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 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 57typedef struct 58{ 59 int count; 60 unsigned char used; 61 int children[2]; 62} hnode; 63 64typedef 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 */ 83static 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 */ 115static 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 145static 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 173static 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 209static 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 246static 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 256AVCodec idcin_decoder = { 257 "idcinvideo", 258 AVMEDIA_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}; 268 269