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idcinvideo.c
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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 
70 
71  const unsigned char *buf;
72  int size;
73 
75  int num_huff_nodes[256];
76 
77  uint32_t pal[256];
78 } IdcinContext;
79 
80 /**
81  * Find the lowest probability node in a Huffman table, and mark it as
82  * being assigned to a higher probability.
83  * @return the node index of the lowest unused node, or -1 if all nodes
84  * are used.
85  */
86 static int huff_smallest_node(hnode *hnodes, int num_hnodes) {
87  int i;
88  int best, best_node;
89 
90  best = 99999999;
91  best_node = -1;
92  for(i = 0; i < num_hnodes; i++) {
93  if(hnodes[i].used)
94  continue;
95  if(!hnodes[i].count)
96  continue;
97  if(hnodes[i].count < best) {
98  best = hnodes[i].count;
99  best_node = i;
100  }
101  }
102 
103  if(best_node == -1)
104  return -1;
105  hnodes[best_node].used = 1;
106  return best_node;
107 }
108 
109 /*
110  * Build the Huffman tree using the generated/loaded probabilities histogram.
111  *
112  * On completion:
113  * huff_nodes[prev][i < HUF_TOKENS] - are the nodes at the base of the tree.
114  * huff_nodes[prev][i >= HUF_TOKENS] - are used to construct the tree.
115  * num_huff_nodes[prev] - contains the index to the root node of the tree.
116  * That is: huff_nodes[prev][num_huff_nodes[prev]] is the root node.
117  */
118 static av_cold void huff_build_tree(IdcinContext *s, int prev) {
119  hnode *node, *hnodes;
120  int num_hnodes, i;
121 
122  num_hnodes = HUF_TOKENS;
123  hnodes = s->huff_nodes[prev];
124  for(i = 0; i < HUF_TOKENS * 2; i++)
125  hnodes[i].used = 0;
126 
127  while (1) {
128  node = &hnodes[num_hnodes]; /* next free node */
129 
130  /* pick two lowest counts */
131  node->children[0] = huff_smallest_node(hnodes, num_hnodes);
132  if(node->children[0] == -1)
133  break; /* reached the root node */
134 
135  node->children[1] = huff_smallest_node(hnodes, num_hnodes);
136  if(node->children[1] == -1)
137  break; /* reached the root node */
138 
139  /* combine nodes probability for new node */
140  node->count = hnodes[node->children[0]].count +
141  hnodes[node->children[1]].count;
142  num_hnodes++;
143  }
144 
145  s->num_huff_nodes[prev] = num_hnodes - 1;
146 }
147 
149 {
150  IdcinContext *s = avctx->priv_data;
151  int i, j, histogram_index = 0;
152  unsigned char *histograms;
153 
154  s->avctx = avctx;
155  avctx->pix_fmt = AV_PIX_FMT_PAL8;
156 
157  /* make sure the Huffman tables make it */
159  av_log(s->avctx, AV_LOG_ERROR, " id CIN video: expected extradata size of %d\n", HUFFMAN_TABLE_SIZE);
160  return -1;
161  }
162 
163  /* build the 256 Huffman decode trees */
164  histograms = (unsigned char *)s->avctx->extradata;
165  for (i = 0; i < 256; i++) {
166  for(j = 0; j < HUF_TOKENS; j++)
167  s->huff_nodes[i][j].count = histograms[histogram_index++];
168  huff_build_tree(s, i);
169  }
170 
172  s->frame.data[0] = NULL;
173 
174  return 0;
175 }
176 
178 {
179  hnode *hnodes;
180  long x, y;
181  int prev;
182  unsigned char v = 0;
183  int bit_pos, node_num, dat_pos;
184 
185  prev = bit_pos = dat_pos = 0;
186  for (y = 0; y < (s->frame.linesize[0] * s->avctx->height);
187  y += s->frame.linesize[0]) {
188  for (x = y; x < y + s->avctx->width; x++) {
189  node_num = s->num_huff_nodes[prev];
190  hnodes = s->huff_nodes[prev];
191 
192  while(node_num >= HUF_TOKENS) {
193  if(!bit_pos) {
194  if(dat_pos >= s->size) {
195  av_log(s->avctx, AV_LOG_ERROR, "Huffman decode error.\n");
196  return -1;
197  }
198  bit_pos = 8;
199  v = s->buf[dat_pos++];
200  }
201 
202  node_num = hnodes[node_num].children[v & 0x01];
203  v = v >> 1;
204  bit_pos--;
205  }
206 
207  s->frame.data[0][x] = node_num;
208  prev = node_num;
209  }
210  }
211 
212  return 0;
213 }
214 
216  void *data, int *got_frame,
217  AVPacket *avpkt)
218 {
219  const uint8_t *buf = avpkt->data;
220  int buf_size = avpkt->size;
221  IdcinContext *s = avctx->priv_data;
223  int ret;
224 
225  s->buf = buf;
226  s->size = buf_size;
227 
228  if (s->frame.data[0])
229  avctx->release_buffer(avctx, &s->frame);
230 
231  if ((ret = ff_get_buffer(avctx, &s->frame))) {
232  av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
233  return ret;
234  }
235 
236  if (idcin_decode_vlcs(s))
237  return AVERROR_INVALIDDATA;
238 
239  if (pal) {
240  s->frame.palette_has_changed = 1;
241  memcpy(s->pal, pal, AVPALETTE_SIZE);
242  }
243  /* make the palette available on the way out */
244  memcpy(s->frame.data[1], s->pal, AVPALETTE_SIZE);
245 
246  *got_frame = 1;
247  *(AVFrame*)data = s->frame;
248 
249  /* report that the buffer was completely consumed */
250  return buf_size;
251 }
252 
254 {
255  IdcinContext *s = avctx->priv_data;
256 
257  if (s->frame.data[0])
258  avctx->release_buffer(avctx, &s->frame);
259 
260  return 0;
261 }
262 
264  .name = "idcinvideo",
265  .type = AVMEDIA_TYPE_VIDEO,
266  .id = AV_CODEC_ID_IDCIN,
267  .priv_data_size = sizeof(IdcinContext),
271  .capabilities = CODEC_CAP_DR1,
272  .long_name = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),
273 };