FFmpeg: libavcodec/dirac_parser.c Source File

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libavcodec

dirac_parser.c

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1 /*

2 * Dirac parser

3 *

6 *

7 * This file is part of FFmpeg.

8 *

9 * FFmpeg is free software; you can redistribute it and/or

10 * modify it under the terms of the GNU Lesser General Public

11 * License as published by the Free Software Foundation; either

12 * version 2.1 of the License, or (at your option) any later version.

13 *

14 * FFmpeg is distributed in the hope that it will be useful,

15 * but WITHOUT ANY WARRANTY; without even the implied warranty of

16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

17 * Lesser General Public License for more details.

18 *

19 * You should have received a copy of the GNU Lesser General Public

20 * License along with FFmpeg; if not, write to the Free Software

21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

22 */

24 /**

25 * @file

26 * Dirac Parser

27 * @author Marco Gerards <marco@gnu.org>

28 */

30 #include <string.h>

32 #include "libavutil/intreadwrite.h"

33 #include "libavutil/mem.h"

34 #include "parser.h"

36 #define DIRAC_PARSE_INFO_PREFIX 0x42424344

38 /**

39 * Find the end of the current frame in the bitstream.

40 * @return the position of the first byte of the next frame or -1

41 */

42 typedef struct DiracParseContext {

43 int state;

44 int is_synced;

45 int sync_offset;

46 int header_bytes_needed;

47 int overread_index;

48 int buffer_size;

49 int index;

50 uint8_t *buffer;

51 int dirac_unit_size;

52 uint8_t *dirac_unit;

53 } DiracParseContext;

55 static int find_frame_end(DiracParseContext *pc,

56 const uint8_t *buf, int buf_size)

57 {

58 uint32_t state = pc->state;

59 int i = 0;

61 if (!pc->is_synced) {

62 for (i = 0; i < buf_size; i++) {

63 state = (state << 8) | buf[i];

64 if (state == DIRAC_PARSE_INFO_PREFIX) {

65 state = -1;

66 pc->is_synced = 1;

67 pc->header_bytes_needed = 9;

68 pc->sync_offset = i;

69 break;

70 }

71 }

72 }

74 if (pc->is_synced) {

75 pc->sync_offset = 0;

76 for (; i < buf_size; i++) {

77 if (state == DIRAC_PARSE_INFO_PREFIX) {

78 if ((buf_size-i) >= pc->header_bytes_needed) {

79 pc->state = -1;

80 return i + pc->header_bytes_needed;

81 } else {

82 pc->header_bytes_needed = 9-(buf_size-i);

83 break;

84 }

85 } else

86 state = (state << 8) | buf[i];

87 }

88 }

89 pc->state = state;

90 return -1;

91 }

93 typedef struct DiracParseUnit

94 {

95 int next_pu_offset;

96 int prev_pu_offset;

97 uint8_t pu_type;

98 } DiracParseUnit;

100 static int unpack_parse_unit(DiracParseUnit *pu, DiracParseContext *pc,

101 int offset)

102 {

103 uint8_t *start = pc->buffer + offset;

104 uint8_t *end = pc->buffer + pc->index;

105 if (start < pc->buffer || (start+13 > end))

106 return 0;

107 pu->pu_type = start[4];

108

109 pu->next_pu_offset = AV_RB32(start+5);

110 pu->prev_pu_offset = AV_RB32(start+9);

111

112 if (pu->pu_type == 0x10 && pu->next_pu_offset == 0)

113 pu->next_pu_offset = 13;

114

115 return 1;

116 }

117

118 static int dirac_combine_frame(AVCodecParserContext *s, AVCodecContext *avctx,

119 int next, const uint8_t **buf, int *buf_size)

120 {

121 int parse_timing_info = (s->pts == AV_NOPTS_VALUE &&

122 s->dts == AV_NOPTS_VALUE);

123 DiracParseContext *pc = s->priv_data;

124

125 if (pc->overread_index) {

126 memcpy(pc->buffer, pc->buffer + pc->overread_index,

127 pc->index - pc->overread_index);

128 pc->index -= pc->overread_index;

129 pc->overread_index = 0;

130 if (*buf_size == 0 && pc->buffer[4] == 0x10) {

131 *buf = pc->buffer;

132 *buf_size = pc->index;

133 return 0;

134 }

135 }

136

137 if ( next == -1) {

138 /* Found a possible frame start but not a frame end */

139 void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,

140 pc->index + (*buf_size -

141 pc->sync_offset));

