libextractor

GNU libextractor
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mediaffmpeg.h (4302B)

      1 /*
      2      This file is part of libextractor.
      3      Copyright (C) 2026 Vidyut Samanta and Christian Grothoff
      4 
      5      libextractor is free software; you can redistribute it and/or modify
      6      it under the terms of the GNU General Public License as published
      7      by the Free Software Foundation; either version 3, or (at your
      8      option) any later version.
      9 
     10      libextractor is distributed in the hope that it will be useful, but
     11      WITHOUT ANY WARRANTY; without even the implied warranty of
     12      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     13      General Public License for more details.
     14 
     15      You should have received a copy of the GNU General Public License
     16      along with libextractor; see the file COPYING.  If not, write to the
     17      Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
     18      Boston, MA 02110-1301, USA.
     19  */
     20 /**
     21  * @file plugins/mediaffmpeg.h
     22  * @brief plumbing between an extraction context and FFmpeg's demuxer
     23  * @author Christian Grothoff
     24  *
     25  * Shared by thumbnailffmpeg and previewopus.  Requires FFmpeg 5.1 or
     26  * newer; there is deliberately no compatibility code for older versions.
     27  */
     28 #ifndef MEDIAFFMPEG_H
     29 #define MEDIAFFMPEG_H
     30 
     31 #include "extractor.h"
     32 #include "mediautil.h"
     33 
     34 #include <libavcodec/avcodec.h>
     35 #include <libavformat/avformat.h>
     36 #include <libavutil/avutil.h>
     37 
     38 /**
     39  * Size of the buffer we give to the AVIOContext.  Small on purpose: each
     40  * refill turns into a read on the extraction context, which is what keeps
     41  * the IPC channel from looking hung to the parent process (which kills
     42  * plugins that stay silent for 500ms).
     43  */
     44 #define EXTRACTOR_FFMPEG_AVIO_BUFFER (16 * 1024)
     45 
     46 /**
     47  * Do not look at more than this much data to identify the streams.
     48  */
     49 #define EXTRACTOR_FFMPEG_PROBE_SIZE (1024 * 1024)
     50 
     51 /**
     52  * Do not spend more than this much media time on stream analysis.
     53  */
     54 #define EXTRACTOR_FFMPEG_MAX_ANALYZE (2 * AV_TIME_BASE)
     55 
     56 
     57 /**
     58  * State of an FFmpeg demuxer reading from an extraction context.
     59  */
     60 struct EXTRACTOR_FFmpegIO
     61 {
     62   /**
     63    * Extraction context we are reading from.
     64    */
     65   struct EXTRACTOR_ExtractContext *ec;
     66 
     67   /**
     68    * When we have to give up.
     69    */
     70   struct EXTRACTOR_MediaDeadline deadline;
     71 
     72   /**
     73    * Format context, NULL if not open.
     74    */
     75   AVFormatContext *fmt;
     76 
     77   /**
     78    * I/O context wrapping @e ec.
     79    */
     80   AVIOContext *avio;
     81 };
     82 
     83 
     84 /**
     85  * Open the input of @a io->ec with FFmpeg and identify its streams.
     86  * @a io->ec and @a io->deadline must already be set.
     87  *
     88  * @param[in,out] io I/O state to complete
     89  * @return 0 on success
     90  */
     91 int
     92 EXTRACTOR_ffmpeg_open_ (struct EXTRACTOR_FFmpegIO *io);
     93 
     94 
     95 /**
     96  * Close what EXTRACTOR_ffmpeg_open_() opened.
     97  *
     98  * @param[in,out] io I/O state to clean up
     99  */
    100 void
    101 EXTRACTOR_ffmpeg_close_ (struct EXTRACTOR_FFmpegIO *io);
    102 
    103 
    104 /**
    105  * Close @a io, rewind the extraction context and open it again, so that
    106  * the next av_read_frame() starts at the beginning of the file with
    107  * fresh demuxer state (and no stream discarded).
    108  *
    109  * @param[in,out] io I/O state to reopen
    110  * @return 0 on success; on failure @a io is closed
    111  */
    112 int
    113 EXTRACTOR_ffmpeg_reopen_ (struct EXTRACTOR_FFmpegIO *io);
    114 
    115 
    116 /**
    117  * Find the best stream of @a type and open a decoder for it.
    118  *
    119  * @param io open I/O state
    120  * @param type media type to look for
    121  * @param[out] ctx set to the open decoder
    122  * @return index of the stream, or a negative value on error
    123  */
    124 int
    125 EXTRACTOR_ffmpeg_open_stream_ (struct EXTRACTOR_FFmpegIO *io,
    126                                enum AVMediaType type,
    127                                AVCodecContext **ctx);
    128 
    129 
    130 /**
    131  * Determine where in the media we should sample, honouring both the
    132  * requested offset and the (possibly unknown) duration, and seek there.
    133  *
    134  * @param io open I/O state
    135  * @param stream stream to seek in
    136  * @param ctx decoder to flush after seeking
    137  * @param offset desired position in seconds
    138  * @return the position we actually aim for, in seconds; 0 if we could
    139  *         not seek and the caller should just decode from the start
    140  */
    141 double
    142 EXTRACTOR_ffmpeg_seek_ (struct EXTRACTOR_FFmpegIO *io,
    143                         int stream,
    144                         AVCodecContext *ctx,
    145                         unsigned int offset);
    146 
    147 
    148 /**
    149  * Suppress FFmpeg's logging.
    150  */
    151 void
    152 EXTRACTOR_ffmpeg_silence_ (void);
    153 
    154 #endif
    155 
    156 /* end of mediaffmpeg.h */