libavformat/seek.h

   1 /*
   2  * Utility functions for seeking for use within FFmpeg 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 /// Opaque structure for parser state.
  29 typedef struct AVParserState AVParserState;
  30
  31 /**
  32  * Search for sync point of all active streams.
  33  *
  34  * This is not supposed to be called directly by a user application,
  35  * but by demuxers.
  36  *
  37  * A sync point is a point in stream, so that decoding from this point,
  38  * output of decoders of all streams synchronizes closest to given timestamp
  39  * ts (but taking timestamp limits into account, i.e., no sooner than ts_min
  40  * and no later than ts_max).
  41  *
  42  * @param stream_index stream index for time base reference of timestamps.
  43  * @param pos approximate position where to start searching for key frames.
  44  * @param min_ts minimum allowed timestamp (position, if AVSEEK_FLAG_BYTE set).
  45  * @param ts target timestamp (or position, if AVSEEK_FLAG_BYTE set in flags).
  46  * @param max_ts maximum allowed timestamp (position, if AVSEEK_FLAG_BYTE set).
  47  * @param flags if AVSEEK_FLAG_ANY is set, seek to any frame, otherwise only
  48  *              to a keyframe. If AVSEEK_FLAG_BYTE is set, search by
  49  *              position, not by timestamp.
  50  * @return < 0 if no such sync point could be found, otherwise stream position
  51  *              (stream is repositioned to this position).
  52  */
  53 int64_t ff_gen_syncpoint_search(AVFormatContext *s,
  54                                 int stream_index,
  55                                 int64_t pos,
  56                                 int64_t min_ts,
  57                                 int64_t ts,
  58                                 int64_t max_ts,
  59                                 int flags);
  60
  61 /**
  62  * Store current parser state and file position.
  63  *
  64  * This function can be used by demuxers before destructive seeking algorithm
  65  * to store parser state. After the seek, depending on outcome, original state
  66  * can be restored or new state kept and original state freed.
  67  *
  68  * @note As a side effect, original parser state is reset, since structures
  69  *       are relinked to stored state instead of being deeply-copied (for
  70  *       performance reasons and to keep code simple).
  71  *
  72  * @param s context from which to save state.
  73  * @return parser state object or NULL if memory could not be allocated.
  74  */
  75 AVParserState *ff_store_parser_state(AVFormatContext *s);
  76
  77 /**
  78  * Restore previously saved parser state and file position.
  79  *
  80  * Saved state will be invalidated and freed by this call, since internal
  81  * structures will be relinked back to stored state instead of being
  82  * deeply-copied.
  83  *
  84  * @param s context to which to restore state (same as used for storing state).
  85  * @param state state to restore.
  86  */
  87 void ff_restore_parser_state(AVFormatContext *s, AVParserState *state);
  88
  89 /**
  90  * Free previously saved parser state.
  91  *
  92  * @param s context to which the state belongs (same as used for storing state).
  93  * @param state state to free.
  94  */
  95 void ff_free_parser_state(AVFormatContext *s, AVParserState *state);
  96
  97 #endif /* AVFORMAT_SEEK_H */