ffplay源码分析06 ---- 视频输出

 =====================================================

ffplay源码分析01 ---- 框架

ffplay源码分析02 ---- 数据读取线程

ffplay源码分析03 ---- 视频解码线程

ffplay源码分析03 ---- 音频解码线程

ffplay源码分析04 ---- 音频输出

ffplay源码分析05 ---- 音频重采样

ffplay源码分析06 ---- 视频输出

ffplay源码分析07 ---- 音视频同步

=====================================================

初始化

/* Called from the main */
int main(int argc, char **argv)
{
    int flags;
    VideoState *is;
    //    av_log_set_level(AV_LOG_TRACE);
    init_dynload();
    // 1. 对FFmpeg的初始化
    av_log_set_flags(AV_LOG_SKIP_REPEATED);
    parse_loglevel(argc, argv, options);
    /// av_log_set_level(AV_LOG_DEBUG);
    /* 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);
    // 2. 对传递的参数进行初始化
    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
");
        av_log(NULL, AV_LOG_FATAL,
               "Use -h to get full help or, even better, run 'man %s'
", program_name);
        exit(1);
    }

    /* 是否显示视频 */
    if (display_disable) {
        video_disable = 1;
    }
    // 3. SDL的初始化
    flags = SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER;
    /* 是否运行音频 */
    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
", SDL_GetError());
        av_log(NULL, AV_LOG_FATAL, "(Did you set the DISPLAY variable?)
");
        exit(1);
    }

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

    av_init_packet(&flush_pkt);                // 初始化flush_packet
    flush_pkt.data = (uint8_t *)&flush_pkt; // 初始化为数据指向自己本身

    // 4. 创建窗口
    if (!display_disable) {
        int flags = SDL_WINDOW_HIDDEN;
        if (alwaysontop)
#if SDL_VERSION_ATLEAST(2,0,5)
            flags |= SDL_WINDOW_ALWAYS_ON_TOP;
#else
            av_log(NULL, AV_LOG_WARNING, "Your SDL version doesn't support SDL_WINDOW_ALWAYS_ON_TOP. Feature will be inactive.
");
#endif
        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) {
            // 创建renderer
            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
", 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.
", 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);
        }
    }
    // 5. 通过stream_open函数，开启read_thread读取线程
    is = stream_open(input_filename, file_iformat);
    if (!is) {
        av_log(NULL, AV_LOG_FATAL, "Failed to initialize VideoState!
");
        do_exit(NULL);
    }

    // 6. 事件响应
    event_loop(is);

    /* never returns */

    return 0;
}

初始化主要在main里面，主要做了如下几件事：

1. SDL_Init，主要是SDL_INIT_VIDEO的⽀持
2. SDL_CreateWindow，创建主窗⼝
3. SDL_CreateRender，基于主窗⼝创建renderer，⽤于渲染输出。
4. stream_open
5. event_loop，播放控制事件响应循环，但也负责了video显示输出。

video_refresh()

/* called to display each frame */
/* 非暂停或强制刷新的时候，循环调用video_refresh */
static void video_refresh(void *opaque, double *remaining_time)
{
    VideoState *is = opaque;
    double time;

    Frame *sp, *sp2;

    if (!is->paused && get_master_sync_type(is) == AV_SYNC_EXTERNAL_CLOCK && is->realtime)
        check_external_clock_speed(is);

    if (!display_disable && is->show_mode != SHOW_MODE_VIDEO && is->audio_st) {
        time = av_gettime_relative() / 1000000.0;
        if (is->force_refresh || is->last_vis_time + rdftspeed < time) {
            video_display(is);
            is->last_vis_time = time;
        }
        *remaining_time = FFMIN(*remaining_time, is->last_vis_time + rdftspeed - time);
    }

    if (is->video_st) {
retry:
        if (frame_queue_nb_remaining(&is->pictq) == 0) {// 帧队列是否为空
            // nothing to do, no picture to display in the queue
            // 什么都不做，队列中没有图像可显示
        } else { // 重点是音视频同步
            double last_duration, duration, delay;
            Frame *vp, *lastvp;

