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 libavcodec/idcinvideo.c
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 ffmpeg'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#include <unistd.h>
51
52#include "avcodec.h"
53
54#define HUFFMAN_TABLE_SIZE 64 * 1024
55#define HUF_TOKENS 256
56#define PALETTE_COUNT 256
57
58typedef struct
59{
60  int count;
61  unsigned char used;
62  int children[2];
63} hnode;
64
65typedef struct IdcinContext {
66
67    AVCodecContext *avctx;
68    AVFrame frame;
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} 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 * Returns the node index of the lowest unused node, or -1 if all nodes
82 * are used.
83 */
84static 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 */
116static 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
146static 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 = 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    s->frame.data[0] = NULL;
170
171    return 0;
172}
173
174static void idcin_decode_vlcs(IdcinContext *s)
175{
176    hnode *hnodes;
177    long x, y;
178    int prev;
179    unsigned char v = 0;
180    int bit_pos, node_num, dat_pos;
181
182    prev = bit_pos = dat_pos = 0;
183    for (y = 0; y < (s->frame.linesize[0] * s->avctx->height);
184        y += s->frame.linesize[0]) {
185        for (x = y; x < y + s->avctx->width; x++) {
186            node_num = s->num_huff_nodes[prev];
187            hnodes = s->huff_nodes[prev];
188
189            while(node_num >= HUF_TOKENS) {
190                if(!bit_pos) {
191                    if(dat_pos >= s->size) {
192                        av_log(s->avctx, AV_LOG_ERROR, "Huffman decode error.\n");
193                        return;
194                    }
195                    bit_pos = 8;
196                    v = s->buf[dat_pos++];
197                }
198
199                node_num = hnodes[node_num].children[v & 0x01];
200                v = v >> 1;
201                bit_pos--;
202            }
203
204            s->frame.data[0][x] = node_num;
205            prev = node_num;
206        }
207    }
208}
209
210static int idcin_decode_frame(AVCodecContext *avctx,
211                              void *data, int *data_size,
212                              const uint8_t *buf, int buf_size)
213{
214    IdcinContext *s = avctx->priv_data;
215    AVPaletteControl *palette_control = avctx->palctrl;
216
217    s->buf = buf;
218    s->size = buf_size;
219
220    if (s->frame.data[0])
221        avctx->release_buffer(avctx, &s->frame);
222
223    if (avctx->get_buffer(avctx, &s->frame)) {
224        av_log(avctx, AV_LOG_ERROR, "  id CIN Video: get_buffer() failed\n");
225        return -1;
226    }
227
228    idcin_decode_vlcs(s);
229
230    /* make the palette available on the way out */
231    memcpy(s->frame.data[1], palette_control->palette, PALETTE_COUNT * 4);
232    /* If palette changed inform application*/
233    if (palette_control->palette_changed) {
234        palette_control->palette_changed = 0;
235        s->frame.palette_has_changed = 1;
236    }
237
238    *data_size = sizeof(AVFrame);
239    *(AVFrame*)data = s->frame;
240
241    /* report that the buffer was completely consumed */
242    return buf_size;
243}
244
245static av_cold int idcin_decode_end(AVCodecContext *avctx)
246{
247    IdcinContext *s = avctx->priv_data;
248
249    if (s->frame.data[0])
250        avctx->release_buffer(avctx, &s->frame);
251
252    return 0;
253}
254
255AVCodec idcin_decoder = {
256    "idcinvideo",
257    CODEC_TYPE_VIDEO,
258    CODEC_ID_IDCIN,
259    sizeof(IdcinContext),
260    idcin_decode_init,
261    NULL,
262    idcin_decode_end,
263    idcin_decode_frame,
264    CODEC_CAP_DR1,
265    .long_name = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),
266};
267
268