xref: /third_party/ffmpeg/libavcodec/av1_parse.h (revision cabdff1a) 
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/error.h"
28#include "libavutil/intmath.h"
29#include "libavutil/macros.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
37typedef 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 */
53    GetBitContext gb;
54
55    int type;
56
57    int temporal_id;
58    int spatial_id;
59} AV1OBU;
60
61/** An input packet split into OBUs */
62typedef struct AV1Packet {
63    AV1OBU *obus;
64    int nb_obus;
65    int obus_allocated;
66    unsigned obus_allocated_size;
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 */
76int 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 */
86int 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 */
92void ff_av1_packet_uninit(AV1Packet *pkt);
93
94static 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
107static 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
151static 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 */
185