2 * id Quake II CIN Video Decoder
3 * Copyright (C) 2003 the ffmpeg project
5 * This file is part of Libav.
7 * Libav 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.
12 * Libav 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.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with Libav; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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/
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.
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
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.
53 #include "libavutil/internal.h"
55 #define HUFFMAN_TABLE_SIZE 64 * 1024
56 #define HUF_TOKENS 256
57 #define PALETTE_COUNT 256
66 typedef struct IdcinContext
{
68 AVCodecContext
*avctx
;
71 const unsigned char *buf
;
74 hnode huff_nodes
[256][HUF_TOKENS
*2];
75 int num_huff_nodes
[256];
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
86 static int huff_smallest_node(hnode
*hnodes
, int num_hnodes
) {
92 for(i
= 0; i
< num_hnodes
; i
++) {
97 if(hnodes
[i
].count
< best
) {
98 best
= hnodes
[i
].count
;
105 hnodes
[best_node
].used
= 1;
110 * Build the Huffman tree using the generated/loaded probabilities histogram.
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.
118 static av_cold
void huff_build_tree(IdcinContext
*s
, int prev
) {
119 hnode
*node
, *hnodes
;
122 num_hnodes
= HUF_TOKENS
;
123 hnodes
= s
->huff_nodes
[prev
];
124 for(i
= 0; i
< HUF_TOKENS
* 2; i
++)
128 node
= &hnodes
[num_hnodes
]; /* next free node */
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 */
135 node
->children
[1] = huff_smallest_node(hnodes
, num_hnodes
);
136 if(node
->children
[1] == -1)
137 break; /* reached the root node */
139 /* combine nodes probability for new node */
140 node
->count
= hnodes
[node
->children
[0]].count
+
141 hnodes
[node
->children
[1]].count
;
145 s
->num_huff_nodes
[prev
] = num_hnodes
- 1;
148 static av_cold
int idcin_decode_init(AVCodecContext
*avctx
)
150 IdcinContext
*s
= avctx
->priv_data
;
151 int i
, j
, histogram_index
= 0;
152 unsigned char *histograms
;
155 avctx
->pix_fmt
= AV_PIX_FMT_PAL8
;
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
);
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
);
171 avcodec_get_frame_defaults(&s
->frame
);
176 static void idcin_decode_vlcs(IdcinContext
*s
)
182 int bit_pos
, node_num
, dat_pos
;
184 prev
= bit_pos
= dat_pos
= 0;
185 for (y
= 0; y
< (s
->frame
.linesize
[0] * s
->avctx
->height
);
186 y
+= s
->frame
.linesize
[0]) {
187 for (x
= y
; x
< y
+ s
->avctx
->width
; x
++) {
188 node_num
= s
->num_huff_nodes
[prev
];
189 hnodes
= s
->huff_nodes
[prev
];
191 while(node_num
>= HUF_TOKENS
) {
193 if(dat_pos
>= s
->size
) {
194 av_log(s
->avctx
, AV_LOG_ERROR
, "Huffman decode error.\n");
198 v
= s
->buf
[dat_pos
++];
201 node_num
= hnodes
[node_num
].children
[v
& 0x01];
206 s
->frame
.data
[0][x
] = node_num
;
212 static int idcin_decode_frame(AVCodecContext
*avctx
,
213 void *data
, int *got_frame
,
216 const uint8_t *buf
= avpkt
->data
;
217 int buf_size
= avpkt
->size
;
218 IdcinContext
*s
= avctx
->priv_data
;
219 const uint8_t *pal
= av_packet_get_side_data(avpkt
, AV_PKT_DATA_PALETTE
, NULL
);
224 if (s
->frame
.data
[0])
225 avctx
->release_buffer(avctx
, &s
->frame
);
227 if (ff_get_buffer(avctx
, &s
->frame
)) {
228 av_log(avctx
, AV_LOG_ERROR
, " id CIN Video: get_buffer() failed\n");
232 idcin_decode_vlcs(s
);
235 s
->frame
.palette_has_changed
= 1;
236 memcpy(s
->pal
, pal
, AVPALETTE_SIZE
);
238 /* make the palette available on the way out */
239 memcpy(s
->frame
.data
[1], s
->pal
, AVPALETTE_SIZE
);
242 *(AVFrame
*)data
= s
->frame
;
244 /* report that the buffer was completely consumed */
248 static av_cold
int idcin_decode_end(AVCodecContext
*avctx
)
250 IdcinContext
*s
= avctx
->priv_data
;
252 if (s
->frame
.data
[0])
253 avctx
->release_buffer(avctx
, &s
->frame
);
258 AVCodec ff_idcin_decoder
= {
259 .name
= "idcinvideo",
260 .type
= AVMEDIA_TYPE_VIDEO
,
261 .id
= AV_CODEC_ID_IDCIN
,
262 .priv_data_size
= sizeof(IdcinContext
),
263 .init
= idcin_decode_init
,
264 .close
= idcin_decode_end
,
265 .decode
= idcin_decode_frame
,
266 .capabilities
= CODEC_CAP_DR1
,
267 .long_name
= NULL_IF_CONFIG_SMALL("id Quake II CIN video"),