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
  51 #include "avcodec.h"
  52
  53 #define HUFFMAN_TABLE_SIZE 64 * 1024
  54 #define HUF_TOKENS 256
  55 #define PALETTE_COUNT 256
  56
  57 typedef struct
  58 {
  59   int count;
  60   unsigned char used;
  61   int children[2];
  62 } hnode;
  63
  64 typedef struct IdcinContext {
  65
  66     AVCodecContext *avctx;
  67     AVFrame frame;
  68
  69     const unsigned char *buf;
  70     int size;
  71
  72     hnode huff_nodes[256][HUF_TOKENS*2];
  73     int num_huff_nodes[256];
  74
  75 } IdcinContext;
  76
  77 /*
  78  * Find the lowest probability node in a Huffman table, and mark it as
  79  * being assigned to a higher probability.
  80  * Returns the node index of the lowest unused node, or -1 if all nodes
  81  * are used.
  82  */
  83 static int huff_smallest_node(hnode *hnodes, int num_hnodes) {
  84     int i;
  85     int best, best_node;
  86
  87     best = 99999999;
  88     best_node = -1;
  89     for(i = 0; i < num_hnodes; i++) {
  90         if(hnodes[i].used)
  91             continue;
  92         if(!hnodes[i].count)
  93             continue;
  94         if(hnodes[i].count < best) {
  95             best = hnodes[i].count;
  96             best_node = i;
  97         }
  98     }
  99
 100     if(best_node == -1)
 101         return -1;
 102     hnodes[best_node].used = 1;
 103     return best_node;
 104 }
 105
 106 /*
 107  * Build the Huffman tree using the generated/loaded probabilities histogram.
 108  *
 109  * On completion:
 110  *  huff_nodes[prev][i < HUF_TOKENS] - are the nodes at the base of the tree.
 111  *  huff_nodes[prev][i >= HUF_TOKENS] - are used to construct the tree.
 112  *  num_huff_nodes[prev] - contains the index to the root node of the tree.
 113  *    That is: huff_nodes[prev][num_huff_nodes[prev]] is the root node.
 114  */
 115 static av_cold void huff_build_tree(IdcinContext *s, int prev) {
 116     hnode *node, *hnodes;
 117      int num_hnodes, i;
 118
 119     num_hnodes = HUF_TOKENS;
 120     hnodes = s->huff_nodes[prev];
 121     for(i = 0; i < HUF_TOKENS * 2; i++)
 122         hnodes[i].used = 0;
 123
 124     while (1) {
 125         node = &hnodes[num_hnodes];             /* next free node */
 126
 127         /* pick two lowest counts */
 128         node->children[0] = huff_smallest_node(hnodes, num_hnodes);
 129         if(node->children[0] == -1)
 130             break;      /* reached the root node */
 131
 132         node->children[1] = huff_smallest_node(hnodes, num_hnodes);
 133         if(node->children[1] == -1)
 134             break;      /* reached the root node */
 135
 136         /* combine nodes probability for new node */
 137         node->count = hnodes[node->children[0]].count +
 138         hnodes[node->children[1]].count;
 139         num_hnodes++;
 140     }
 141
 142     s->num_huff_nodes[prev] = num_hnodes - 1;
 143 }
 144
 145 static av_cold int idcin_decode_init(AVCodecContext *avctx)
 146 {
 147     IdcinContext *s = avctx->priv_data;
 148     int i, j, histogram_index = 0;
 149     unsigned char *histograms;
 150
 151     s->avctx = avctx;
 152     avctx->pix_fmt = PIX_FMT_PAL8;
 153
 154     /* make sure the Huffman tables make it */
 155     if (s->avctx->extradata_size != HUFFMAN_TABLE_SIZE) {
 156         av_log(s->avctx, AV_LOG_ERROR, "  id CIN video: expected extradata size of %d\n", HUFFMAN_TABLE_SIZE);
 157         return -1;
