Statistics
| Branch: | Revision:

ffmpeg / libavcodec / idcinvideo.c @ 08f7073a

History | View | Annotate | Download (7.72 KB)

1
/*
2
 * Id Quake II CIN Video Decoder
3
 * Copyright (C) 2003 the ffmpeg project
4
 *
5
 * This library is free software; you can redistribute it and/or
6
 * modify it under the terms of the GNU Lesser General Public
7
 * License as published by the Free Software Foundation; either
8
 * version 2 of the License, or (at your option) any later version.
9
 *
10
 * This library is distributed in the hope that it will be useful,
11
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13
 * Lesser General Public License for more details.
14
 *
15
 * You should have received a copy of the GNU Lesser General Public
16
 * License along with this library; if not, write to the Free Software
17
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
18
 *
19
 */
20

    
21
/**
22
 * @file idcinvideo.c
23
 * Id Quake II Cin Video Decoder by Dr. Tim Ferguson
24
 * For more information about the Id CIN format, visit:
25
 *   http://www.csse.monash.edu.au/~timf/
26
 *
27
 * This video decoder outputs PAL8 colorspace data. Interacting with this
28
 * decoder is a little involved. During initialization, the demuxer must
29
 * transmit the 65536-byte Huffman table(s) to the decoder via extradata.
30
 * Then, whenever a palette change is encountered while demuxing the file,
31
 * the demuxer must use the same extradata space to transmit an
32
 * AVPaletteControl structure.
33
 *
34
 * Id CIN video is purely Huffman-coded, intraframe-only codec. It achieves
35
 * a little more compression by exploiting the fact that adjacent pixels
36
 * tend to be similar.
37
 *
38
 * Note that this decoder could use ffmpeg's optimized VLC facilities
39
 * rather than naive, tree-based Huffman decoding. However, there are 256
40
 * Huffman tables. Plus, the VLC bit coding order is right -> left instead
41
 * or left -> right, so all of the bits would have to be reversed. Further,
42
 * the original Quake II implementation likely used a similar naive
43
 * decoding algorithm and it worked fine on much lower spec machines.
44
 */
45

    
46
#include <stdio.h>
47
#include <stdlib.h>
48
#include <string.h>
49
#include <unistd.h>
50

    
51
#include "common.h"
52
#include "avcodec.h"
53
#include "dsputil.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_t;
65

    
66
typedef struct IdcinContext {
67

    
68
    AVCodecContext *avctx;
69
    DSPContext dsp;
70
    AVFrame frame;
71

    
72
    unsigned char *buf;
73
    int size;
74

    
75
    hnode_t huff_nodes[256][HUF_TOKENS*2];
76
    int num_huff_nodes[256];
77

    
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
 * Returns the node index of the lowest unused node, or -1 if all nodes
84
 * are used.
85
 */
86
static int huff_smallest_node(hnode_t *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 void huff_build_tree(IdcinContext *s, int prev) {
119
    hnode_t *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

    
148
static int idcin_decode_init(AVCodecContext *avctx)
149
{
150
    IdcinContext *s = (IdcinContext *)avctx->priv_data;
151
    int i, j, histogram_index = 0;
152
    unsigned char *histograms;
153

    
154
    s->avctx = avctx;
155
    avctx->pix_fmt = PIX_FMT_PAL8;
156
    avctx->has_b_frames = 0;
157
    dsputil_init(&s->dsp, avctx);
158

    
159
    /* make sure the Huffman tables make it */
160
    if (s->avctx->extradata_size != HUFFMAN_TABLE_SIZE) {
161
        av_log(s->avctx, AV_LOG_ERROR, "  Id CIN video: expected extradata size of %d\n", HUFFMAN_TABLE_SIZE);
162
        return -1;
163
    }
164

    
165
    /* build the 256 Huffman decode trees */
166
    histograms = (unsigned char *)s->avctx->extradata;
167
    for (i = 0; i < 256; i++) {
168
        for(j = 0; j < HUF_TOKENS; j++)
169
            s->huff_nodes[i][j].count = histograms[histogram_index++];
170
        huff_build_tree(s, i);
171
    }
172

    
173
    s->frame.data[0] = NULL;
174

    
175
    return 0;
176
}
177

    
178
static void idcin_decode_vlcs(IdcinContext *s)
179
{
180
    hnode_t *hnodes;
181
    long x, y;
182
    int prev;
183
    unsigned char v = 0;
184
    int bit_pos, node_num, dat_pos;
185

    
186
    prev = bit_pos = dat_pos = 0;
187
    for (y = 0; y < (s->frame.linesize[0] * s->avctx->height);
188
        y += s->frame.linesize[0]) {
189
        for (x = y; x < y + s->avctx->width; x++) {
190
            node_num = s->num_huff_nodes[prev];
191
            hnodes = s->huff_nodes[prev];
192

    
193
            while(node_num >= HUF_TOKENS) {
194
                if(!bit_pos) {
195
                    if(dat_pos > s->size) {
196
                        av_log(s->avctx, AV_LOG_ERROR, "Huffman decode error.\n");
197
                        return;
198
                    }
199
                    bit_pos = 8;
200
                    v = s->buf[dat_pos++];
201
                }
202

    
203
                node_num = hnodes[node_num].children[v & 0x01];
204
                v = v >> 1;
205
                bit_pos--;
206
            }
207

    
208
            s->frame.data[0][x] = node_num;
209
            prev = node_num;
210
        }
211
    }
212
}
213

    
214
static int idcin_decode_frame(AVCodecContext *avctx,
215
                              void *data, int *data_size,
216
                              uint8_t *buf, int buf_size)
217
{
218
    IdcinContext *s = (IdcinContext *)avctx->priv_data;
219
    AVPaletteControl *palette_control = avctx->palctrl;
220

    
221
    s->buf = buf;
222
    s->size = buf_size;
223

    
224
    if (s->frame.data[0])
225
        avctx->release_buffer(avctx, &s->frame);
226

    
227
    if (avctx->get_buffer(avctx, &s->frame)) {
228
        av_log(avctx, AV_LOG_ERROR, "  Id CIN Video: get_buffer() failed\n");
229
        return -1;
230
    }
231

    
232
    idcin_decode_vlcs(s);
233

    
234
    /* make the palette available on the way out */
235
    memcpy(s->frame.data[1], palette_control->palette, PALETTE_COUNT * 4);
236
    /* If palette changed inform application*/
237
    if (palette_control->palette_changed) {
238
        palette_control->palette_changed = 0;
239
        s->frame.palette_has_changed = 1;
240
    }
241

    
242
    *data_size = sizeof(AVFrame);
243
    *(AVFrame*)data = s->frame;
244

    
245
    /* report that the buffer was completely consumed */
246
    return buf_size;
247
}
248

    
249
static int idcin_decode_end(AVCodecContext *avctx)
250
{
251
    IdcinContext *s = (IdcinContext *)avctx->priv_data;
252

    
253
    if (s->frame.data[0])
254
        avctx->release_buffer(avctx, &s->frame);
255

    
256
    return 0;
257
}
258

    
259
AVCodec idcin_decoder = {
260
    "idcinvideo",
261
    CODEC_TYPE_VIDEO,
262
    CODEC_ID_IDCIN,
263
    sizeof(IdcinContext),
264
    idcin_decode_init,
265
    NULL,
266
    idcin_decode_end,
267
    idcin_decode_frame,
268
    CODEC_CAP_DR1,
269
};
270