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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;
38 
39 /**
40  * structure to store parser state of AVFormat
41  */
42 typedef struct AVParserState {
43  int64_t fpos; ///< file position at the time of call
44 
45  // saved members of AVFormatContext
46  AVPacketList *packet_buffer; ///< packet buffer of original state
47  AVPacketList *parse_queue; ///< parse queue of original state
48  AVPacketList *raw_packet_buffer; ///< raw packet buffer of original state
49  int raw_packet_buffer_remaining_size; ///< remaining space in raw_packet_buffer
50 
51  // saved info for streams
52  int nb_streams; ///< number of streams with stored state
53  AVParserStreamState *stream_states; ///< states of individual streams (array)
55 
56 /**
57  * Search for the sync point of all active streams.
58  *
59  * This routine is not supposed to be called directly by a user application,
60  * but by demuxers.
61  *
62  * A sync point is defined as a point in stream, such that, when decoding start
63  * from this point, the decoded output of all streams synchronizes closest
64  * to the given timestamp ts. This routine also takes timestamp limits into account.
65  * Thus, the output will synchronize no sooner than ts_min and no later than ts_max.
66  *
67  * @param stream_index stream index for time base reference of timestamps
68  * @param pos approximate position where to start searching for key frames
69  * @param min_ts minimum allowed timestamp (position, if AVSEEK_FLAG_BYTE set)
70  * @param ts target timestamp (or position, if AVSEEK_FLAG_BYTE set in flags)
71  * @param max_ts maximum allowed timestamp (position, if AVSEEK_FLAG_BYTE set)
72  * @param flags if AVSEEK_FLAG_ANY is set, seek to any frame, otherwise only
73  * to a keyframe. If AVSEEK_FLAG_BYTE is set, search by
74  * position, not by timestamp.
75  * @return -1 if no such sync point could be found, otherwise stream position
76  * (stream is repositioned to this position)
77  */
79  int stream_index,
80  int64_t pos,
81  int64_t min_ts,
82  int64_t ts,
83  int64_t max_ts,
84  int flags);
85 
86 /**
87  * Store current parser state and file position.
88  *
89  * This function can be used by demuxers before a destructive seeking algorithm
90  * to store the parser state. Depending on the outcome of the seek, either the original
91  * state can be restored or the new state kept and the original state freed.
92  *
93  * @note As a side effect, the original parser state is reset, since structures
94  * are relinked to the stored state instead of being deeply-copied (for
95  * performance reasons and to keep the code simple).
96  *
97  * @param s context from which to save state
98  * @return parser state object or NULL if memory could not be allocated
99  */
101 
102 /**
103  * Restore previously saved parser state and file position.
104  *
105  * Saved state will be invalidated and freed by this call, since internal
106  * structures will be relinked back to the stored state instead of being
107  * deeply-copied.
108  *
109  * @param s context to which to restore state (same as used for storing state)
110  * @param state state to restore
111  */
113 
114 /**
115  * Free previously saved parser state.
116  *
117  * @param s context to which the state belongs (same as used for storing state)
118  * @param state state to free
119  */
121 
122 #endif /* AVFORMAT_SEEK_H */