libavcodec/idcinvideo.c

   1 /*
   2  * id Quake II CIN Video Decoder
   3  * Copyright (C) 2003 the ffmpeg project
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file libavcodec/idcinvideo.c
  24  * id Quake II Cin Video Decoder by Dr. Tim Ferguson
  25  * For more information about the id CIN format, visit:
  26  *   http://www.csse.monash.edu.au/~timf/
  27  *
  28  * This video decoder outputs PAL8 colorspace data. Interacting with this
  29  * decoder is a little involved. During initialization, the demuxer must
  30  * transmit the 65536-byte Huffman table(s) to the decoder via extradata.
  31  * Then, whenever a palette change is encountered while demuxing the file,
  32  * the demuxer must use the same extradata space to transmit an
  33  * AVPaletteControl structure.
  34  *
  35  * id CIN video is purely Huffman-coded, intraframe-only codec. It achieves
  36  * a little more compression by exploiting the fact that adjacent pixels
  37  * tend to be similar.
  38  *
  39  * Note that this decoder could use ffmpeg's optimized VLC facilities
  40  * rather than naive, tree-based Huffman decoding. However, there are 256
  41  * Huffman tables. Plus, the VLC bit coding order is right -> left instead
  42  * or left -> right, so all of the bits would have to be reversed. Further,
  43  * the original Quake II implementation likely used a similar naive
  44  * decoding algorithm and it worked fine on much lower spec machines.
  45  */
  46
  47 #include <stdio.h>
  48 #include <stdlib.h>
  49 #include <string.h>
  50 #include <unistd.h>
  51
  52 #include "avcodec.h"
  53
  54 #define HUFFMAN_TABLE_SIZE 64 * 1024
  55 #define HUF_TOKENS 256
  56 #define PALETTE_COUNT 256
  57
  58 typedef struct
  59 {
  60   int count;
  61   unsigned char used;
  62   int children[2];
  63 } hnode;
  64
  65 typedef struct IdcinContext {
  66
  67     AVCodecContext *avctx;
  68     AVFrame frame;
  69
  70     const unsigned char *buf;
  71     int size;
  72
  73     hnode huff_nodes[256][HUF_TOKENS*2];
  74     int num_huff_nodes[256];
  75
  76 } IdcinContext;
  77
  78 /*
  79  * Find the lowest probability node in a Huffman table, and mark it as
  80  * being assigned to a higher probability.
  81  * Returns the node index of the lowest unused node, or -1 if all nodes
  82  * are used.
  83  */
  84 static int huff_smallest_node(hnode *hnodes, int num_hnodes) {
  85     int i;
  86     int best, best_node;
  87
  88     best = 99999999;
  89     best_node = -1;
  90     for(i = 0; i < num_hnodes; i++) {
  91         if(hnodes[i].used)
  92             continue;
  93         if(!hnodes[i].count)
  94             continue;
  95         if(hnodes[i].count < best) {
  96             best = hnodes[i].count;
  97             best_node = i;
  98         }
  99     }
 100
 101     if(best_node == -1)
 102         return -1;
 103     hnodes[best_node].used = 1;
 104     return best_node;
 105 }
 106
 107 /*
 108  * Build the Huffman tree using the generated/loaded probabilities histogram.
 109  *
 110  * On completion:
 111  *  huff_nodes[prev][i < HUF_TOKENS] - are the nodes at the base of the tree.
 112  *  huff_nodes[prev][i >= HUF_TOKENS] - are used to construct the tree.
 113  *  num_huff_nodes[prev] - contains the index to the root node of the tree.
 114  *    That is: huff_nodes[prev][num_huff_nodes[prev]] is the root node.
