FFmpeg: libavcodec/av1_parse.h Source File

FFmpeg

[フレーム]

libavcodec

av1_parse.h

Go to the documentation of this file.

1 /*

2 * AV1 common parsing code

3 *

4 * This file is part of FFmpeg.

5 *

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

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

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

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

10 *

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

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

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

14 * Lesser General Public License for more details.

15 *

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

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

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

19 */

21 #ifndef AVCODEC_AV1_PARSE_H

22 #define AVCODEC_AV1_PARSE_H

24 #include <limits.h>

25 #include <stdint.h>

27 #include "libavutil/common.h"

28 #include "libavutil/error.h"

29 #include "libavutil/intmath.h"

31 #include "av1.h"

32 #include "get_bits.h"

34 // OBU header fields + max leb128 length

35 #define MAX_OBU_HEADER_SIZE (2 + 8)

37 typedef struct AV1OBU {

38 /** Size of payload */

39 int size;

40 const uint8_t *data;

42 /**

43 * Size, in bits, of just the data, excluding the trailing_one_bit and

44 * any trailing padding.

45 */

46 int size_bits;

48 /** Size of entire OBU, including header */

49 int raw_size;

50 const uint8_t *raw_data;

52 /** GetBitContext initialized to the start of the payload */

53 GetBitContext gb;

55 int type;

57 int temporal_id;

58 int spatial_id;

59 } AV1OBU;

61 /** An input packet split into OBUs */

62 typedef struct AV1Packet {

63 AV1OBU *obus;

64 int nb_obus;

65 int obus_allocated;

66 unsigned obus_allocated_size;

67 } AV1Packet;

69 /**

70 * Extract an OBU from a raw bitstream.

71 *

72 * @note This function does not copy or store any bitstream data. All

73 * the pointers in the AV1OBU structure will be valid as long

74 * as the input buffer also is.

75 */

76 int ff_av1_extract_obu(AV1OBU *obu, const uint8_t *buf, int length,

77 void *logctx);

79 /**

80 * Split an input packet into OBUs.

81 *

82 * @note This function does not copy or store any bitstream data. All

83 * the pointers in the AV1Packet structure will be valid as

84 * long as the input buffer also is.

85 */

86 int ff_av1_packet_split(AV1Packet *pkt, const uint8_t *buf, int length,

87 void *logctx);

89 /**

90 * Free all the allocated memory in the packet.

91 */

92 void ff_av1_packet_uninit(AV1Packet *pkt);

94 static inline int64_t leb128(GetBitContext *gb) {

95 int64_t ret = 0;

96 int i;

98 for (i = 0; i < 8; i++) {

99 int byte = get_bits(gb, 8);

100 ret |= (int64_t)(byte & 0x7f) << (i * 7);

101 if (!(byte & 0x80))

102 break;

103 }

104 return ret;

105 }

106

107 static inline int parse_obu_header(const uint8_t *buf, int buf_size,

108 int64_t *obu_size, int *start_pos, int *type,

109 int *temporal_id, int *spatial_id)

110 {

111 GetBitContext gb;

112 int ret, extension_flag, has_size_flag;

113 int64_t size;

114

115 ret = init_get_bits8(&gb, buf, FFMIN(buf_size, MAX_OBU_HEADER_SIZE));

116 if (ret < 0)

117 return ret;

118

119 if (get_bits1(&gb) != 0) // obu_forbidden_bit

120 return AVERROR_INVALIDDATA;

121

122 *type = get_bits(&gb, 4);

123 extension_flag = get_bits1(&gb);

124 has_size_flag = get_bits1(&gb);

125 skip_bits1(&gb); // obu_reserved_1bit

126

127 if (extension_flag) {

128 *temporal_id = get_bits(&gb, 3);

129 *spatial_id = get_bits(&gb, 2);

130 skip_bits(&gb, 3); // extension_header_reserved_3bits

131 } else {

132 *temporal_id = *spatial_id = 0;

133 }

134

135 *obu_size = has_size_flag ? leb128(&gb)

136 : buf_size - 1 - extension_flag;

137

138 if (get_bits_left(&gb) < 0)

139 return AVERROR_INVALIDDATA;

140

141 *start_pos = get_bits_count(&gb) / 8;

142

143 size = *obu_size + *start_pos;

144

145 if (size > buf_size)

146 return AVERROR_INVALIDDATA;

147

148 return size;

149 }

150

151 static inline int get_obu_bit_length(const uint8_t *buf, int size, int type)

152 {

153 int v;

154

155 /* There are no trailing bits on these */

156 if (type == AV1_OBU_TILE_GROUP ||

157 type == AV1_OBU_TILE_LIST ||

158 type == AV1_OBU_FRAME) {

159 if (size > INT_MAX / 8)

160 return AVERROR(ERANGE);

161 else

162 return size * 8;

163 }

164

165 while (size > 0 && buf[size - 1] == 0)

166 size--;

167

168 if (!size)

169 return 0;

170

171 v = buf[size - 1];

172

173 if (size > INT_MAX / 8)

174 return AVERROR(ERANGE);

175 size *= 8;

176

177 /* Remove the trailing_one_bit and following trailing zeros */

178 if (v)

179 size -= ff_ctz(v) + 1;

180

181 return size;

182 }

183

184 #endif /* AVCODEC_AV1_PARSE_H */

get_bits_left

static int get_bits_left(GetBitContext *gb)

Definition: get_bits.h:850

AVERROR

Filter the word "frame" indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions

AV1OBU::size

int size

Size of payload.

Definition: av1_parse.h:39

ff_ctz

#define ff_ctz

Definition: intmath.h:106

leb128

static int64_t leb128(GetBitContext *gb)

Definition: av1_parse.h:94

get_bits_count

static int get_bits_count(const GetBitContext *s)