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 "codec_internal.h"
53#include "decode.h"
54#include "internal.h"
55#include "libavutil/internal.h"
56
57#define HUFFMAN_TABLE_SIZE 64 * 1024
58#define HUF_TOKENS 256
59#define PALETTE_COUNT 256
60
61typedef struct hnode {
62  int count;
63  unsigned char used;
64  int children[2];
65} hnode;
66
67typedef struct IdcinContext {
68
69    AVCodecContext *avctx;
70
71    const unsigned char *buf;
72    int size;
73
74    hnode huff_nodes[256][HUF_TOKENS*2];
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 */
86static 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 */
118static 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
148static av_cold int idcin_decode_init(AVCodecContext *avctx)
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 */
158    if (s->avctx->extradata_size != HUFFMAN_TABLE_SIZE) {
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
171    return 0;
172}
173
174static int idcin_decode_vlcs(IdcinContext *s, AVFrame *frame)
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 < (frame->linesize[0] * s->avctx->height);
184        y += 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 -1;
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            frame->data[0][x] = node_num;
205            prev = node_num;
206        }
207    }
208
209    return 0;
210}
211
212static int idcin_decode_frame(AVCodecContext *avctx, AVFrame *frame,
213                              int *got_frame, AVPacket *avpkt)
214{
215    const uint8_t *buf = avpkt->data;
216    int buf_size = avpkt->size;
217    IdcinContext *s = avctx->priv_data;
218    int ret;
219
220    s->buf = buf;
221    s->size = buf_size;
222
223    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
224        return ret;
225
226    if (idcin_decode_vlcs(s, frame))
227        return AVERROR_INVALIDDATA;
228
229    frame->palette_has_changed = ff_copy_palette(s->pal, avpkt, avctx);
230    /* make the palette available on the way out */
231    memcpy(frame->data[1], s->pal, AVPALETTE_SIZE);
232
233    *got_frame = 1;
234
235    /* report that the buffer was completely consumed */
236    return buf_size;
237}
238
239static const FFCodecDefault idcin_defaults[] = {
240    { "max_pixels", "320*240" },
241    { NULL },
242};
243
244const FFCodec ff_idcin_decoder = {
245    .p.name         = "idcinvideo",
246    .p.long_name    = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),
247    .p.type         = AVMEDIA_TYPE_VIDEO,
248    .p.id           = AV_CODEC_ID_IDCIN,
249    .priv_data_size = sizeof(IdcinContext),
250    .init           = idcin_decode_init,
251    FF_CODEC_DECODE_CB(idcin_decode_frame),
252    .p.capabilities = AV_CODEC_CAP_DR1,
253    .defaults       = idcin_defaults,
254    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
255};
256