n");
    }

    escapes[0]  = get_bits(gb, 8);
    escapes[0] |= get_bits(gb, 8) << 8;
    escapes[1]  = get_bits(gb, 8);
    escapes[1] |= get_bits(gb, 8) << 8;
    escapes[2]  = get_bits(gb, 8);
    escapes[2] |= get_bits(gb, 8) << 8;

    last[0] = last[1] = last[2] = -1;

    ctx.escapes[0] = escapes[0];
    ctx.escapes[1] = escapes[1];
    ctx.escapes[2] = escapes[2];
    ctx.v1 = &vlc[0];
    ctx.v2 = &vlc[1];
    ctx.recode1 = tmp1.values;
    ctx.recode2 = tmp2.values;
    ctx.last = last;

    huff.length = ((size + 3) >> 2) + 3;
    huff.maxlength = 0;
    huff.current = 0;
    huff.values = av_mallocz(huff.length * sizeof(int));

    smacker_decode_bigtree(gb, &huff, &ctx);
    get_bits1(gb);
    if(ctx.last[0] == -1) ctx.last[0] = huff.current++;
    if(ctx.last[1] == -1) ctx.last[1] = huff.current++;
    if(ctx.last[2] == -1) ctx.last[2] = huff.current++;

    *recodes = huff.values;

    if(vlc[0].table)
        free_vlc(&vlc[0]);
    if(vlc[1].table)
        free_vlc(&vlc[1]);
    av_free(tmp1.bits);
    av_free(tmp1.lengths);
    av_free(tmp1.values);
    av_free(tmp2.bits);
    av_free(tmp2.lengths);
    av_free(tmp2.values);

    return 0;
}

static int decode_header_trees(SmackVContext *smk) {
    GetBitContext gb;
    int mmap_size, mclr_size, full_size, type_size;

    mmap_size = LE_32(smk->avctx->extradata);
    mclr_size = LE_32(smk->avctx->extradata + 4);
    full_size = LE_32(smk->avctx->extradata + 8);
    type_size = LE_32(smk->avctx->extradata + 12);

    init_get_bits(&gb, smk->avctx->extradata + 16, (smk->avctx->extradata_size - 16) * 8);

    if(!get_bits1(&gb)) {
        av_log(smk->avctx, AV_LOG_INFO, "Skipping MMAP tree\n");
        smk->mmap_tbl = av_malloc(sizeof(int) * 2);
        smk->mmap_tbl[0] = 0;
        smk->mmap_last[0] = smk->mmap_last[1] = smk->mmap_last[2] = 1;
    } else {
        smacker_decode_header_tree(smk, &gb, &smk->mmap_tbl, smk->mmap_last, mmap_size);
    }
    if(!get_bits(&gb, 1)) {
        av_log(smk->avctx, AV_LOG_INFO, "Skipping MCLR tree\n");
        smk->mclr_tbl = av_malloc(sizeof(int) * 2);
        smk->mclr_tbl[0] = 0;
        smk->mclr_last[0] = smk->mclr_last[1] = smk->mclr_last[2] = 1;
    } else {
        smacker_decode_header_tree(smk, &gb, &smk->mclr_tbl, smk->mclr_last, mclr_size);
    }
    if(!get_bits(&gb, 1)) {
        av_log(smk->avctx, AV_LOG_INFO, "Skipping FULL tree\n");
        smk->full_tbl = av_malloc(sizeof(int) * 2);
        smk->full_tbl[0] = 0;
        smk->full_last[0] = smk->full_last[1] = smk->full_last[2] = 1;
    } else {
        smacker_decode_header_tree(smk, &gb, &smk->full_tbl, smk->full_last, full_size);
    }
    if(!get_bits(&gb, 1)) {
        av_log(smk->avctx, AV_LOG_INFO, "Skipping TYPE tree\n");
        smk->type_tbl = av_malloc(sizeof(int) * 2);
        smk->type_tbl[0] = 0;
        smk->type_last[0] = smk->type_last[1] = smk->type_last[2] = 1;
    } else {
        smacker_decode_header_tree(smk, &gb, &smk->type_tbl, smk->type_last, type_size);
    }

    return 0;
}

static always_inline void last_reset(int *recode, int *last) {
    recode[last[0]] = recode[last[1]] = recode[last[2]] = 0;
}

/* get code and update history */
static always_inline int smk_get_code(GetBitContext *gb, int *recode, int *last) {
    register int *table = recode;
    int v, b;

    b = get_bits_count(gb);
    while(*table & SMK_NODE) {
        if(get_bits1(gb))
            table += (*table) & (~SMK_NODE);
        table++;
    }
    v = *table;
    b = get_bits_count(gb) - b;

    if(v != recode[last[0]]) {
        recode[last[2]] = recode[last[1]];
        recode[last[1]] = recode[last[0]];
        recode[last[0]] = v;
    }
    return v;
}

static int decode_frame(AVCodecContext *avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
{
    SmackVContext * const smk = (SmackVContext *)avctx->priv_data;
    uint8_t *out;
    uint32_t *pal;
    GetBitContext gb;
    int blocks, blk, bw, bh;
    int i;
    int stride;

    if(buf_size == 769)
        return 0;
    if(smk->pic.data[0])
            avctx->release_buffer(avctx, &smk->pic);

    smk->pic.reference = 1;
    smk->pic.buffer_hints = FF_BUFFER_HINTS_VALID | FF_BUFFER_HINTS_PRESERVE | FF_BUFFER_HINTS_REUSABLE;
    if(avctx->reget_buffer(avctx, &smk->pic) < 0){
        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
        return -1;