Subversion Repositories Kolibri OS

/*

 * id Quake II CIN Video Decoder

 * Copyright (C) 2003 the ffmpeg project

 *

 * 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

 * id Quake II Cin Video Decoder by Dr. Tim Ferguson

 * For more information about the id CIN format, visit:

 *   http://www.csse.monash.edu.au/~timf/

 *

 * This video decoder outputs PAL8 colorspace data. Interacting with this

 * decoder is a little involved. During initialization, the demuxer must

 * transmit the 65536-byte Huffman table(s) to the decoder via extradata.

 * Then, whenever a palette change is encountered while demuxing the file,

 * the demuxer must use the same extradata space to transmit an

 * AVPaletteControl structure.

 *

 * id CIN video is purely Huffman-coded, intraframe-only codec. It achieves

 * a little more compression by exploiting the fact that adjacent pixels

 * tend to be similar.

 *

 * Note that this decoder could use libavcodec's optimized VLC facilities

 * rather than naive, tree-based Huffman decoding. However, there are 256

 * Huffman tables. Plus, the VLC bit coding order is right -> left instead

 * or left -> right, so all of the bits would have to be reversed. Further,

 * the original Quake II implementation likely used a similar naive

 * decoding algorithm and it worked fine on much lower spec machines.

 */

#include 

#include 

#include 

#include "avcodec.h"

#include "internal.h"

#include "libavutil/internal.h"

#define HUFFMAN_TABLE_SIZE 64 * 1024

#define HUF_TOKENS 256

#define PALETTE_COUNT 256

typedef struct

{

  int count;

  unsigned char used;

  int children[2];

} hnode;

typedef struct IdcinContext {

    AVCodecContext *avctx;

    const unsigned char *buf;

    int size;

    hnode huff_nodes[256][HUF_TOKENS*2];

    int num_huff_nodes[256];

    uint32_t pal[256];

} IdcinContext;

/**

 * Find the lowest probability node in a Huffman table, and mark it as

 * being assigned to a higher probability.

 * @return the node index of the lowest unused node, or -1 if all nodes

 * are used.

 */

static int huff_smallest_node(hnode *hnodes, int num_hnodes) {

    int i;

    int best, best_node;

    best = 99999999;

    best_node = -1;

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

        if(hnodes[i].used)

            continue;

        if(!hnodes[i].count)

            continue;

        if(hnodes[i].count < best) {

            best = hnodes[i].count;

            best_node = i;

        }

    }

    if(best_node == -1)

        return -1;

    hnodes[best_node].used = 1;

    return best_node;

}

/*

 * Build the Huffman tree using the generated/loaded probabilities histogram.

 *

 * On completion:

 *  huff_nodes[prev][i < HUF_TOKENS] - are the nodes at the base of the tree.

 *  huff_nodes[prev][i >= HUF_TOKENS] - are used to construct the tree.

 *  num_huff_nodes[prev] - contains the index to the root node of the tree.

 *    That is: huff_nodes[prev][num_huff_nodes[prev]] is the root node.

 */

static av_cold void huff_build_tree(IdcinContext *s, int prev) {

    hnode *node, *hnodes;

     int num_hnodes, i;

    num_hnodes = HUF_TOKENS;

    hnodes = s->huff_nodes[prev];

    for(i = 0; i < HUF_TOKENS * 2; i++)

        hnodes[i].used = 0;

    while (1) {

        node = &hnodes[num_hnodes];             /* next free node */

        /* pick two lowest counts */

        node->children[0] = huff_smallest_node(hnodes, num_hnodes);

        if(node->children[0] == -1)

            break;      /* reached the root node */

        node->children[1] = huff_smallest_node(hnodes, num_hnodes);

        if(node->children[1] == -1)

            break;      /* reached the root node */

        /* combine nodes probability for new node */

        node->count = hnodes[node->children[0]].count +

        hnodes[node->children[1]].count;

        num_hnodes++;

    }

    s->num_huff_nodes[prev] = num_hnodes - 1;

}

static av_cold int idcin_decode_init(AVCodecContext *avctx)

{

    IdcinContext *s = avctx->priv_data;

    int i, j, histogram_index = 0;

    unsigned char *histograms;

    s->avctx = avctx;

    avctx->pix_fmt = AV_PIX_FMT_PAL8;

    /* make sure the Huffman tables make it */

    if (s->avctx->extradata_size != HUFFMAN_TABLE_SIZE) {

        av_log(s->avctx, AV_LOG_ERROR, "  id CIN video: expected extradata size of %d\n", HUFFMAN_TABLE_SIZE);

        return -1;

    }

    /* build the 256 Huffman decode trees */

    histograms = (unsigned char *)s->avctx->extradata;

    for (i = 0; i < 256; i++) {

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

            s->huff_nodes[i][j].count = histograms[histogram_index++];

        huff_build_tree(s, i);

    }

    return 0;

}

static int idcin_decode_vlcs(IdcinContext *s, AVFrame *frame)

{

    hnode *hnodes;

    long x, y;

    int prev;

    unsigned char v = 0;

    int bit_pos, node_num, dat_pos;

    prev = bit_pos = dat_pos = 0;

    for (y = 0; y < (frame->linesize[0] * s->avctx->height);

        y += frame->linesize[0]) {

        for (x = y; x < y + s->avctx->width; x++) {

            node_num = s->num_huff_nodes[prev];

            hnodes = s->huff_nodes[prev];

            while(node_num >= HUF_TOKENS) {

                if(!bit_pos) {

                    if(dat_pos >= s->size) {

                        av_log(s->avctx, AV_LOG_ERROR, "Huffman decode error.\n");

                        return -1;

                    }

                    bit_pos = 8;

                    v = s->buf[dat_pos++];

                }

                node_num = hnodes[node_num].children[v & 0x01];

                v = v >> 1;

                bit_pos--;

            }

            frame->data[0][x] = node_num;

            prev = node_num;

        }

    }

    return 0;

}

static int idcin_decode_frame(AVCodecContext *avctx,

                              void *data, int *got_frame,

                              AVPacket *avpkt)

{

    const uint8_t *buf = avpkt->data;

    int buf_size = avpkt->size;

    IdcinContext *s = avctx->priv_data;

    const uint8_t *pal = av_packet_get_side_data(avpkt, AV_PKT_DATA_PALETTE, NULL);

    AVFrame *frame = data;

    int ret;

    s->buf = buf;

    s->size = buf_size;

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

        return ret;

    if (idcin_decode_vlcs(s, frame))

        return AVERROR_INVALIDDATA;

    if (pal) {

        frame->palette_has_changed = 1;

        memcpy(s->pal, pal, AVPALETTE_SIZE);

    }

    /* make the palette available on the way out */

    memcpy(frame->data[1], s->pal, AVPALETTE_SIZE);

    *got_frame = 1;

    /* report that the buffer was completely consumed */

    return buf_size;

}

AVCodec ff_idcin_decoder = {

    .name           = "idcinvideo",

    .long_name      = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),

    .type           = AVMEDIA_TYPE_VIDEO,

    .id             = AV_CODEC_ID_IDCIN,

    .priv_data_size = sizeof(IdcinContext),

    .init           = idcin_decode_init,

    .decode         = idcin_decode_frame,

    .capabilities   = CODEC_CAP_DR1,

};