FFmpeg: libavcodec/idcinvideo.c Source File

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libavcodec

idcinvideo.c

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1 /*

2 * id Quake II CIN Video Decoder

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 */

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 */

47 #include <stdio.h>

48 #include <stdlib.h>

49 #include <string.h>

51 #include "avcodec.h"

52 #include "internal.h"

53 #include "libavutil/internal.h"

55 #define HUFFMAN_TABLE_SIZE 64 * 1024

56 #define HUF_TOKENS 256

57 #define PALETTE_COUNT 256

59 typedef struct hnode {

60 int count;

61 unsigned char used;

62 int children[2];

63 } hnode;

65 typedef struct IdcinContext {

67 AVCodecContext *avctx;

69 const unsigned char *buf;

70 int size;

72 hnode huff_nodes[256][HUF_TOKENS*2];

73 int num_huff_nodes[256];

75 uint32_t pal[256];

76 } IdcinContext;

78 /**

79 * Find the lowest probability node in a Huffman table, and mark it as

80 * being assigned to a higher probability.

81 * @return the node index of the lowest unused node, or -1 if all nodes

82 * are used.

83 */

84 static int huff_smallest_node(hnode *hnodes, int num_hnodes) {

85 int i;

86 int best, best_node;

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 */

116 static 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

146 static 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 = AV_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 return 0;

170 }

171

172 static int idcin_decode_vlcs(IdcinContext *s, AVFrame *frame)

173 {

174 hnode *hnodes;

175 long x, y;

176 int prev;

177 unsigned char v = 0;

178 int bit_pos, node_num, dat_pos;

179

180 prev = bit_pos = dat_pos = 0;

181 for (y = 0; y < (frame->linesize[0] * s->avctx->height);

182 y += frame->linesize[0]) {

183 for (x = y; x < y + s->avctx->width; x++) {

184 node_num = s->num_huff_nodes[prev];

185 hnodes = s->huff_nodes[prev];

186

187 while(node_num >= HUF_TOKENS) {

188 if(!bit_pos) {

189 if(dat_pos >= s->size) {

190 av_log(s->avctx, AV_LOG_ERROR, "Huffman decode error.\n");

191 return -1;

192 }

193 bit_pos = 8;

194 v = s->buf[dat_pos++];

195 }

196

197 node_num = hnodes[node_num].children[v & 0x01];

198 v = v >> 1;

199 bit_pos--;

200 }

201

202 frame->data[0][x] = node_num;

203 prev = node_num;

204 }

205 }

206

207 return 0;

208 }

209

210 static int idcin_decode_frame(AVCodecContext *avctx,

211 void *data, int *got_frame,

212 AVPacket *avpkt)

213 {

214 const uint8_t *buf = avpkt->data;

215 int buf_size = avpkt->size;

216 IdcinContext *s = avctx->priv_data;

217 const uint8_t *pal = av_packet_get_side_data(avpkt, AV_PKT_DATA_PALETTE, NULL);

218 AVFrame *frame = data;

219 int ret;

220

221 s->buf = buf;

222 s->size = buf_size;

223

224 if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)

225 return ret;

226

227 if (idcin_decode_vlcs(s, frame))

228 return AVERROR_INVALIDDATA;

229

230 if (pal) {

231 frame->palette_has_changed = 1;

232 memcpy(s->pal, pal, AVPALETTE_SIZE);

233 }

234 /* make the palette available on the way out */

235 memcpy(frame->data[1], s->pal, AVPALETTE_SIZE);

236

237 *got_frame = 1;

238

239 /* report that the buffer was completely consumed */

240 return buf_size;

241 }

242

243 AVCodec ff_idcin_decoder = {

244 .name = "idcinvideo",

245 .long_name = NULL_IF_CONFIG_SMALL("id Quake II CIN video"),

246 .type = AVMEDIA_TYPE_VIDEO,

247 .id = AV_CODEC_ID_IDCIN,

248 .priv_data_size = sizeof(IdcinContext),

249 .init = idcin_decode_init,

250 .decode = idcin_decode_frame,

251 .capabilities = CODEC_CAP_DR1,

252 };

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