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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 
69 
70  const unsigned char *buf;
71  int size;
72 
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 
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 */
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 
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 
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 
245  .name = "idcinvideo",
246  .type = AVMEDIA_TYPE_VIDEO,
247  .id = AV_CODEC_ID_IDCIN,
248  .priv_data_size = sizeof(IdcinContext),
251  .capabilities = CODEC_CAP_DR1,
252  .long_name = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),
253 };