            /* dequeue the picture */
            // 从队列取出上一个Frame
            lastvp = frame_queue_peek_last(&is->pictq);//读取上一帧
            vp = frame_queue_peek(&is->pictq);  // 读取待显示帧
            // lastvp 上一帧(正在显示的帧)
            // vp 等待显示的帧

            if (vp->serial != is->videoq.serial) {
                // 如果不是最新的播放序列，则将其出队列，以尽快读取最新序列的帧
                frame_queue_next(&is->pictq);
                goto retry;
            }

            if (lastvp->serial != vp->serial) {
                // 新的播放序列重置当前时间
                is->frame_timer = av_gettime_relative() / 1000000.0;
            }

            if (is->paused)
            {
                goto display;
                printf("视频暂停is->paused");
            }
            /* compute nominal last_duration */
            //lastvp上一帧，vp当前帧 ，nextvp下一帧
            //last_duration 计算上一帧应显示的时长
            last_duration = vp_duration(is, lastvp, vp);

            // 经过compute_target_delay方法，计算出待显示帧vp需要等待的时间
            // 如果以video同步，则delay直接等于last_duration。
            // 如果以audio或外部时钟同步，则需要比对主时钟调整待显示帧vp要等待的时间。
            delay = compute_target_delay(last_duration, is);

            time= av_gettime_relative()/1000000.0;
            // is->frame_timer 实际上就是上一帧lastvp的播放时间,
            // is->frame_timer + delay 是待显示帧vp该播放的时间
            if (time < is->frame_timer + delay) { //判断是否继续显示上一帧
                // 当前系统时刻还未到达上一帧的结束时刻，那么还应该继续显示上一帧。
                // 计算出最小等待时间
                *remaining_time = FFMIN(is->frame_timer + delay - time, *remaining_time);
                goto display;
            }

            // 走到这一步，说明已经到了或过了该显示的时间，待显示帧vp的状态变更为当前要显示的帧

            is->frame_timer += delay;   // 更新当前帧播放的时间
            if (delay > 0 && time - is->frame_timer > AV_SYNC_THRESHOLD_MAX) {
                is->frame_timer = time; //如果和系统时间差距太大，就纠正为系统时间
            }
            SDL_LockMutex(is->pictq.mutex);
            if (!isnan(vp->pts))
                update_video_pts(is, vp->pts, vp->pos, vp->serial); // 更新video时钟
            SDL_UnlockMutex(is->pictq.mutex);
            //丢帧逻辑
            if (frame_queue_nb_remaining(&is->pictq) > 1) {//有nextvp才会检测是否该丢帧
                Frame *nextvp = frame_queue_peek_next(&is->pictq);
                duration = vp_duration(is, vp, nextvp);
                if(!is->step        // 非逐帧模式才检测是否需要丢帧 is->step==1 为逐帧播放
                        && (framedrop>0 ||      // cpu解帧过慢
                            (framedrop && get_master_sync_type(is) != AV_SYNC_VIDEO_MASTER)) // 非视频同步方式
                        && time > is->frame_timer + duration // 确实落后了一帧数据
                        ) {
                    printf("%s(%d) dif:%lfs, drop frame
", __FUNCTION__, __LINE__,
                           (is->frame_timer + duration) - time);
                    is->frame_drops_late++;             // 统计丢帧情况
                    frame_queue_next(&is->pictq);       // 这里实现真正的丢帧
                    //(这里不能直接while丢帧，因为很可能audio clock重新对时了，这样delay值需要重新计算)
                    goto retry; //回到函数开始位置，继续重试
                }
            }

            if (is->subtitle_st) {
                while (frame_queue_nb_remaining(&is->subpq) > 0) {
                    sp = frame_queue_peek(&is->subpq);

