FFmpeg: libavcodec/mpeg12.c Source File

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libavcodec

mpeg12.c

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1 /*

2 * MPEG-1/2 decoder

5 *

6 * This file is part of FFmpeg.

7 *

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

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

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

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

12 *

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

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

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

16 * Lesser General Public License for more details.

17 *

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

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

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

21 */

23 /**

24 * @file

25 * MPEG-1/2 decoder

26 */

28 #define UNCHECKED_BITSTREAM_READER 1

30 #include "libavutil/attributes.h"

31 #include "libavutil/avassert.h"

32 #include "libavutil/timecode.h"

34 #include "internal.h"

35 #include "avcodec.h"

36 #include "dsputil.h"

37 #include "mpegvideo.h"

38 #include "error_resilience.h"

39 #include "mpeg12.h"

40 #include "mpeg12data.h"

41 #include "mpeg12decdata.h"

42 #include "bytestream.h"

43 #include "vdpau_internal.h"

44 #include "xvmc_internal.h"

45 #include "thread.h"

47 uint8_t ff_mpeg12_static_rl_table_store[2][2][2*MAX_RUN + MAX_LEVEL + 3];

49 #define INIT_2D_VLC_RL(rl, static_size)\

50 {\

51 static RL_VLC_ELEM rl_vlc_table[static_size];\

52 INIT_VLC_STATIC(&rl.vlc, TEX_VLC_BITS, rl.n + 2,\

53 &rl.table_vlc[0][1], 4, 2,\

54 &rl.table_vlc[0][0], 4, 2, static_size);\

55 \

56 rl.rl_vlc[0] = rl_vlc_table;\

57 init_2d_vlc_rl(&rl);\

58 }

60 static av_cold void init_2d_vlc_rl(RLTable *rl)

61 {

62 int i;

64 for (i = 0; i < rl->vlc.table_size; i++) {

65 int code = rl->vlc.table[i][0];

66 int len = rl->vlc.table[i][1];

67 int level, run;

69 if (len == 0) { // illegal code

70 run = 65;

71 level = MAX_LEVEL;

72 } else if (len<0) { //more bits needed

73 run = 0;

74 level = code;

75 } else {

76 if (code == rl->n) { //esc

77 run = 65;

78 level = 0;

79 } else if (code == rl->n+1) { //eob

80 run = 0;

81 level = 127;

82 } else {

83 run = rl->table_run [code] + 1;

84 level = rl->table_level[code];

85 }

86 }

87 rl->rl_vlc[0][i].len = len;

88 rl->rl_vlc[0][i].level = level;

89 rl->rl_vlc[0][i].run = run;

90 }

91 }

93 av_cold void ff_mpeg12_common_init(MpegEncContext *s)

94 {

96 s->y_dc_scale_table =

97 s->c_dc_scale_table = ff_mpeg2_dc_scale_table[s->intra_dc_precision];

99 }

100

101 void ff_mpeg1_clean_buffers(MpegEncContext *s)

102 {

103 s->last_dc[0] = 1 << (7 + s->intra_dc_precision);

104 s->last_dc[1] = s->last_dc[0];

105 s->last_dc[2] = s->last_dc[0];

106 memset(s->last_mv, 0, sizeof(s->last_mv));

107 }

108

109

110 /******************************************/

111 /* decoding */

112

113 VLC ff_mv_vlc;

114

115 VLC ff_dc_lum_vlc;

116 VLC ff_dc_chroma_vlc;

117

118 VLC ff_mbincr_vlc;

119 VLC ff_mb_ptype_vlc;

120 VLC ff_mb_btype_vlc;

121 VLC ff_mb_pat_vlc;

122

123 av_cold void ff_mpeg12_init_vlcs(void)

124 {

125 static int done = 0;

126

127 if (!done) {

128 done = 1;

129

130 INIT_VLC_STATIC(&ff_dc_lum_vlc, DC_VLC_BITS, 12,

131 ff_mpeg12_vlc_dc_lum_bits, 1, 1,

132 ff_mpeg12_vlc_dc_lum_code, 2, 2, 512);

133 INIT_VLC_STATIC(&ff_dc_chroma_vlc, DC_VLC_BITS, 12,

134 ff_mpeg12_vlc_dc_chroma_bits, 1, 1,

135 ff_mpeg12_vlc_dc_chroma_code, 2, 2, 514);

