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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
  33.     AVCodecParserContext   *parser;
  34.     int64_t                 last_IP_pts;
  35.     int64_t                 cur_dts;
  36.     int64_t                 reference_dts;
  37.     int                     probe_packets;
  38. } AVParserStreamState;
  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)
  55. } AVParserState;
  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.  */
  79. int64_t ff_gen_syncpoint_search(AVFormatContext *s,
  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.  */
  101. AVParserState *ff_store_parser_state(AVFormatContext *s);
  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.  */
  113. void ff_restore_parser_state(AVFormatContext *s, AVParserState *state);
  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.  */
  121. void ff_free_parser_state(AVFormatContext *s, AVParserState *state);
  122.  
  123. #endif /* AVFORMAT_SEEK_H */
  124.