2 * Id Quake II CIN Video Decoder
3 * Copyright (C) 2003 the ffmpeg project
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 * Id Quake II Cin Video Decoder by Dr. Tim Ferguson
24 * For more information about the Id CIN format, visit:
25 * http://www.csse.monash.edu.au/~timf/
27 * This video decoder outputs PAL8 colorspace data. Interacting with this
28 * decoder is a little involved. During initialization, the demuxer must
29 * transmit the 65536-byte Huffman table(s) to the decoder via extradata.
30 * Then, whenever a palette change is encountered while demuxing the file,
31 * the demuxer must use the same extradata space to transmit an
32 * AVPaletteControl structure.
34 * Id CIN video is purely Huffman-coded, intraframe-only codec. It achieves
35 * a little more compression by exploiting the fact that adjacent pixels
38 * Note that this decoder could use ffmpeg's optimized VLC facilities
39 * rather than naive, tree-based Huffman decoding. However, there are 256
40 * Huffman tables. Plus, the VLC bit coding order is right -> left instead
41 * or left -> right, so all of the bits would have to be reversed. Further,
42 * the original Quake II implementation likely used a similar naive
43 * decoding algorithm and it worked fine on much lower spec machines.
55 #define HUFFMAN_TABLE_SIZE 64 * 1024
56 #define HUF_TOKENS 256
57 #define PALETTE_COUNT 256
66 typedef struct IdcinContext {
68 AVCodecContext *avctx;
75 hnode_t huff_nodes[256][HUF_TOKENS*2];
76 int num_huff_nodes[256];
81 * Find the lowest probability node in a Huffman table, and mark it as
82 * being assigned to a higher probability.
83 * Returns the node index of the lowest unused node, or -1 if all nodes
86 static int huff_smallest_node(hnode_t *hnodes, int num_hnodes) {
92 for(i = 0; i < num_hnodes; i++) {
97 if(hnodes[i].count < best) {
98 best = hnodes[i].count;
105 hnodes[best_node].used = 1;
110 * Build the Huffman tree using the generated/loaded probabilities histogram.
113 * huff_nodes[prev][i < HUF_TOKENS] - are the nodes at the base of the tree.
114 * huff_nodes[prev][i >= HUF_TOKENS] - are used to construct the tree.
115 * num_huff_nodes[prev] - contains the index to the root node of the tree.
116 * That is: huff_nodes[prev][num_huff_nodes[prev]] is the root node.
118 static void huff_build_tree(IdcinContext *s, int prev) {
119 hnode_t *node, *hnodes;
122 num_hnodes = HUF_TOKENS;
123 hnodes = s->huff_nodes[prev];
124 for(i = 0; i < HUF_TOKENS * 2; i++)
128 node = &hnodes[num_hnodes]; /* next free node */
130 /* pick two lowest counts */
131 node->children[0] = huff_smallest_node(hnodes, num_hnodes);
132 if(node->children[0] == -1)
133 break; /* reached the root node */
135 node->children[1] = huff_smallest_node(hnodes, num_hnodes);
136 if(node->children[1] == -1)
137 break; /* reached the root node */
139 /* combine nodes probability for new node */
140 node->count = hnodes[node->children[0]].count +
141 hnodes[node->children[1]].count;
145 s->num_huff_nodes[prev] = num_hnodes - 1;
148 static int idcin_decode_init(AVCodecContext *avctx)
150 IdcinContext *s = (IdcinContext *)avctx->priv_data;
151 int i, j, histogram_index = 0;
152 unsigned char *histograms;
155 avctx->pix_fmt = PIX_FMT_PAL8;
156 avctx->has_b_frames = 0;
157 dsputil_init(&s->dsp, avctx);
159 /* make sure the Huffman tables make it */
160 if (s->avctx->extradata_size != HUFFMAN_TABLE_SIZE) {
161 av_log(s->avctx, AV_LOG_ERROR, " Id CIN video: expected extradata size of %d\n", HUFFMAN_TABLE_SIZE);
165 /* build the 256 Huffman decode trees */
166 histograms = (unsigned char *)s->avctx->extradata;
167 for (i = 0; i < 256; i++) {
168 for(j = 0; j < HUF_TOKENS; j++)
169 s->huff_nodes[i][j].count = histograms[histogram_index++];
170 huff_build_tree(s, i);
173 s->frame.data[0] = NULL;
178 static void idcin_decode_vlcs(IdcinContext *s)
184 int bit_pos, node_num, dat_pos;
186 prev = bit_pos = dat_pos = 0;
187 for (y = 0; y < (s->frame.linesize[0] * s->avctx->height);
188 y += s->frame.linesize[0]) {
189 for (x = y; x < y + s->avctx->width; x++) {
190 node_num = s->num_huff_nodes[prev];
191 hnodes = s->huff_nodes[prev];
193 while(node_num >= HUF_TOKENS) {
195 if(dat_pos >= s->size) {
196 av_log(s->avctx, AV_LOG_ERROR, "Huffman decode error.\n");
200 v = s->buf[dat_pos++];
203 node_num = hnodes[node_num].children[v & 0x01];
208 s->frame.data[0][x] = node_num;
214 static int idcin_decode_frame(AVCodecContext *avctx,
215 void *data, int *data_size,
216 uint8_t *buf, int buf_size)
218 IdcinContext *s = (IdcinContext *)avctx->priv_data;
219 AVPaletteControl *palette_control = avctx->palctrl;
224 if (s->frame.data[0])
225 avctx->release_buffer(avctx, &s->frame);
227 if (avctx->get_buffer(avctx, &s->frame)) {
228 av_log(avctx, AV_LOG_ERROR, " Id CIN Video: get_buffer() failed\n");
232 idcin_decode_vlcs(s);
234 /* make the palette available on the way out */
235 memcpy(s->frame.data[1], palette_control->palette, PALETTE_COUNT * 4);
236 /* If palette changed inform application*/
237 if (palette_control->palette_changed) {
238 palette_control->palette_changed = 0;
239 s->frame.palette_has_changed = 1;
242 *data_size = sizeof(AVFrame);
243 *(AVFrame*)data = s->frame;
245 /* report that the buffer was completely consumed */
249 static int idcin_decode_end(AVCodecContext *avctx)
251 IdcinContext *s = (IdcinContext *)avctx->priv_data;
253 if (s->frame.data[0])
254 avctx->release_buffer(avctx, &s->frame);
259 AVCodec idcin_decoder = {
263 sizeof(IdcinContext),