142 pc->buffer = new_buffer;

143 memcpy(pc->buffer+pc->index, (*buf + pc->sync_offset),

144 *buf_size - pc->sync_offset);

145 pc->index += *buf_size - pc->sync_offset;

146 return -1;

147 } else {

148 /* Found a possible frame start and a possible frame end */

149 DiracParseUnit pu1, pu;

150 void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,

151 pc->index + next);

152 pc->buffer = new_buffer;

153 memcpy(pc->buffer + pc->index, *buf, next);

154 pc->index += next;

155

156 /* Need to check if we have a valid Parse Unit. We can't go by the

157 * sync pattern 'BBCD' alone because arithmetic coding of the residual

158 * and motion data can cause the pattern triggering a false start of

159 * frame. So check if the previous parse offset of the next parse unit

160 * is equal to the next parse offset of the current parse unit then

161 * we can be pretty sure that we have a valid parse unit */

162 if (!unpack_parse_unit(&pu1, pc, pc->index - 13) ||

163 !unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) ||

164 pu.next_pu_offset != pu1.prev_pu_offset ||

165 pc->index < pc->dirac_unit_size + 13LL + pu1.prev_pu_offset

166 ) {

167 pc->index -= 9;

168 *buf_size = next-9;

169 pc->header_bytes_needed = 9;

170 return -1;

171 }

172

173 /* All non-frame data must be accompanied by frame data. This is to

174 * ensure that pts is set correctly. So if the current parse unit is

175 * not frame data, wait for frame data to come along */

176

177 pc->dirac_unit = pc->buffer + pc->index - 13 -

178 pu1.prev_pu_offset - pc->dirac_unit_size;

179

180 pc->dirac_unit_size += pu.next_pu_offset;

181

182 if ((pu.pu_type&0x08) != 0x08) {

183 pc->header_bytes_needed = 9;

184 *buf_size = next;

185 return -1;

186 }

187

188 /* Get the picture number to set the pts and dts*/

189 if (parse_timing_info) {

190 uint8_t *cur_pu = pc->buffer +

191 pc->index - 13 - pu1.prev_pu_offset;

192 int pts = AV_RB32(cur_pu + 13);

193 if (s->last_pts == 0 && s->last_dts == 0)

194 s->dts = pts - 1;

195 else

196 s->dts = s->last_dts+1;

197 s->pts = pts;

198 if (!avctx->has_b_frames && (cur_pu[4] & 0x03))

199 avctx->has_b_frames = 1;

200 }

201 if (avctx->has_b_frames && s->pts == s->dts)

202 s->pict_type = AV_PICTURE_TYPE_B;

203

204 /* Finally have a complete Dirac data unit */

205 *buf = pc->dirac_unit;

206 *buf_size = pc->dirac_unit_size;

207

208 pc->dirac_unit_size = 0;

209 pc->overread_index = pc->index-13;

210 pc->header_bytes_needed = 9;

211 }

212 return next;

213 }

214

215 static int dirac_parse(AVCodecParserContext *s, AVCodecContext *avctx,

216 const uint8_t **poutbuf, int *poutbuf_size,

217 const uint8_t *buf, int buf_size)

218 {

219 DiracParseContext *pc = s->priv_data;

220 int next;

221

222 *poutbuf = NULL;

223 *poutbuf_size = 0;

224

225 if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {

226 next = buf_size;

227 *poutbuf = buf;

228 *poutbuf_size = buf_size;

229 /* Assume that data has been packetized into an encapsulation unit. */

230 } else {

231 next = find_frame_end(pc, buf, buf_size);

232 if (!pc->is_synced && next == -1) {

233 /* No frame start found yet. So throw away the entire buffer. */

234 return buf_size;

235 }

236

237 if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0) {

238 return buf_size;

239 }

240 }

241

242 *poutbuf = buf;

243 *poutbuf_size = buf_size;

244 return next;

245 }

246

247 static void dirac_parse_close(AVCodecParserContext *s)

248 {

249 DiracParseContext *pc = s->priv_data;

250

251 if (pc->buffer_size > 0)

252 av_free(pc->buffer);

253 }

254

255 AVCodecParser ff_dirac_parser = {

256 .codec_ids = { AV_CODEC_ID_DIRAC },

257 .priv_data_size = sizeof(DiracParseContext),

258 .parser_parse = dirac_parse,

259 .parser_close = dirac_parse_close,

260 };

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