                    if (frame_queue_nb_remaining(&is->subpq) > 1)
                        sp2 = frame_queue_peek_next(&is->subpq);
                    else
                        sp2 = NULL;

                    if (sp->serial != is->subtitleq.serial
                            || (is->vidclk.pts > (sp->pts + ((float) sp->sub.end_display_time / 1000)))
                            || (sp2 && is->vidclk.pts > (sp2->pts + ((float) sp2->sub.start_display_time / 1000))))
                    {
                        if (sp->uploaded) {
                            int i;
                            for (i = 0; i < sp->sub.num_rects; i++) {
                                AVSubtitleRect *sub_rect = sp->sub.rects[i];
                                uint8_t *pixels;
                                int pitch, j;

                                if (!SDL_LockTexture(is->sub_texture, (SDL_Rect *)sub_rect, (void **)&pixels, &pitch)) {
                                    for (j = 0; j < sub_rect->h; j++, pixels += pitch)
                                        memset(pixels, 0, sub_rect->w << 2);
                                    SDL_UnlockTexture(is->sub_texture);
                                }
                            }
                        }
                        frame_queue_next(&is->subpq);
                    } else {
                        break;
                    }
                }
            }

            frame_queue_next(&is->pictq);   // 当前vp帧出队列
            is->force_refresh = 1;          /* 说明需要刷新视频帧 */

            if (is->step && !is->paused)
                stream_toggle_pause(is);
        }
display:
        /* display picture */
        if (!display_disable && is->force_refresh && is->show_mode == SHOW_MODE_VIDEO && is->pictq.rindex_shown)
            video_display(is); // 重点是显示
    }
    is->force_refresh = 0;
    if (show_status) {
        static int64_t last_time;
        int64_t cur_time;
        int aqsize, vqsize, sqsize;
        double av_diff;

        cur_time = av_gettime_relative();
        if (!last_time || (cur_time - last_time) >= 30000) {
            aqsize = 0;
            vqsize = 0;
            sqsize = 0;
            if (is->audio_st)
                aqsize = is->audioq.size;
            if (is->video_st)
                vqsize = is->videoq.size;
            if (is->subtitle_st)
                sqsize = is->subtitleq.size;
            av_diff = 0;
            if (is->audio_st && is->video_st)
                av_diff = get_clock(&is->audclk) - get_clock(&is->vidclk);
            else if (is->video_st)
                av_diff = get_master_clock(is) - get_clock(&is->vidclk);
            else if (is->audio_st)
                av_diff = get_master_clock(is) - get_clock(&is->audclk);
            av_log(NULL, AV_LOG_INFO,
                   "%7.2f %s:%7.3f fd=%4d aq=%5dKB vq=%5dKB sq=%5dB f=%"PRId64"/%"PRId64"   
",
                   get_master_clock(is),
                   (is->audio_st && is->video_st) ? "A-V" : (is->video_st ? "M-V" : (is->audio_st ? "M-A" : "   ")),
                   av_diff,
                   is->frame_drops_early + is->frame_drops_late,
                   aqsize / 1024,
                   vqsize / 1024,
                   sqsize,
                   is->video_st ? is->viddec.avctx->pts_correction_num_faulty_dts : 0,
                   is->video_st ? is->viddec.avctx->pts_correction_num_faulty_pts : 0);
            fflush(stdout);
            last_time = cur_time;
        }
    }
}

 video_image_display()

static void video_image_display(VideoState *is)
{
    Frame *vp;
    Frame *sp = NULL;
    SDL_Rect rect;