 115  */
 116 static av_cold void huff_build_tree(IdcinContext *s, int prev) {
 117     hnode *node, *hnodes;
 118      int num_hnodes, i;
 119
 120     num_hnodes = HUF_TOKENS;
 121     hnodes = s->huff_nodes[prev];
 122     for(i = 0; i < HUF_TOKENS * 2; i++)
 123         hnodes[i].used = 0;
 124
 125     while (1) {
 126         node = &hnodes[num_hnodes];             /* next free node */
 127
 128         /* pick two lowest counts */
 129         node->children[0] = huff_smallest_node(hnodes, num_hnodes);
 130         if(node->children[0] == -1)
 131             break;      /* reached the root node */
 132
 133         node->children[1] = huff_smallest_node(hnodes, num_hnodes);
 134         if(node->children[1] == -1)
 135             break;      /* reached the root node */
 136
 137         /* combine nodes probability for new node */
 138         node->count = hnodes[node->children[0]].count +
 139         hnodes[node->children[1]].count;
 140         num_hnodes++;
 141     }
 142
 143     s->num_huff_nodes[prev] = num_hnodes - 1;
 144 }
 145
 146 static av_cold int idcin_decode_init(AVCodecContext *avctx)
 147 {
 148     IdcinContext *s = avctx->priv_data;
 149     int i, j, histogram_index = 0;
 150     unsigned char *histograms;
 151
 152     s->avctx = avctx;
 153     avctx->pix_fmt = PIX_FMT_PAL8;
 154
 155     /* make sure the Huffman tables make it */
 156     if (s->avctx->extradata_size != HUFFMAN_TABLE_SIZE) {
 157         av_log(s->avctx, AV_LOG_ERROR, "  id CIN video: expected extradata size of %d\n", HUFFMAN_TABLE_SIZE);
 158         return -1;
 159     }
 160
 161     /* build the 256 Huffman decode trees */
 162     histograms = (unsigned char *)s->avctx->extradata;
 163     for (i = 0; i < 256; i++) {
 164         for(j = 0; j < HUF_TOKENS; j++)
 165             s->huff_nodes[i][j].count = histograms[histogram_index++];
 166         huff_build_tree(s, i);
 167     }
 168
 169     s->frame.data[0] = NULL;
 170
 171     return 0;
 172 }
 173
 174 static void idcin_decode_vlcs(IdcinContext *s)
 175 {
 176     hnode *hnodes;
 177     long x, y;
 178     int prev;
 179     unsigned char v = 0;
 180     int bit_pos, node_num, dat_pos;
 181
 182     prev = bit_pos = dat_pos = 0;
 183     for (y = 0; y < (s->frame.linesize[0] * s->avctx->height);
 184         y += s->frame.linesize[0]) {
 185         for (x = y; x < y + s->avctx->width; x++) {
 186             node_num = s->num_huff_nodes[prev];
 187             hnodes = s->huff_nodes[prev];
 188
 189             while(node_num >= HUF_TOKENS) {
 190                 if(!bit_pos) {
 191                     if(dat_pos >= s->size) {
 192                         av_log(s->avctx, AV_LOG_ERROR, "Huffman decode error.\n");
 193                         return;
 194                     }
 195                     bit_pos = 8;
 196                     v = s->buf[dat_pos++];
 197                 }
 198
 199                 node_num = hnodes[node_num].children[v & 0x01];
 200                 v = v >> 1;
 201                 bit_pos--;
 202             }
 203
 204             s->frame.data[0][x] = node_num;
 205             prev = node_num;
 206         }
 207     }
 208 }
 209
 210 static int idcin_decode_frame(AVCodecContext *avctx,
 211                               void *data, int *data_size,
 212                               const uint8_t *buf, int buf_size)
 213 {
 214     IdcinContext *s = avctx->priv_data;
 215     AVPaletteControl *palette_control = avctx->palctrl;
 216
 217     s->buf = buf;
 218     s->size = buf_size;
 219
 220     if (s->frame.data[0])
 221         avctx->release_buffer(avctx, &s->frame);
 222
 223     if (avctx->get_buffer(avctx, &s->frame)) {
 224         av_log(avctx, AV_LOG_ERROR, "  id CIN Video: get_buffer() failed\n");
 225         return -1;
 226     }
 227
 228     idcin_decode_vlcs(s);
 229
 230     /* make the palette available on the way out */
 231     memcpy(s->frame.data[1], palette_control->palette, PALETTE_COUNT * 4);
 232     /* If palette changed inform application*/
 233     if (palette_control->palette_changed) {
 234         palette_control->palette_changed = 0;
 235         s->frame.palette_has_changed = 1;
 236     }
 237
 238     *data_size = sizeof(AVFrame);
 239     *(AVFrame*)data = s->frame;
 240
 241     /* report that the buffer was completely consumed */
 242     return buf_size;
 243 }
 244
 245 static av_cold int idcin_decode_end(AVCodecContext *avctx)
 246 {
 247     IdcinContext *s = avctx->priv_data;
 248
 249     if (s->frame.data[0])
 250         avctx->release_buffer(avctx, &s->frame);
 251
 252     return 0;
 253 }
 254
 255 AVCodec idcin_decoder = {
 256     "idcinvideo",
 257     CODEC_TYPE_VIDEO,
 258     CODEC_ID_IDCIN,
 259     sizeof(IdcinContext),
 260     idcin_decode_init,
 261     NULL,
 262     idcin_decode_end,
 263     idcin_decode_frame,
 264     CODEC_CAP_DR1,
 265     .long_name = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),
 266 };
 267