avformat.h

rtsp协议的主要实现代码

/*
 * copyright (c) 2001 Fabrice Bellard
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#ifndef AVFORMAT_H
#define AVFORMAT_H

#ifdef __cplusplus
extern "C" {
#endif

#define LIBAVFORMAT_VERSION_INT ((51<<16)+(11<<8)+0)
#define LIBAVFORMAT_VERSION     51.11.0
#define LIBAVFORMAT_BUILD       LIBAVFORMAT_VERSION_INT

#define LIBAVFORMAT_IDENT       "Lavf" AV_STRINGIFY(LIBAVFORMAT_VERSION)

#include <time.h>
#include <stdio.h>  /* FILE */
#include "avcodec.h"

#include "avio.h"

/* packet functions */

typedef struct AVPacket {
    int64_t pts;                            ///< presentation time stamp in time_base units
    int64_t dts;                            ///< decompression time stamp in time_base units
    uint8_t *data;
    int   size;
    int   stream_index;
    int   flags;
    int   duration;                         ///< presentation duration in time_base units (0 if not available)
    void  (*destruct)(struct AVPacket *);
    void  *priv;
    int64_t pos;                            ///< byte position in stream, -1 if unknown
} AVPacket;
#define PKT_FLAG_KEY   0x0001

void av_destruct_packet_nofree(AVPacket *pkt);

/**
 * Default packet destructor.
 */
void av_destruct_packet(AVPacket *pkt);

/* initialize optional fields of a packet */
static inline void av_init_packet(AVPacket *pkt)
{
    pkt->pts   = AV_NOPTS_VALUE;
    pkt->dts   = AV_NOPTS_VALUE;
    pkt->pos   = -1;
    pkt->duration = 0;
    pkt->flags = 0;
    pkt->stream_index = 0;
    pkt->destruct= av_destruct_packet_nofree;
}

/**
 * Allocate the payload of a packet and intialized its fields to default values.
 *
 * @param pkt packet
 * @param size wanted payload size
 * @return 0 if OK. AVERROR_xxx otherwise.
 */
int av_new_packet(AVPacket *pkt, int size);

/**
 * Allocate and read the payload of a packet and intialized its fields to default values.
 *
 * @param pkt packet
 * @param size wanted payload size
 * @return >0 (read size) if OK. AVERROR_xxx otherwise.
 */
int av_get_packet(ByteIOContext *s, AVPacket *pkt, int size);

/**
 * @warning This is a hack - the packet memory allocation stuff is broken. The
 * packet is allocated if it was not really allocated
 */
int av_dup_packet(AVPacket *pkt);

/**
 * Free a packet
 *
 * @param pkt packet to free
 */
static inline void av_free_packet(AVPacket *pkt)
{
    if (pkt && pkt->destruct) {
        pkt->destruct(pkt);
    }
}

/*************************************************/
/* fractional numbers for exact pts handling */

/* the exact value of the fractional number is: 'val + num / den'. num
   is assumed to be such as 0 <= num < den */
typedef struct AVFrac {
    int64_t val, num, den;
} AVFrac attribute_deprecated;

/*************************************************/
/* input/output formats */

struct AVCodecTag;

struct AVFormatContext;

/** this structure contains the data a format has to probe a file */
typedef struct AVProbeData {
    const char *filename;
    unsigned char *buf;
    int buf_size;
} AVProbeData;

#define AVPROBE_SCORE_MAX 100               ///< max score, half of that is used for file extension based detection

typedef struct AVFormatParameters {
    AVRational time_base;
    int sample_rate;
    int channels;
    int width;
    int height;
    enum PixelFormat pix_fmt;
    int channel; /**< used to select dv channel */
#if LIBAVFORMAT_VERSION_INT < (52<<16)
    const char *device; /**< video, audio or DV device */
#endif
    const char *standard; /**< tv standard, NTSC, PAL, SECAM */
    int mpeg2ts_raw:1;  /**< force raw MPEG2 transport stream output, if possible */
    int mpeg2ts_compute_pcr:1; /**< compute exact PCR for each transport
                                  stream packet (only meaningful if
                                  mpeg2ts_raw is TRUE */
    int initial_pause:1;       /**< do not begin to play the stream
                                  immediately (RTSP only) */
    int prealloced_context:1;
    enum CodecID video_codec_id;
    enum CodecID audio_codec_id;
} AVFormatParameters;

