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 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.
45 */
46
47 #include <stdio.h>
48 #include <stdlib.h>
49 #include <string.h>
50
51 #include "avcodec.h"
52 #include "internal.h"
53 #include "libavutil/internal.h"
54
55 #define HUFFMAN_TABLE_SIZE 64 * 1024
56 #define HUF_TOKENS 256
57 #define PALETTE_COUNT 256
58
59 typedef struct hnode {
60 int count;
61 unsigned char used;
62 int children[2];
63 } hnode;
64
65 typedef struct IdcinContext {
66
67 AVCodecContext *avctx;
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 uint32_t pal[256];
76 } IdcinContext;
77
78 /**
79 * Find the lowest probability node in a Huffman table, and mark it as
80 * being assigned to a higher probability.
81 * @return the node index of the lowest unused node, or -1 if all nodes
82 * are used.
83 */
huff_smallest_node(hnode * hnodes,int num_hnodes)84 static int huff_smallest_node(hnode *hnodes, int num_hnodes) {
85 int i;
86 int best, best_node;
87
88 best = 99999999;
89 best_node = -1;
90 for(i = 0; i < num_hnodes; i++) {
91 if(hnodes[i].used)
92 continue;
93 if(!hnodes[i].count)
94 continue;
95 if(hnodes[i].count < best) {
96 best = hnodes[i].count;
97 best_node = i;
98 }
99 }
100
101 if(best_node == -1)
102 return -1;
103 hnodes[best_node].used = 1;
104 return best_node;
105 }
106
107 /*
108 * Build the Huffman tree using the generated/loaded probabilities histogram.
109 *
110 * On completion:
111 * huff_nodes[prev][i < HUF_TOKENS] - are the nodes at the base of the tree.
112 * huff_nodes[prev][i >= HUF_TOKENS] - are used to construct the tree.
113 * num_huff_nodes[prev] - contains the index to the root node of the tree.
114 * That is: huff_nodes[prev][num_huff_nodes[prev]] is the root node.
115 */
huff_build_tree(IdcinContext * s,int prev)116 static av_cold void huff_build_tree(IdcinContext *s, int prev) {
117 hnode *node, *hnodes;
118 int num_hnodes, i;
119
120 num_hnodes = HUF_TOKENS;
121 hnodes = s->huff_nodes[prev];
122 for(i = 0; i < HUF_TOKENS * 2; i++)
123 hnodes[i].used = 0;
124
125 while (1) {
126 node = &hnodes[num_hnodes]; /* next free node */
127
128 /* pick two lowest counts */
129 node->children[0] = huff_smallest_node(hnodes, num_hnodes);
130 if(node->children[0] == -1)
131 break; /* reached the root node */
132
133 node->children[1] = huff_smallest_node(hnodes, num_hnodes);
134 if(node->children[1] == -1)
135 break; /* reached the root node */
136
137 /* combine nodes probability for new node */
138 node->count = hnodes[node->children[0]].count +
139 hnodes[node->children[1]].count;
140 num_hnodes++;
141 }
142
143 s->num_huff_nodes[prev] = num_hnodes - 1;
144 }
145
idcin_decode_init(AVCodecContext * avctx)146 static av_cold int idcin_decode_init(AVCodecContext *avctx)
147 {
148 IdcinContext *s = avctx->priv_data;
149 int i, j, histogram_index = 0;
150 unsigned char *histograms;
151
152 s->avctx = avctx;
153 avctx->pix_fmt = AV_PIX_FMT_PAL8;
154
155 /* make sure the Huffman tables make it */
156 if (s->avctx->extradata_size != HUFFMAN_TABLE_SIZE) {
157 av_log(s->avctx, AV_LOG_ERROR, " id CIN video: expected extradata size of %d\n", HUFFMAN_TABLE_SIZE);
158 return -1;
159 }
160
161 /* build the 256 Huffman decode trees */
162 histograms = (unsigned char *)s->avctx->extradata;
163 for (i = 0; i < 256; i++) {
164 for(j = 0; j < HUF_TOKENS; j++)
165 s->huff_nodes[i][j].count = histograms[histogram_index++];
166 huff_build_tree(s, i);
167 }
168
169 return 0;
170 }
171
idcin_decode_vlcs(IdcinContext * s,AVFrame * frame)172 static int idcin_decode_vlcs(IdcinContext *s, AVFrame *frame)
173 {
174 hnode *hnodes;
175 long x, y;
176 int prev;
177 unsigned char v = 0;
178 int bit_pos, node_num, dat_pos;
179
180 prev = bit_pos = dat_pos = 0;
181 for (y = 0; y < (frame->linesize[0] * s->avctx->height);
182 y += frame->linesize[0]) {
183 for (x = y; x < y + s->avctx->width; x++) {
184 node_num = s->num_huff_nodes[prev];
185 hnodes = s->huff_nodes[prev];
186
187 while(node_num >= HUF_TOKENS) {
188 if(!bit_pos) {
189 if(dat_pos >= s->size) {
190 av_log(s->avctx, AV_LOG_ERROR, "Huffman decode error.\n");
191 return -1;
192 }
193 bit_pos = 8;
194 v = s->buf[dat_pos++];
195 }
196
197 node_num = hnodes[node_num].children[v & 0x01];
198 v = v >> 1;
199 bit_pos--;
200 }
201
202 frame->data[0][x] = node_num;
203 prev = node_num;
204 }
205 }
206
207 return 0;
208 }
209
idcin_decode_frame(AVCodecContext * avctx,void * data,int * got_frame,AVPacket * avpkt)210 static int idcin_decode_frame(AVCodecContext *avctx,
211 void *data, int *got_frame,
212 AVPacket *avpkt)
213 {
214 const uint8_t *buf = avpkt->data;
215 int buf_size = avpkt->size;
216 IdcinContext *s = avctx->priv_data;
217 buffer_size_t pal_size;
218 const uint8_t *pal = av_packet_get_side_data(avpkt, AV_PKT_DATA_PALETTE, &pal_size);
219 AVFrame *frame = data;
220 int ret;
221
222 s->buf = buf;
223 s->size = buf_size;
224
225 if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
226 return ret;
227
228 if (idcin_decode_vlcs(s, frame))
229 return AVERROR_INVALIDDATA;
230
231 if (pal && pal_size == AVPALETTE_SIZE) {
232 frame->palette_has_changed = 1;
233 memcpy(s->pal, pal, AVPALETTE_SIZE);
234 } else if (pal) {
235 av_log(avctx, AV_LOG_ERROR, "Palette size %d is wrong\n", pal_size);
236 }
237 /* make the palette available on the way out */
238 memcpy(frame->data[1], s->pal, AVPALETTE_SIZE);
239
240 *got_frame = 1;
241
242 /* report that the buffer was completely consumed */
243 return buf_size;
244 }
245
246 static const AVCodecDefault idcin_defaults[] = {
247 { "max_pixels", "320*240" },
248 { NULL },
249 };
250
251 AVCodec ff_idcin_decoder = {
252 .name = "idcinvideo",
253 .long_name = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),
254 .type = AVMEDIA_TYPE_VIDEO,
255 .id = AV_CODEC_ID_IDCIN,
256 .priv_data_size = sizeof(IdcinContext),
257 .init = idcin_decode_init,
258 .decode = idcin_decode_frame,
259 .capabilities = AV_CODEC_CAP_DR1,
260 .defaults = idcin_defaults,
261 .caps_internal = FF_CODEC_CAP_INIT_THREADSAFE,
262 };
263