播放器系列之ffplay源码分析（一）

最近在分析ffmpeg4.0中的播放器源码ffplay.c，这里将一些心得体会记录下来。
ffplay是一个独立文件，下面是入口函数：

int main(int argc, char **argv)
{
    int flags;
    VideoState *is;

    init_dynload();

    av_log_set_flags(AV_LOG_SKIP_REPEATED);
    parse_loglevel(argc, argv, options);

    /* register all codecs, demux and protocols */
#if CONFIG_AVDEVICE
    avdevice_register_all();
#endif
    avformat_network_init();

    init_opts();

    signal(SIGINT , sigterm_handler); /* Interrupt (ANSI).    */
    signal(SIGTERM, sigterm_handler); /* Termination (ANSI).  */

    show_banner(argc, argv, options);

    parse_options(NULL, argc, argv, options, opt_input_file);

    if (!input_filename) {
        show_usage();
        av_log(NULL, AV_LOG_FATAL, "An input file must be specified\n");
        av_log(NULL, AV_LOG_FATAL,
               "Use -h to get full help or, even better, run 'man %s'\n", program_name);
        exit(1);
    }

    if (display_disable) {
        video_disable = 1;
    }
    flags = SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER;
    if (audio_disable)
        flags &= ~SDL_INIT_AUDIO;
    else {
        /* Try to work around an occasional ALSA buffer underflow issue when the
         * period size is NPOT due to ALSA resampling by forcing the buffer size. */
        if (!SDL_getenv("SDL_AUDIO_ALSA_SET_BUFFER_SIZE"))
            SDL_setenv("SDL_AUDIO_ALSA_SET_BUFFER_SIZE","1", 1);
    }
    if (display_disable)
        flags &= ~SDL_INIT_VIDEO;
    if (SDL_Init (flags)) {
        av_log(NULL, AV_LOG_FATAL, "Could not initialize SDL - %s\n", SDL_GetError());
        av_log(NULL, AV_LOG_FATAL, "(Did you set the DISPLAY variable?)\n");
        exit(1);
    }

    SDL_EventState(SDL_SYSWMEVENT, SDL_IGNORE);
    SDL_EventState(SDL_USEREVENT, SDL_IGNORE);

    av_init_packet(&flush_pkt);
    flush_pkt.data = (uint8_t *)&flush_pkt;

    if (!display_disable) {
        int flags = SDL_WINDOW_HIDDEN;
        if (borderless)
            flags |= SDL_WINDOW_BORDERLESS;
        else
            flags |= SDL_WINDOW_RESIZABLE;
        window = SDL_CreateWindow(program_name, SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, default_width, default_height, flags);
        SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "linear");
        if (window) {
            renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
            if (!renderer) {
                av_log(NULL, AV_LOG_WARNING, "Failed to initialize a hardware accelerated renderer: %s\n", SDL_GetError());
                renderer = SDL_CreateRenderer(window, -1, 0);
            }
            if (renderer) {
                if (!SDL_GetRendererInfo(renderer, &renderer_info))
                    av_log(NULL, AV_LOG_VERBOSE, "Initialized %s renderer.\n", renderer_info.name);
            }
        }
        if (!window || !renderer || !renderer_info.num_texture_formats) {
            av_log(NULL, AV_LOG_FATAL, "Failed to create window or renderer: %s", SDL_GetError());
            do_exit(NULL);
        }
    }

    is = stream_open(input_filename, file_iformat);
    if (!is) {
        av_log(NULL, AV_LOG_FATAL, "Failed to initialize VideoState!\n");
        do_exit(NULL);
    }

    event_loop(is);

    /* never returns */

    return 0;
}