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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 | |
60 | { | |
61 | int count; | |
62 | unsigned char used; | |
63 | int children[2]; | |
64 | } hnode; | |
65 | ||
66 | typedef struct IdcinContext { | |
67 | ||
68 | AVCodecContext *avctx; | |
69 | ||
70 | const unsigned char *buf; | |
71 | int size; | |
72 | ||
73 | hnode huff_nodes[256][HUF_TOKENS*2]; | |
74 | int num_huff_nodes[256]; | |
75 | ||
76 | uint32_t pal[256]; | |
77 | } IdcinContext; | |
78 | ||
79 | /** | |
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 | |
83 | * are used. | |
84 | */ | |
85 | static int huff_smallest_node(hnode *hnodes, int num_hnodes) { | |
86 | int i; | |
87 | int best, best_node; | |
88 | ||
89 | best = 99999999; | |
90 | best_node = -1; | |
91 | for(i = 0; i < num_hnodes; i++) { | |
92 | if(hnodes[i].used) | |
93 | continue; | |
94 | if(!hnodes[i].count) | |
95 | continue; | |
96 | if(hnodes[i].count < best) { | |
97 | best = hnodes[i].count; | |
98 | best_node = i; | |
99 | } | |
100 | } | |
101 | ||
102 | if(best_node == -1) | |
103 | return -1; | |
104 | hnodes[best_node].used = 1; | |
105 | return best_node; | |
106 | } | |
107 | ||
108 | /* | |
109 | * Build the Huffman tree using the generated/loaded probabilities histogram. | |
110 | * | |
111 | * On completion: | |
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. | |
116 | */ | |
117 | static av_cold void huff_build_tree(IdcinContext *s, int prev) { | |
118 | hnode *node, *hnodes; | |
119 | int num_hnodes, i; | |
120 | ||
121 | num_hnodes = HUF_TOKENS; | |
122 | hnodes = s->huff_nodes[prev]; | |
123 | for(i = 0; i < HUF_TOKENS * 2; i++) | |
124 | hnodes[i].used = 0; | |
125 | ||
126 | while (1) { | |
127 | node = &hnodes[num_hnodes]; /* next free node */ | |
128 | ||
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 */ | |
133 | ||
134 | node->children[1] = huff_smallest_node(hnodes, num_hnodes); | |
135 | if(node->children[1] == -1) | |
136 | break; /* reached the root node */ | |
137 | ||
138 | /* combine nodes probability for new node */ | |
139 | node->count = hnodes[node->children[0]].count + | |
140 | hnodes[node->children[1]].count; | |
141 | num_hnodes++; | |
142 | } | |
143 | ||
144 | s->num_huff_nodes[prev] = num_hnodes - 1; | |
145 | } | |
146 | ||
147 | static av_cold int idcin_decode_init(AVCodecContext *avctx) | |
148 | { | |
149 | IdcinContext *s = avctx->priv_data; | |
150 | int i, j, histogram_index = 0; | |
151 | unsigned char *histograms; | |
152 | ||
153 | s->avctx = avctx; | |
154 | avctx->pix_fmt = AV_PIX_FMT_PAL8; | |
155 | ||
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); | |
159 | return -1; | |
160 | } | |
161 | ||
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); | |
168 | } | |
169 | ||
170 | return 0; | |
171 | } | |
172 | ||
173 | static int idcin_decode_vlcs(IdcinContext *s, AVFrame *frame) | |
174 | { | |
175 | hnode *hnodes; | |
176 | long x, y; | |
177 | int prev; | |
178 | unsigned char v = 0; | |
179 | int bit_pos, node_num, dat_pos; | |
180 | ||
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]; | |
187 | ||
188 | while(node_num >= HUF_TOKENS) { | |
189 | if(!bit_pos) { | |
190 | if(dat_pos >= s->size) { | |
191 | av_log(s->avctx, AV_LOG_ERROR, "Huffman decode error.\n"); | |
192 | return -1; | |
193 | } | |
194 | bit_pos = 8; | |
195 | v = s->buf[dat_pos++]; | |
196 | } | |
197 | ||
198 | node_num = hnodes[node_num].children[v & 0x01]; | |
199 | v = v >> 1; | |
200 | bit_pos--; | |
201 | } | |
202 | ||
203 | frame->data[0][x] = node_num; | |
204 | prev = node_num; | |
205 | } | |
206 | } | |
207 | ||
208 | return 0; | |
209 | } | |
210 | ||
211 | static int idcin_decode_frame(AVCodecContext *avctx, | |
212 | void *data, int *got_frame, | |
213 | AVPacket *avpkt) | |
214 | { | |
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; | |
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) { | |
232 | frame->palette_has_changed = 1; | |
233 | memcpy(s->pal, pal, AVPALETTE_SIZE); | |
234 | } | |
235 | /* make the palette available on the way out */ | |
236 | memcpy(frame->data[1], s->pal, AVPALETTE_SIZE); | |
237 | ||
238 | *got_frame = 1; | |
239 | ||
240 | /* report that the buffer was completely consumed */ | |
241 | return buf_size; | |
242 | } | |
243 | ||
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, | |
253 | }; |