//! demuxer will use url_fopen, no opened file should be provided by the caller
#define AVFMT_NOFILE        0x0001
#define AVFMT_NEEDNUMBER    0x0002 /**< needs '%d' in filename */
#define AVFMT_SHOW_IDS      0x0008 /**< show format stream IDs numbers */
#define AVFMT_RAWPICTURE    0x0020 /**< format wants AVPicture structure for
                                      raw picture data */
#define AVFMT_GLOBALHEADER  0x0040 /**< format wants global header */
#define AVFMT_NOTIMESTAMPS  0x0080 /**< format doesnt need / has any timestamps */
#define AVFMT_GENERIC_INDEX 0x0100 /**< use generic index building code */

typedef struct AVOutputFormat {
    const char *name;
    const char *long_name;
    const char *mime_type;
    const char *extensions; /**< comma separated filename extensions */
    /** size of private data so that it can be allocated in the wrapper */
    int priv_data_size;
    /* output support */
    enum CodecID audio_codec; /**< default audio codec */
    enum CodecID video_codec; /**< default video codec */
    int (*write_header)(struct AVFormatContext *);
    int (*write_packet)(struct AVFormatContext *, AVPacket *pkt);
    int (*write_trailer)(struct AVFormatContext *);
    /** can use flags: AVFMT_NOFILE, AVFMT_NEEDNUMBER, AVFMT_GLOBALHEADER */
    int flags;
    /** currently only used to set pixel format if not YUV420P */
    int (*set_parameters)(struct AVFormatContext *, AVFormatParameters *);
    int (*interleave_packet)(struct AVFormatContext *, AVPacket *out, AVPacket *in, int flush);

    /**
     * list of supported codec_id-codec_tag pairs, ordered by "better choice first"
     * the arrays are all CODEC_ID_NONE terminated
     */
    const struct AVCodecTag **codec_tag;

    /* private fields */
    struct AVOutputFormat *next;
} AVOutputFormat;

typedef struct AVInputFormat {
    const char *name;
    const char *long_name;
    /** size of private data so that it can be allocated in the wrapper */
    int priv_data_size;
    /** tell if a given file has a chance of being parsing by this format */
    int (*read_probe)(AVProbeData *);
    /** read the format header and initialize the AVFormatContext
       structure. Return 0 if OK. 'ap' if non NULL contains
       additionnal paramters. Only used in raw format right
       now. 'av_new_stream' should be called to create new streams.  */
    int (*read_header)(struct AVFormatContext *,
                       AVFormatParameters *ap);
    /** read one packet and put it in 'pkt'. pts and flags are also
       set. 'av_new_stream' can be called only if the flag
       AVFMTCTX_NOHEADER is used. */
    int (*read_packet)(struct AVFormatContext *, AVPacket *pkt);
    /** close the stream. The AVFormatContext and AVStreams are not
       freed by this function */
    int (*read_close)(struct AVFormatContext *);
    /**
     * seek to a given timestamp relative to the frames in
     * stream component stream_index
     * @param stream_index must not be -1
     * @param flags selects which direction should be preferred if no exact
     *              match is available
     */
    int (*read_seek)(struct AVFormatContext *,
                     int stream_index, int64_t timestamp, int flags);
    /**
     * gets the next timestamp in AV_TIME_BASE units.
     */
    int64_t (*read_timestamp)(struct AVFormatContext *s, int stream_index,
                              int64_t *pos, int64_t pos_limit);
    /** can use flags: AVFMT_NOFILE, AVFMT_NEEDNUMBER */
    int flags;
    /** if extensions are defined, then no probe is done. You should
       usually not use extension format guessing because it is not
       reliable enough */
    const char *extensions;
    /** general purpose read only value that the format can use */
    int value;

    /** start/resume playing - only meaningful if using a network based format
       (RTSP) */
    int (*read_play)(struct AVFormatContext *);

    /** pause playing - only meaningful if using a network based format
       (RTSP) */
    int (*read_pause)(struct AVFormatContext *);

    const struct AVCodecTag **codec_tag;

    /* private fields */
    struct AVInputFormat *next;
} AVInputFormat;

typedef struct AVIndexEntry {
    int64_t pos;
    int64_t timestamp;
#define AVINDEX_KEYFRAME 0x0001
    int flags:2;
    int size:30; //yeah trying to keep the size of this small to reduce memory requirements (its 24 vs 32 byte due to possible 8byte align)
    int min_distance;         /**< min distance between this and the previous keyframe, used to avoid unneeded searching */
} AVIndexEntry;

typedef struct AVStream {
    int index;    /**< stream index in AVFormatContext */
    int id;       /**< format specific stream id */
    AVCodecContext *codec; /**< codec context */
    /**
     * real base frame rate of the stream.
     * this is the lowest framerate with which all timestamps can be
     * represented accurately (its the least common multiple of all
     * framerates in the stream), Note, this value is just a guess!
     * for example if the timebase is 1/90000 and all frames have either
     * approximately 3600 or 1800 timer ticks then r_frame_rate will be 50/1
     */
    AVRational r_frame_rate;
    void *priv_data;
#if LIBAVFORMAT_VERSION_INT < (52<<16)
    /* internal data used in av_find_stream_info() */
    int64_t codec_info_duration;
    int codec_info_nb_frames;
#endif
    /** encoding: PTS generation when outputing stream */
    AVFrac pts;

    /**
     * this is the fundamental unit of time (in seconds) in terms
     * of which frame timestamps are represented. for fixed-fps content,
     * timebase should be 1/framerate and timestamp increments should be
     * identically 1.
     */
    AVRational time_base;
    int pts_wrap_bits; /**< number of bits in pts (used for wrapping control) */
    /* ffmpeg.c private use */
    int stream_copy; /**< if set, just copy stream */
    enum AVDiscard discard; ///< selects which packets can be discarded at will and dont need to be demuxed