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seek.h
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1 /*
2  * seek utility functions for use within format handlers
3  *
4  * Copyright (c) 2009 Ivan Schreter
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  */
22 
23 #ifndef AVFORMAT_SEEK_H
24 #define AVFORMAT_SEEK_H
25 
26 #include "avformat.h"
27 
28 /**
29  * structure to store parser state of one AVStream
30  */
31 typedef struct AVParserStreamState {
32  // saved members of AVStream
34  int64_t last_IP_pts;
35  int64_t cur_dts;
36  int64_t reference_dts;
39 
40 /**
41  * structure to store parser state of AVFormat
42  */
43 typedef struct AVParserState {
44  int64_t fpos; ///< file position at the time of call
45 
46  // saved members of AVFormatContext
47  AVPacketList *packet_buffer; ///< packet buffer of original state
48  AVPacketList *parse_queue; ///< parse queue of original state
49  AVPacketList *raw_packet_buffer; ///< raw packet buffer of original state
50  int raw_packet_buffer_remaining_size; ///< remaining space in raw_packet_buffer
51 
52  // saved info for streams
53  int nb_streams; ///< number of streams with stored state
54  AVParserStreamState *stream_states; ///< states of individual streams (array)
56 
57 /**
58  * Search for the sync point of all active streams.
59  *
60  * This routine is not supposed to be called directly by a user application,
61  * but by demuxers.
62  *
63  * A sync point is defined as a point in stream, such that, when decoding start
64  * from this point, the decoded output of all streams synchronizes closest
65  * to the given timestamp ts. This routine also takes timestamp limits into account.
66  * Thus, the output will synchronize no sooner than ts_min and no later than ts_max.
67  *
68  * @param stream_index stream index for time base reference of timestamps
69  * @param pos approximate position where to start searching for key frames
70  * @param min_ts minimum allowed timestamp (position, if AVSEEK_FLAG_BYTE set)
71  * @param ts target timestamp (or position, if AVSEEK_FLAG_BYTE set in flags)
72  * @param max_ts maximum allowed timestamp (position, if AVSEEK_FLAG_BYTE set)
73  * @param flags if AVSEEK_FLAG_ANY is set, seek to any frame, otherwise only
74  * to a keyframe. If AVSEEK_FLAG_BYTE is set, search by
75  * position, not by timestamp.
76  * @return -1 if no such sync point could be found, otherwise stream position
77  * (stream is repositioned to this position)
78  */
80  int stream_index,
81  int64_t pos,
82  int64_t min_ts,
83  int64_t ts,
84  int64_t max_ts,
85  int flags);
86 
87 /**
88  * Store current parser state and file position.
89  *
90  * This function can be used by demuxers before a destructive seeking algorithm
91  * to store the parser state. Depending on the outcome of the seek, either the original
92  * state can be restored or the new state kept and the original state freed.
93  *
94  * @note As a side effect, the original parser state is reset, since structures
95  * are relinked to the stored state instead of being deeply-copied (for
96  * performance reasons and to keep the code simple).
97  *
98  * @param s context from which to save state
99  * @return parser state object or NULL if memory could not be allocated
100  */
102 
103 /**
104  * Restore previously saved parser state and file position.
105  *
106  * Saved state will be invalidated and freed by this call, since internal
107  * structures will be relinked back to the stored state instead of being
108  * deeply-copied.
109  *
110  * @param s context to which to restore state (same as used for storing state)
111  * @param state state to restore
112  */
114 
115 /**
116  * Free previously saved parser state.
117  *
118  * @param s context to which the state belongs (same as used for storing state)
119  * @param state state to free
120  */
122 
123 #endif /* AVFORMAT_SEEK_H */