 158     }
 159
 160     /* build the 256 Huffman decode trees */
 161     histograms = (unsigned char *)s->avctx->extradata;
 162     for (i = 0; i < 256; i++) {
 163         for(j = 0; j < HUF_TOKENS; j++)
 164             s->huff_nodes[i][j].count = histograms[histogram_index++];
 165         huff_build_tree(s, i);
 166     }
 167
 168     s->frame.data[0] = NULL;
 169
 170     return 0;
 171 }
 172
 173 static void idcin_decode_vlcs(IdcinContext *s)
 174 {
 175     hnode *hnodes;
 176     long x, y;
 177     int prev;
 178     unsigned char v = 0;
 179     int bit_pos, node_num, dat_pos;
 180
 181     prev = bit_pos = dat_pos = 0;
 182     for (y = 0; y < (s->frame.linesize[0] * s->avctx->height);
 183         y += s->frame.linesize[0]) {
 184         for (x = y; x < y + s->avctx->width; x++) {
 185             node_num = s->num_huff_nodes[prev];
 186             hnodes = s->huff_nodes[prev];
 187
 188             while(node_num >= HUF_TOKENS) {
 189                 if(!bit_pos) {
 190                     if(dat_pos >= s->size) {
 191                         av_log(s->avctx, AV_LOG_ERROR, "Huffman decode error.\n");
 192                         return;
 193                     }
 194                     bit_pos = 8;
 195                     v = s->buf[dat_pos++];
 196                 }
 197
 198                 node_num = hnodes[node_num].children[v & 0x01];
 199                 v = v >> 1;
 200                 bit_pos--;
 201             }
 202
 203             s->frame.data[0][x] = node_num;
 204             prev = node_num;
 205         }
 206     }
 207 }
 208
 209 static int idcin_decode_frame(AVCodecContext *avctx,
 210                               void *data, int *data_size,
 211                               AVPacket *avpkt)
 212 {
 213     const uint8_t *buf = avpkt->data;
 214     int buf_size = avpkt->size;
 215     IdcinContext *s = avctx->priv_data;
 216     AVPaletteControl *palette_control = avctx->palctrl;
 217
 218     s->buf = buf;
 219     s->size = buf_size;
 220
 221     if (s->frame.data[0])
 222         avctx->release_buffer(avctx, &s->frame);
 223
 224     if (avctx->get_buffer(avctx, &s->frame)) {
 225         av_log(avctx, AV_LOG_ERROR, "  id CIN Video: get_buffer() failed\n");
 226         return -1;
 227     }
 228
 229     idcin_decode_vlcs(s);
 230
 231     /* make the palette available on the way out */
 232     memcpy(s->frame.data[1], palette_control->palette, PALETTE_COUNT * 4);
 233     /* If palette changed inform application*/
 234     if (palette_control->palette_changed) {
 235         palette_control->palette_changed = 0;
 236         s->frame.palette_has_changed = 1;
 237     }
 238
 239     *data_size = sizeof(AVFrame);
 240     *(AVFrame*)data = s->frame;
 241
 242     /* report that the buffer was completely consumed */
 243     return buf_size;
 244 }
 245
 246 static av_cold int idcin_decode_end(AVCodecContext *avctx)
 247 {
 248     IdcinContext *s = avctx->priv_data;
 249
 250     if (s->frame.data[0])
 251         avctx->release_buffer(avctx, &s->frame);
 252
 253     return 0;
 254 }
 255
 256 AVCodec idcin_decoder = {
 257     "idcinvideo",
 258     CODEC_TYPE_VIDEO,
 259     CODEC_ID_IDCIN,
 260     sizeof(IdcinContext),
 261     idcin_decode_init,
 262     NULL,
 263     idcin_decode_end,
 264     idcin_decode_frame,
 265     CODEC_CAP_DR1,
 266     .long_name = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),
 267 };
 268