136 INIT_VLC_STATIC(&ff_mv_vlc, MV_VLC_BITS, 17,

137 &ff_mpeg12_mbMotionVectorTable[0][1], 2, 1,

138 &ff_mpeg12_mbMotionVectorTable[0][0], 2, 1, 518);

139 INIT_VLC_STATIC(&ff_mbincr_vlc, MBINCR_VLC_BITS, 36,

140 &ff_mpeg12_mbAddrIncrTable[0][1], 2, 1,

141 &ff_mpeg12_mbAddrIncrTable[0][0], 2, 1, 538);

142 INIT_VLC_STATIC(&ff_mb_pat_vlc, MB_PAT_VLC_BITS, 64,

143 &ff_mpeg12_mbPatTable[0][1], 2, 1,

144 &ff_mpeg12_mbPatTable[0][0], 2, 1, 512);

145

146 INIT_VLC_STATIC(&ff_mb_ptype_vlc, MB_PTYPE_VLC_BITS, 7,

147 &table_mb_ptype[0][1], 2, 1,

148 &table_mb_ptype[0][0], 2, 1, 64);

149 INIT_VLC_STATIC(&ff_mb_btype_vlc, MB_BTYPE_VLC_BITS, 11,

150 &table_mb_btype[0][1], 2, 1,

151 &table_mb_btype[0][0], 2, 1, 64);

152 ff_init_rl(&ff_rl_mpeg1, ff_mpeg12_static_rl_table_store[0]);

153 ff_init_rl(&ff_rl_mpeg2, ff_mpeg12_static_rl_table_store[1]);

154

155 INIT_2D_VLC_RL(ff_rl_mpeg1, 680);

156 INIT_2D_VLC_RL(ff_rl_mpeg2, 674);

157 }

158 }

159

160 /**

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

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

163 */

164 int ff_mpeg1_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size, AVCodecParserContext *s)

165 {

166 int i;

167 uint32_t state = pc->state;

168

169 /* EOF considered as end of frame */

170 if (buf_size == 0)

171 return 0;

172

173 /*

174 0 frame start -> 1/4

175 1 first_SEQEXT -> 0/2

176 2 first field start -> 3/0

177 3 second_SEQEXT -> 2/0

178 4 searching end

179 */

180

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

182 av_assert1(pc->frame_start_found >= 0 && pc->frame_start_found <= 4);

183 if (pc->frame_start_found & 1) {

184 if (state == EXT_START_CODE && (buf[i] & 0xF0) != 0x80)

185 pc->frame_start_found--;

186 else if (state == EXT_START_CODE + 2) {

187 if ((buf[i] & 3) == 3)

188 pc->frame_start_found = 0;

189 else

190 pc->frame_start_found = (pc->frame_start_found + 1) & 3;

191 }

192 state++;

193 } else {

194 i = avpriv_find_start_code(buf + i, buf + buf_size, &state) - buf - 1;

195 if (pc->frame_start_found == 0 && state >= SLICE_MIN_START_CODE && state <= SLICE_MAX_START_CODE) {

196 i++;

197 pc->frame_start_found = 4;

198 }

199 if (state == SEQ_END_CODE) {

200 pc->frame_start_found = 0;

201 pc->state=-1;

202 return i+1;

203 }

204 if (pc->frame_start_found == 2 && state == SEQ_START_CODE)

205 pc->frame_start_found = 0;

206 if (pc->frame_start_found < 4 && state == EXT_START_CODE)

207 pc->frame_start_found++;

208 if (pc->frame_start_found == 4 && (state & 0xFFFFFF00) == 0x100) {

209 if (state < SLICE_MIN_START_CODE || state > SLICE_MAX_START_CODE) {

210 pc->frame_start_found = 0;

211 pc->state = -1;

212 return i - 3;

213 }

214 }

215 if (pc->frame_start_found == 0 && s && state == PICTURE_START_CODE) {

216 ff_fetch_timestamp(s, i - 3, 1);

217 }

218 }

219 }

220 pc->state = state;

221 return END_NOT_FOUND;

222 }

223

Generated on Wed Jul 10 2013 23:48:01 for FFmpeg by doxygen 1.8.2