FFmpeg
av1_parse.h
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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  */
20 
21 #ifndef AVCODEC_AV1_PARSE_H
22 #define AVCODEC_AV1_PARSE_H
23 
24 #include <limits.h>
25 #include <stdint.h>
26 
27 #include "libavutil/common.h"
28 #include "libavutil/error.h"
29 #include "libavutil/intmath.h"
30 
31 #include "av1.h"
32 #include "get_bits.h"
33 
34 // OBU header fields + max leb128 length
35 #define MAX_OBU_HEADER_SIZE (2 + 8)
36 
37 typedef struct AV1OBU {
38  /** Size of payload */
39  int size;
40  const uint8_t *data;
41 
42  /**
43  * Size, in bits, of just the data, excluding the trailing_one_bit and
44  * any trailing padding.
45  */
46  int size_bits;
47 
48  /** Size of entire OBU, including header */
49  int raw_size;
50  const uint8_t *raw_data;
51 
52  /** GetBitContext initialized to the start of the payload */
54 
55  int type;
56 
59 } AV1OBU;
60 
61 /** An input packet split into OBUs */
62 typedef struct AV1Packet {
64  int nb_obus;
67 } AV1Packet;
68 
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);
78 
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);
88 
89 /**
90  * Free all the allocated memory in the packet.
91  */
93 
94 static inline int64_t leb128(GetBitContext *gb) {
95  int64_t ret = 0;
96  int i;
97 
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)
Definition: get_bits.h:220
AV1OBU
Definition: av1_parse.h:37
ff_av1_extract_obu
int ff_av1_extract_obu(AV1OBU *obu, const uint8_t *buf, int length, void *logctx)
Extract an OBU from a raw bitstream.
Definition: av1_parse.c:29
AV1OBU::data
const uint8_t * data
Definition: av1_parse.h:40
skip_bits
static void skip_bits(GetBitContext *s, int n)
Definition: get_bits.h:468
get_bits
static unsigned int get_bits(GetBitContext *s, int n)
Read 1-25 bits.
Definition: get_bits.h:380
AV1Packet
An input packet split into OBUs.
Definition: av1_parse.h:62
GetBitContext
Definition: get_bits.h:62
type
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf type
Definition: writing_filters.txt:86
pkt
AVPacket * pkt
Definition: movenc.c:59
init_get_bits8
static int init_get_bits8(GetBitContext *s, const uint8_t *buffer, int byte_size)
Initialize GetBitContext.
Definition: get_bits.h:678
parse_obu_header
static int parse_obu_header(const uint8_t *buf, int buf_size, int64_t *obu_size, int *start_pos, int *type, int *temporal_id, int *spatial_id)
Definition: av1_parse.h:107
get_bits.h
limits.h
AV1OBU::gb
GetBitContext gb
GetBitContext initialized to the start of the payload.
Definition: av1_parse.h:53
get_bits1
static unsigned int get_bits1(GetBitContext *s)
Definition: get_bits.h:499
AV1_OBU_TILE_GROUP
@ AV1_OBU_TILE_GROUP
Definition: av1.h:33
error.h
AV1Packet::nb_obus
int nb_obus
Definition: av1_parse.h:64
AV1_OBU_FRAME
@ AV1_OBU_FRAME
Definition: av1.h:35
get_obu_bit_length
static int get_obu_bit_length(const uint8_t *buf, int size, int type)
Definition: av1_parse.h:151
size
int size
Definition: twinvq_data.h:10344
av1.h
AV1OBU::raw_size
int raw_size
Size of entire OBU, including header.
Definition: av1_parse.h:49
skip_bits1
static void skip_bits1(GetBitContext *s)
Definition: get_bits.h:539
AV1OBU::size_bits
int size_bits
Size, in bits, of just the data, excluding the trailing_one_bit and any trailing padding.
Definition: av1_parse.h:46
AV1Packet::obus_allocated_size
unsigned obus_allocated_size
Definition: av1_parse.h:66
i
int i
Definition: input.c:406
common.h
AV1OBU::spatial_id
int spatial_id
Definition: av1_parse.h:58
AV1OBU::raw_data
const uint8_t * raw_data
Definition: av1_parse.h:50
FFMIN
#define FFMIN(a, b)
Definition: macros.h:49
AV1OBU::temporal_id
int temporal_id
Definition: av1_parse.h:57
ret
ret
Definition: filter_design.txt:187
AV1_OBU_TILE_LIST
@ AV1_OBU_TILE_LIST
Definition: av1.h:37
ff_av1_packet_split
int ff_av1_packet_split(AV1Packet *pkt, const uint8_t *buf, int length, void *logctx)
Split an input packet into OBUs.
Definition: av1_parse.c:56
AV1OBU::type
int type
Definition: av1_parse.h:55
AVERROR_INVALIDDATA
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:61
AV1Packet::obus
AV1OBU * obus
Definition: av1_parse.h:63
ff_av1_packet_uninit
void ff_av1_packet_uninit(AV1Packet *pkt)
Free all the allocated memory in the packet.
Definition: av1_parse.c:106
MAX_OBU_HEADER_SIZE
#define MAX_OBU_HEADER_SIZE
Definition: av1_parse.h:35
AV1Packet::obus_allocated
int obus_allocated
Definition: av1_parse.h:65
intmath.h