ffmpeg.c函数结构简单分析（画图）

标签：ffmpeg   函数   分析   

先说明一下自己画的结构图的规则：图中仅画出了比较重要的函数之间的调用关系。粉红色的函数是FFmpeg编解码类库（libavcodec，libavformat等）的API。绿色的函数是FFmpeg的libavfilter的API。其他不算很重要的函数就不再列出了。

PS：有一部分代码可能和ffmpeg.c有一些出入。因为本文使用的ffmpeg.c的代码是移植到VC之后的代码。

100行代码实现最简单的基于FFMPEG+SDL的视频播放器

最简单的基于FFmpeg+SDL的音频播放器

最简单的基于FFMPEG的视频编码器（YUV编码为H.264）

最简单的基于FFMPEG的音频编码器（PCM编码为AAC）

最简单的基于FFmpeg的转码程序

函数调用结构图

上图所示本是一张高清大图。但是页面显示不下。因此上传了一份：

http://my.csdn.net/leixiaohua1020/album/detail/1788075

上面地址的那张图保存下来的话就是一张清晰的图片了。

下文将会对主要函数分别解析。

main()

parse_options()

注：定义位于cmdutils.c中。

typedef struct OptionDef {
    const char *name;
    int flags;
#define HAS_ARG    0x0001
#define OPT_BOOL   0x0002
#define OPT_EXPERT 0x0004
#define OPT_STRING 0x0008
#define OPT_VIDEO  0x0010
#define OPT_AUDIO  0x0020
#define OPT_INT    0x0080
#define OPT_FLOAT  0x0100
#define OPT_SUBTITLE 0x0200
#define OPT_INT64  0x0400
#define OPT_EXIT   0x0800
#define OPT_DATA   0x1000
#define OPT_PERFILE  0x2000     /* the option is per-file (currently ffmpeg-only).
         implied by OPT_OFFSET or OPT_SPEC */
#define OPT_OFFSET 0x4000       /* option is specified as an offset in a passed optctx */
#define OPT_SPEC   0x8000       /* option is to be stored in an array of SpecifierOpt.
         Implies OPT_OFFSET. Next element after the offset is
         an int containing element count in the array. */
#define OPT_TIME  0x10000
#define OPT_DOUBLE 0x20000
     union {
        void *dst_ptr;
        int (*func_arg)(void *, const char *, const char *);
        size_t off;
    } u;
    const char *help;
    const char *argname;
} OptionDef;

    { "L"          , OPT_EXIT, {(void*)show_license},      "show license" },
    { "h"          , OPT_EXIT, {(void*) show_help},         "show help", "topic" },
    { "?"          , OPT_EXIT, {(void*)show_help},         "show help", "topic" },
    { "help"       , OPT_EXIT, {(void*)show_help},         "show help", "topic" },
    { "-help"      , OPT_EXIT, {(void*)show_help},         "show help", "topic" },
    { "version"    , OPT_EXIT, {(void*)show_version},      "show version" },
    { "formats"    , OPT_EXIT, {(void*)show_formats  },    "show available formats" },
    { "codecs"     , OPT_EXIT, {(void*)show_codecs   },    "show available codecs" },
    { "decoders"   , OPT_EXIT, {(void*)show_decoders },    "show available decoders" },
    { "encoders"   , OPT_EXIT, {(void*)show_encoders },    "show available encoders" },
    { "bsfs"       , OPT_EXIT, {(void*)show_bsfs     },    "show available bit stream filters" },
    { "protocols"  , OPT_EXIT, {(void*)show_protocols},    "show available protocols" },
    { "filters"    , OPT_EXIT, {(void*)show_filters  },    "show available filters" },
    { "pix_fmts"   , OPT_EXIT, {(void*)show_pix_fmts },    "show available pixel formats" },
    { "layouts"    , OPT_EXIT, {(void*)show_layouts  },    "show standard channel layouts" },
    { "sample_fmts", OPT_EXIT, {(void*)show_sample_fmts }, "show available audio sample formats" },
    { "loglevel"   , HAS_ARG,  {(void*)opt_loglevel},      "set libav* logging level", "loglevel" },
    { "v",           HAS_ARG,  {(void*)opt_loglevel},      "set libav* logging level", "loglevel" },
    { "debug"      , HAS_ARG,  {(void*)opt_codec_debug},   "set debug flags", "flags" },
    { "fdebug"     , HAS_ARG,  {(void*)opt_codec_debug},   "set debug flags", "flags" },
    { "report"     , 0,        {(void*)opt_report}, "generate a report" },
    { "max_alloc"  , HAS_ARG,  {(void*) opt_max_alloc},     "set maximum size of a single allocated block", "bytes" },
    { "cpuflags"   , HAS_ARG | OPT_EXPERT, {(void*) opt_cpuflags}, "force specific cpu flags", "flags" },

