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 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
51#include "avcodec.h"
52
53#define HUFFMAN_TABLE_SIZE 64 * 1024
54#define HUF_TOKENS 256
55#define PALETTE_COUNT 256
56
57typedef struct
58{
59  int count;
60  unsigned char used;
61  int children[2];
62} hnode;
63
64typedef struct IdcinContext {
65
66    AVCodecContext *avctx;
67    AVFrame frame;
68
69    const unsigned char *buf;
70    int size;
71
72    hnode huff_nodes[256][HUF_TOKENS*2];
73    int num_huff_nodes[256];
74
75} IdcinContext;
76
77/*
78 * Find the lowest probability node in a Huffman table, and mark it as
79 * being assigned to a higher probability.
80 * Returns the node index of the lowest unused node, or -1 if all nodes
81 * are used.
82 */
83static int huff_smallest_node(hnode *hnodes, int num_hnodes) {
84    int i;
85    int best, best_node;
86
87    best = 99999999;
88    best_node = -1;
89    for(i = 0; i < num_hnodes; i++) {
90        if(hnodes[i].used)
91            continue;
92        if(!hnodes[i].count)
93            continue;
94        if(hnodes[i].count < best) {
95            best = hnodes[i].count;
96            best_node = i;
97        }
98    }
99
100    if(best_node == -1)
101        return -1;
102    hnodes[best_node].used = 1;
103    return best_node;
104}
105
106/*
107 * Build the Huffman tree using the generated/loaded probabilities histogram.
108 *
109 * On completion:
110 *  huff_nodes[prev][i < HUF_TOKENS] - are the nodes at the base of the tree.
111 *  huff_nodes[prev][i >= HUF_TOKENS] - are used to construct the tree.
112 *  num_huff_nodes[prev] - contains the index to the root node of the tree.
113 *    That is: huff_nodes[prev][num_huff_nodes[prev]] is the root node.
114 */
115static av_cold void huff_build_tree(IdcinContext *s, int prev) {
116    hnode *node, *hnodes;
117     int num_hnodes, i;
118
119    num_hnodes = HUF_TOKENS;
120    hnodes = s->huff_nodes[prev];
121    for(i = 0; i < HUF_TOKENS * 2; i++)
122        hnodes[i].used = 0;
123
124    while (1) {
125        node = &hnodes[num_hnodes];             /* next free node */
126
127        /* pick two lowest counts */
128        node->children[0] = huff_smallest_node(hnodes, num_hnodes);
129        if(node->children[0] == -1)
130            break;      /* reached the root node */
131
132        node->children[1] = huff_smallest_node(hnodes, num_hnodes);
133        if(node->children[1] == -1)
134            break;      /* reached the root node */
135
136        /* combine nodes probability for new node */
137        node->count = hnodes[node->children[0]].count +
138        hnodes[node->children[1]].count;
139        num_hnodes++;
140    }
141
142    s->num_huff_nodes[prev] = num_hnodes - 1;
143}
144
145static av_cold int idcin_decode_init(AVCodecContext *avctx)
146{
147    IdcinContext *s = avctx->priv_data;
148    int i, j, histogram_index = 0;
149    unsigned char *histograms;
150
151    s->avctx = avctx;
152    avctx->pix_fmt = PIX_FMT_PAL8;
153
154    /* make sure the Huffman tables make it */
155    if (s->avctx->extradata_size != HUFFMAN_TABLE_SIZE) {
156        av_log(s->avctx, AV_LOG_ERROR, "  id CIN video: expected extradata size of %d\n", HUFFMAN_TABLE_SIZE);
157        return -1;
158    }
159
160    /* build the 256 Huffman decode trees */
161    histograms = (unsigned char *)s->avctx->extradata;
162    for (i = 0; i < 256; i++) {
163        for(j = 0; j < HUF_TOKENS; j++)
164            s->huff_nodes[i][j].count = histograms[histogram_index++];
165        huff_build_tree(s, i);
166    }
167
168    s->frame.data[0] = NULL;
169
170    return 0;
171}
172
173static void idcin_decode_vlcs(IdcinContext *s)
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 < (s->frame.linesize[0] * s->avctx->height);
183        y += s->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;
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            s->frame.data[0][x] = node_num;
204            prev = node_num;
205        }
206    }
207}
208
209static int idcin_decode_frame(AVCodecContext *avctx,
210                              void *data, int *data_size,
211                              AVPacket *avpkt)
212{
213    const uint8_t *buf = avpkt->data;
214    int buf_size = avpkt->size;
215    IdcinContext *s = avctx->priv_data;
216    AVPaletteControl *palette_control = avctx->palctrl;
217
218    s->buf = buf;
219    s->size = buf_size;
220
221    if (s->frame.data[0])
222        avctx->release_buffer(avctx, &s->frame);
223
224    if (avctx->get_buffer(avctx, &s->frame)) {
225        av_log(avctx, AV_LOG_ERROR, "  id CIN Video: get_buffer() failed\n");
226        return -1;
227    }
228
229    idcin_decode_vlcs(s);
230
231    /* make the palette available on the way out */
232    memcpy(s->frame.data[1], palette_control->palette, PALETTE_COUNT * 4);
233    /* If palette changed inform application*/
234    if (palette_control->palette_changed) {
235        palette_control->palette_changed = 0;
236        s->frame.palette_has_changed = 1;
237    }
238
239    *data_size = sizeof(AVFrame);
240    *(AVFrame*)data = s->frame;
241
242    /* report that the buffer was completely consumed */
243    return buf_size;
244}
245
246static av_cold int idcin_decode_end(AVCodecContext *avctx)
247{
248    IdcinContext *s = avctx->priv_data;
249
250    if (s->frame.data[0])
251        avctx->release_buffer(avctx, &s->frame);
252
253    return 0;
254}
255
256AVCodec idcin_decoder = {
257    "idcinvideo",
258    AVMEDIA_TYPE_VIDEO,
259    CODEC_ID_IDCIN,
260    sizeof(IdcinContext),
261    idcin_decode_init,
262    NULL,
263    idcin_decode_end,
264    idcin_decode_frame,
265    CODEC_CAP_DR1,
266    .long_name = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),
267};
268
269