libavformat/seek.h

   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
  33     AVCodecParserContext   *parser;
  34     AVPacket                cur_pkt;
  35     int64_t                 last_IP_pts;
  36     int64_t                 cur_dts;
  37     int64_t                 reference_dts;
  38     const uint8_t          *cur_ptr;
  39     int                     cur_len;
  40     int                     probe_packets;
  41 } AVParserStreamState;
  42
  43 /**
  44  * structure to store parser state of AVFormat
  45  */
  46 typedef struct AVParserState {
  47     int64_t         fpos;                   ///< file position at the time of call
  48
  49     // saved members of AVFormatContext
  50     AVStream       *cur_st;                 ///< current stream.
  51     AVPacketList   *packet_buffer;          ///< packet buffer of original state
  52     AVPacketList   *raw_packet_buffer;      ///< raw packet buffer of original state
  53     int raw_packet_buffer_remaining_size;   ///< remaining space in raw_packet_buffer
  54
  55     // saved info for streams
  56     int                  nb_streams;        ///< number of streams with stored state
  57     AVParserStreamState *stream_states;     ///< states of individual streams (array)
  58 } AVParserState;
  59
  60 /**
  61  * Search for the sync point of all active streams.
  62  *
  63  * This routine is not supposed to be called directly by a user application,
  64  * but by demuxers.
  65  *
  66  * A sync point is defined as a point in stream, such that, when decoding start
  67  * from this point, the decoded output of all streams synchronizes closest
  68  * to the given timestamp ts. This routine also takes timestamp limits into account.
  69  * Thus, the output will synchronize no sooner than ts_min and no later than ts_max.
  70  *
  71  * @param stream_index stream index for time base reference of timestamps
  72  * @param pos          approximate position where to start searching for key frames
  73  * @param min_ts       minimum allowed timestamp (position, if AVSEEK_FLAG_BYTE set)
  74  * @param ts           target timestamp (or position, if AVSEEK_FLAG_BYTE set in flags)
  75  * @param max_ts       maximum allowed timestamp (position, if AVSEEK_FLAG_BYTE set)
  76  * @param flags        if AVSEEK_FLAG_ANY is set, seek to any frame, otherwise only
  77  *                     to a keyframe. If AVSEEK_FLAG_BYTE is set, search by
  78  *                     position, not by timestamp.
  79  * @return -1 if no such sync point could be found, otherwise stream position
  80  *                     (stream is repositioned to this position)
  81  */
  82 int64_t ff_gen_syncpoint_search(AVFormatContext *s,
  83                                 int stream_index,
  84                                 int64_t pos,
  85                                 int64_t min_ts,
  86                                 int64_t ts,
  87                                 int64_t max_ts,
  88                                 int flags);
  89
  90 /**
  91  * Store current parser state and file position.
  92  *
  93  * This function can be used by demuxers before a destructive seeking algorithm
  94  * to store the parser state. Depending on the outcome of the seek, either the original
  95  * state can be restored or the new state kept and the original state freed.
  96  *
  97  * @note As a side effect, the original parser state is reset, since structures
  98  *       are relinked to the stored state instead of being deeply-copied (for
  99  *       performance reasons and to keep the code simple).
 100  *
 101  * @param s context from which to save state
 102  * @return parser state object or NULL if memory could not be allocated
 103  */
 104 AVParserState *ff_store_parser_state(AVFormatContext *s);
 105
 106 /**
 107  * Restore previously saved parser state and file position.
 108  *
 109  * Saved state will be invalidated and freed by this call, since internal
 110  * structures will be relinked back to the stored state instead of being
 111  * deeply-copied.
 112  *
 113  * @param s     context to which to restore state (same as used for storing state)
 114  * @param state state to restore
 115  */
 116 void ff_restore_parser_state(AVFormatContext *s, AVParserState *state);
 117
 118 /**
 119  * Free previously saved parser state.
 120  *
 121  * @param s     context to which the state belongs (same as used for storing state)
 122  * @param state state to free
 123  */
 124 void ff_free_parser_state(AVFormatContext *s, AVParserState *state);
 125
 126 #endif /* AVFORMAT_SEEK_H */