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.
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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
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/
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.
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
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.
53 #define HUFFMAN_TABLE_SIZE 64 * 1024
54 #define HUF_TOKENS 256
55 #define PALETTE_COUNT 256
64 typedef struct IdcinContext {
66 AVCodecContext *avctx;
69 const unsigned char *buf;
72 hnode huff_nodes[256][HUF_TOKENS*2];
73 int num_huff_nodes[256];
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
83 static int huff_smallest_node(hnode *hnodes, int num_hnodes) {
89 for(i = 0; i < num_hnodes; i++) {
94 if(hnodes[i].count < best) {
95 best = hnodes[i].count;
102 hnodes[best_node].used = 1;
107 * Build the Huffman tree using the generated/loaded probabilities histogram.
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.
115 static av_cold void huff_build_tree(IdcinContext *s, int prev) {
116 hnode *node, *hnodes;
119 num_hnodes = HUF_TOKENS;
120 hnodes = s->huff_nodes[prev];
121 for(i = 0; i < HUF_TOKENS * 2; i++)
125 node = &hnodes[num_hnodes]; /* next free node */
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 */
132 node->children[1] = huff_smallest_node(hnodes, num_hnodes);
133 if(node->children[1] == -1)
134 break; /* reached the root node */
136 /* combine nodes probability for new node */
137 node->count = hnodes[node->children[0]].count +
138 hnodes[node->children[1]].count;
142 s->num_huff_nodes[prev] = num_hnodes - 1;
145 static av_cold int idcin_decode_init(AVCodecContext *avctx)
147 IdcinContext *s = avctx->priv_data;
148 int i, j, histogram_index = 0;
149 unsigned char *histograms;
152 avctx->pix_fmt = PIX_FMT_PAL8;
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);
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);
168 s->frame.data[0] = NULL;
173 static void idcin_decode_vlcs(IdcinContext *s)
179 int bit_pos, node_num, dat_pos;
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];
188 while(node_num >= HUF_TOKENS) {
190 if(dat_pos >= s->size) {
191 av_log(s->avctx, AV_LOG_ERROR, "Huffman decode error.\n");
195 v = s->buf[dat_pos++];
198 node_num = hnodes[node_num].children[v & 0x01];
203 s->frame.data[0][x] = node_num;
209 static int idcin_decode_frame(AVCodecContext *avctx,
210 void *data, int *data_size,
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;
221 if (s->frame.data[0])
222 avctx->release_buffer(avctx, &s->frame);
224 if (avctx->get_buffer(avctx, &s->frame)) {
225 av_log(avctx, AV_LOG_ERROR, " id CIN Video: get_buffer() failed\n");
229 idcin_decode_vlcs(s);
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;
239 *data_size = sizeof(AVFrame);
240 *(AVFrame*)data = s->frame;
242 /* report that the buffer was completely consumed */
246 static av_cold int idcin_decode_end(AVCodecContext *avctx)
248 IdcinContext *s = avctx->priv_data;
250 if (s->frame.data[0])
251 avctx->release_buffer(avctx, &s->frame);
256 AVCodec idcin_decoder = {
260 sizeof(IdcinContext),
266 .long_name = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),