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
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 libavcodec'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 #include "libavutil/internal.h"
55 #define HUFFMAN_TABLE_SIZE 64 * 1024
56 #define HUF_TOKENS 256
57 #define PALETTE_COUNT 256
66 typedef struct IdcinContext {
68 AVCodecContext *avctx;
70 const unsigned char *buf;
73 hnode huff_nodes[256][HUF_TOKENS*2];
74 int num_huff_nodes[256];
80 * Find the lowest probability node in a Huffman table, and mark it as
81 * being assigned to a higher probability.
82 * @return the node index of the lowest unused node, or -1 if all nodes
85 static int huff_smallest_node(hnode *hnodes, int num_hnodes) {
91 for(i = 0; i < num_hnodes; i++) {
96 if(hnodes[i].count < best) {
97 best = hnodes[i].count;
104 hnodes[best_node].used = 1;
109 * Build the Huffman tree using the generated/loaded probabilities histogram.
112 * huff_nodes[prev][i < HUF_TOKENS] - are the nodes at the base of the tree.
113 * huff_nodes[prev][i >= HUF_TOKENS] - are used to construct the tree.
114 * num_huff_nodes[prev] - contains the index to the root node of the tree.
115 * That is: huff_nodes[prev][num_huff_nodes[prev]] is the root node.
117 static av_cold void huff_build_tree(IdcinContext *s, int prev) {
118 hnode *node, *hnodes;
121 num_hnodes = HUF_TOKENS;
122 hnodes = s->huff_nodes[prev];
123 for(i = 0; i < HUF_TOKENS * 2; i++)
127 node = &hnodes[num_hnodes]; /* next free node */
129 /* pick two lowest counts */
130 node->children[0] = huff_smallest_node(hnodes, num_hnodes);
131 if(node->children[0] == -1)
132 break; /* reached the root node */
134 node->children[1] = huff_smallest_node(hnodes, num_hnodes);
135 if(node->children[1] == -1)
136 break; /* reached the root node */
138 /* combine nodes probability for new node */
139 node->count = hnodes[node->children[0]].count +
140 hnodes[node->children[1]].count;
144 s->num_huff_nodes[prev] = num_hnodes - 1;
147 static av_cold int idcin_decode_init(AVCodecContext *avctx)
149 IdcinContext *s = avctx->priv_data;
150 int i, j, histogram_index = 0;
151 unsigned char *histograms;
154 avctx->pix_fmt = AV_PIX_FMT_PAL8;
156 /* make sure the Huffman tables make it */
157 if (s->avctx->extradata_size != HUFFMAN_TABLE_SIZE) {
158 av_log(s->avctx, AV_LOG_ERROR, " id CIN video: expected extradata size of %d\n", HUFFMAN_TABLE_SIZE);
162 /* build the 256 Huffman decode trees */
163 histograms = (unsigned char *)s->avctx->extradata;
164 for (i = 0; i < 256; i++) {
165 for(j = 0; j < HUF_TOKENS; j++)
166 s->huff_nodes[i][j].count = histograms[histogram_index++];
167 huff_build_tree(s, i);
173 static int idcin_decode_vlcs(IdcinContext *s, AVFrame *frame)
179 int bit_pos, node_num, dat_pos;
181 prev = bit_pos = dat_pos = 0;
182 for (y = 0; y < (frame->linesize[0] * s->avctx->height);
183 y += 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 frame->data[0][x] = node_num;
211 static int idcin_decode_frame(AVCodecContext *avctx,
212 void *data, int *got_frame,
215 const uint8_t *buf = avpkt->data;
216 int buf_size = avpkt->size;
217 IdcinContext *s = avctx->priv_data;
218 const uint8_t *pal = av_packet_get_side_data(avpkt, AV_PKT_DATA_PALETTE, NULL);
219 AVFrame *frame = data;
225 if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
228 if (idcin_decode_vlcs(s, frame))
229 return AVERROR_INVALIDDATA;
232 frame->palette_has_changed = 1;
233 memcpy(s->pal, pal, AVPALETTE_SIZE);
235 /* make the palette available on the way out */
236 memcpy(frame->data[1], s->pal, AVPALETTE_SIZE);
240 /* report that the buffer was completely consumed */
244 AVCodec ff_idcin_decoder = {
245 .name = "idcinvideo",
246 .long_name = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),
247 .type = AVMEDIA_TYPE_VIDEO,
248 .id = AV_CODEC_ID_IDCIN,
249 .priv_data_size = sizeof(IdcinContext),
250 .init = idcin_decode_init,
251 .decode = idcin_decode_frame,
252 .capabilities = CODEC_CAP_DR1,