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 58typedef struct 59{ 60 int count; 61 unsigned char used; 62 int children[2]; 63} hnode; 64 65typedef 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 */ 84static 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 */ 116static 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 146static 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 174static 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 210static 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 245static 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 255AVCodec 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}; 267 268