const OptionDef options[] = {
    /* main options */
#include "cmdutils_common_opts.h"//包含了cmdutils_common_opts.h中的选项
    { "f", HAS_ARG | OPT_STRING | OPT_OFFSET,           { (void*)OFFSET(format) },
        "force format", "fmt" },
    { "i", HAS_ARG | OPT_PERFILE,          { (void*) opt_input_file },
        "input file name", "filename" },
    { "y", OPT_BOOL,          { &file_overwrite },
        "overwrite output files" },
    { "n", OPT_BOOL,          { &no_file_overwrite },
        "do not overwrite output files" },
    { "c", HAS_ARG | OPT_STRING | OPT_SPEC,{ (void*) OFFSET(codec_names) },
        "codec name", "codec" },
    { "codec",          HAS_ARG | OPT_STRING | OPT_SPEC,{(void*) OFFSET(codec_names) },
        "codec name", "codec" },
    { "pre",            HAS_ARG | OPT_STRING | OPT_SPEC,{ (void*) OFFSET(presets) },
        "preset name", "preset" },
    { "map",            HAS_ARG | OPT_EXPERT | OPT_PERFILE,          { (void*) opt_map },
        "set input stream mapping",
        "[-]input_file_id[:stream_specifier][,sync_file_id[:stream_specifier]]" },
    { "map_channel",    HAS_ARG | OPT_EXPERT | OPT_PERFILE,          {(void*)opt_map_channel },
        "map an audio channel from one stream to another", "file.stream.channel[:syncfile.syncstream]" },
    { "map_metadata",   HAS_ARG | OPT_STRING | OPT_SPEC,{ (void*)OFFSET(metadata_map) },
        "set metadata information of outfile from infile",
        "outfile[,metadata]:infile[,metadata]" },
    { "map_chapters",   HAS_ARG | OPT_INT | OPT_EXPERT | OPT_OFFSET, { (void*) OFFSET(chapters_input_file) },
        "set chapters mapping", "input_file_index" },
    { "t", HAS_ARG | OPT_TIME | OPT_OFFSET,{(void*) OFFSET(recording_time) },
        "record or transcode \"duration\" seconds of audio/video",
        "duration" },
    { "fs",HAS_ARG | OPT_INT64 | OPT_OFFSET,            { (void*) OFFSET(limit_filesize) },
        "set the limit file size in bytes", "limit_size" },
    { "ss",HAS_ARG | OPT_TIME | OPT_OFFSET,{ (void*) OFFSET(start_time) },
        "set the start time offset", "time_off" },
   …//选项太多，不一一列出
};

{ "i",HAS_ARG | OPT_PERFILE, { (void*) opt_input_file }, "input file name", "filename" }

static int opt_input_file(void *optctx, const char *opt, const char *filename)
{
    //略…
    /* open the input file with generic avformat function */
    err = avformat_open_input(&ic, filename, file_iformat, &format_opts);
    if (err < 0) {
        print_error(filename, err);
        exit(1);
    }
   
    //略…
    /* Set AVCodecContext options for avformat_find_stream_info */
    opts = setup_find_stream_info_opts(ic, codec_opts);
    orig_nb_streams = ic->nb_streams;
 
    /* If not enough info to get the stream parameters, we decode the
       first frames to get it. (used in mpeg case for example) */
    ret = avformat_find_stream_info(ic, opts);
    if (ret < 0) {
        av_log(NULL, AV_LOG_FATAL, "%s: could not find codec parameters\n", filename);
        avformat_close_input(&ic);
        exit(1);
    }
   
    //略…
    /* dump the file content */
    av_dump_format(ic, nb_input_files, filename, 0);
   
    //略…
    return 0;
}

ffmpeg -i xxx.mpg xxx.mkv

ffmpeg -i xxx.mpeg -o xxx.mkv

void opt_output_file(void *optctx, const char *filename)
{
    //略…
    err = avformat_alloc_output_context2(&oc, NULL, o->format, filename);
 
    if (!oc) {
        print_error(filename, err);
        exit(1);
    }
    //略…
   new_video_stream();
   …
   new_audio_stream();
   …
   new_subtitle_stream ();
    //略…
 
}
 

transcode()

下图红框所示即为print_report()打印输出到屏幕上的信息。

transcode_init()

transcode_step()

process_input()

configure_filtergraph()

未分析。

reap_filters()

exit_program()

附录

FFmpeg转码时在屏幕上的输出。

//输入信息（main()->parse_options()->opt_input_file()->av_dump_format()）

//输出信息（main()->transcode()->transcode_init()->av_dump_format()）

//输出Stream Maping 信息（main()->transcode()->transcode_init()）

//一行字（main()->transcode()）

//输出信息（main()->transcode()->print_report()）

//最后一次输出

//avcodec_close()的时候输出（libx264专有的输出信息）

ffmpeg.c函数结构简单分析（画图）

标签：ffmpeg   函数   分析   

原文地址：http://blog.csdn.net/leixiaohua1020/article/details/39760711