2 * Id Quake II CIN Video Decoder
3 * Copyright (C) 2003 the ffmpeg project
5 * This file is part of FFmpeg.
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.
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.
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
25 * Id Quake II Cin Video Decoder by Dr. Tim Ferguson
26 * For more information about the Id CIN format, visit:
27 * http://www.csse.monash.edu.au/~timf/
29 * This video decoder outputs PAL8 colorspace data. Interacting with this
30 * decoder is a little involved. During initialization, the demuxer must
31 * transmit the 65536-byte Huffman table(s) to the decoder via extradata.
32 * Then, whenever a palette change is encountered while demuxing the file,
33 * the demuxer must use the same extradata space to transmit an
34 * AVPaletteControl structure.
36 * Id CIN video is purely Huffman-coded, intraframe-only codec. It achieves
37 * a little more compression by exploiting the fact that adjacent pixels
40 * Note that this decoder could use ffmpeg's optimized VLC facilities
41 * rather than naive, tree-based Huffman decoding. However, there are 256
42 * Huffman tables. Plus, the VLC bit coding order is right -> left instead
43 * or left -> right, so all of the bits would have to be reversed. Further,
44 * the original Quake II implementation likely used a similar naive
45 * decoding algorithm and it worked fine on much lower spec machines.
57 #define HUFFMAN_TABLE_SIZE 64 * 1024
58 #define HUF_TOKENS 256
59 #define PALETTE_COUNT 256
68 typedef struct IdcinContext {
70 AVCodecContext *avctx;
77 hnode_t huff_nodes[256][HUF_TOKENS*2];
78 int num_huff_nodes[256];
83 * Find the lowest probability node in a Huffman table, and mark it as
84 * being assigned to a higher probability.
85 * Returns the node index of the lowest unused node, or -1 if all nodes
88 static int huff_smallest_node(hnode_t *hnodes, int num_hnodes) {
94 for(i = 0; i < num_hnodes; i++) {
99 if(hnodes[i].count < best) {
100 best = hnodes[i].count;
107 hnodes[best_node].used = 1;
112 * Build the Huffman tree using the generated/loaded probabilities histogram.
115 * huff_nodes[prev][i < HUF_TOKENS] - are the nodes at the base of the tree.
116 * huff_nodes[prev][i >= HUF_TOKENS] - are used to construct the tree.
117 * num_huff_nodes[prev] - contains the index to the root node of the tree.
118 * That is: huff_nodes[prev][num_huff_nodes[prev]] is the root node.
120 static void huff_build_tree(IdcinContext *s, int prev) {
121 hnode_t *node, *hnodes;
124 num_hnodes = HUF_TOKENS;
125 hnodes = s->huff_nodes[prev];
126 for(i = 0; i < HUF_TOKENS * 2; i++)
130 node = &hnodes[num_hnodes]; /* next free node */
132 /* pick two lowest counts */
133 node->children[0] = huff_smallest_node(hnodes, num_hnodes);
134 if(node->children[0] == -1)
135 break; /* reached the root node */
137 node->children[1] = huff_smallest_node(hnodes, num_hnodes);
138 if(node->children[1] == -1)
139 break; /* reached the root node */
141 /* combine nodes probability for new node */
142 node->count = hnodes[node->children[0]].count +
143 hnodes[node->children[1]].count;
147 s->num_huff_nodes[prev] = num_hnodes - 1;
150 static int idcin_decode_init(AVCodecContext *avctx)
152 IdcinContext *s = (IdcinContext *)avctx->priv_data;
153 int i, j, histogram_index = 0;
154 unsigned char *histograms;
157 avctx->pix_fmt = PIX_FMT_PAL8;
158 dsputil_init(&s->dsp, avctx);
160 /* make sure the Huffman tables make it */
161 if (s->avctx->extradata_size != HUFFMAN_TABLE_SIZE) {
162 av_log(s->avctx, AV_LOG_ERROR, " Id CIN video: expected extradata size of %d\n", HUFFMAN_TABLE_SIZE);
166 /* build the 256 Huffman decode trees */
167 histograms = (unsigned char *)s->avctx->extradata;
168 for (i = 0; i < 256; i++) {
169 for(j = 0; j < HUF_TOKENS; j++)
170 s->huff_nodes[i][j].count = histograms[histogram_index++];
171 huff_build_tree(s, i);
174 s->frame.data[0] = NULL;
179 static void idcin_decode_vlcs(IdcinContext *s)
185 int bit_pos, node_num, dat_pos;
187 prev = bit_pos = dat_pos = 0;
188 for (y = 0; y < (s->frame.linesize[0] * s->avctx->height);
189 y += s->frame.linesize[0]) {
190 for (x = y; x < y + s->avctx->width; x++) {
191 node_num = s->num_huff_nodes[prev];
192 hnodes = s->huff_nodes[prev];
194 while(node_num >= HUF_TOKENS) {
196 if(dat_pos >= s->size) {
197 av_log(s->avctx, AV_LOG_ERROR, "Huffman decode error.\n");
201 v = s->buf[dat_pos++];
204 node_num = hnodes[node_num].children[v & 0x01];
209 s->frame.data[0][x] = node_num;
215 static int idcin_decode_frame(AVCodecContext *avctx,
216 void *data, int *data_size,
217 uint8_t *buf, int buf_size)
219 IdcinContext *s = (IdcinContext *)avctx->priv_data;
220 AVPaletteControl *palette_control = avctx->palctrl;
225 if (s->frame.data[0])
226 avctx->release_buffer(avctx, &s->frame);
228 if (avctx->get_buffer(avctx, &s->frame)) {
229 av_log(avctx, AV_LOG_ERROR, " Id CIN Video: get_buffer() failed\n");
233 idcin_decode_vlcs(s);
235 /* make the palette available on the way out */
236 memcpy(s->frame.data[1], palette_control->palette, PALETTE_COUNT * 4);
237 /* If palette changed inform application*/
238 if (palette_control->palette_changed) {
239 palette_control->palette_changed = 0;
240 s->frame.palette_has_changed = 1;
243 *data_size = sizeof(AVFrame);
244 *(AVFrame*)data = s->frame;
246 /* report that the buffer was completely consumed */
250 static int idcin_decode_end(AVCodecContext *avctx)
252 IdcinContext *s = (IdcinContext *)avctx->priv_data;
254 if (s->frame.data[0])
255 avctx->release_buffer(avctx, &s->frame);
260 AVCodec idcin_decoder = {
264 sizeof(IdcinContext),