    // keep_last的作用就出来了,我们是有调用frame_queue_next, 但最近出队列的帧并没有真正销毁
    // 所以这里可以读取出来显示
    vp = frame_queue_peek_last(&is->pictq);
    if (is->subtitle_st) {
        if (frame_queue_nb_remaining(&is->subpq) > 0) {
            sp = frame_queue_peek(&is->subpq);

            if (vp->pts >= sp->pts + ((float) sp->sub.start_display_time / 1000)) {
                if (!sp->uploaded) {
                    uint8_t* pixels[4];
                    int pitch[4];
                    int i;
                    if (!sp->width || !sp->height) {
                        sp->width = vp->width;
                        sp->height = vp->height;
                    }
                    if (realloc_texture(&is->sub_texture, SDL_PIXELFORMAT_ARGB8888, sp->width, sp->height, SDL_BLENDMODE_BLEND, 1) < 0)
                        return;

                    for (i = 0; i < sp->sub.num_rects; i++) {
                        AVSubtitleRect *sub_rect = sp->sub.rects[i];

                        sub_rect->x = av_clip(sub_rect->x, 0, sp->width );
                        sub_rect->y = av_clip(sub_rect->y, 0, sp->height);
                        sub_rect->w = av_clip(sub_rect->w, 0, sp->width  - sub_rect->x);
                        sub_rect->h = av_clip(sub_rect->h, 0, sp->height - sub_rect->y);

                        is->sub_convert_ctx = sws_getCachedContext(is->sub_convert_ctx,
                                                                   sub_rect->w, sub_rect->h, AV_PIX_FMT_PAL8,
                                                                   sub_rect->w, sub_rect->h, AV_PIX_FMT_BGRA,
                                                                   0, NULL, NULL, NULL);
                        if (!is->sub_convert_ctx) {
                            av_log(NULL, AV_LOG_FATAL, "Cannot initialize the conversion context
");
                            return;
                        }
                        if (!SDL_LockTexture(is->sub_texture, (SDL_Rect *)sub_rect, (void **)pixels, pitch)) {
                            sws_scale(is->sub_convert_ctx, (const uint8_t * const *)sub_rect->data, sub_rect->linesize,
                                      0, sub_rect->h, pixels, pitch);
                            SDL_UnlockTexture(is->sub_texture);
                        }
                    }
                    sp->uploaded = 1;
                }
            } else
                sp = NULL;
        }
    }
    //将帧宽高按照sar最大适配到窗口，并通过rect返回视频帧在窗口的显示位置和宽高
    calculate_display_rect(&rect, is->xleft, is->ytop, is->width, is->height,
                           vp->width, vp->height, vp->sar);
//    rect.x = rect.w /2;   // 测试
//    rect.w = rect.w /2;   // 缩放实际不是用sws， 缩放是sdl去做的
    if (!vp->uploaded) {
        // 把yuv数据更新到vid_texture
        if (upload_texture(&is->vid_texture, vp->frame, &is->img_convert_ctx) < 0)
            return;
        vp->uploaded = 1;
        vp->flip_v = vp->frame->linesize[0] < 0;
    }

    set_sdl_yuv_conversion_mode(vp->frame);
    SDL_RenderCopyEx(renderer, is->vid_texture, NULL, &rect, 0, NULL, vp->flip_v ? SDL_FLIP_VERTICAL : 0);
    set_sdl_yuv_conversion_mode(NULL);
    if (sp) {
#if USE_ONEPASS_SUBTITLE_RENDER
        SDL_RenderCopy(renderer, is->sub_texture, NULL, &rect);
#else
        int i;
        double xratio = (double)rect.w / (double)sp->width;
        double yratio = (double)rect.h / (double)sp->height;
        for (i = 0; i < sp->sub.num_rects; i++) {
            SDL_Rect *sub_rect = (SDL_Rect*)sp->sub.rects[i];
            SDL_Rect target = {.x = rect.x + sub_rect->x * xratio,
                               .y = rect.y + sub_rect->y * yratio,
                               .w = sub_rect->w * xratio,
                               .h = sub_rect->h * yratio};
            SDL_RenderCopy(renderer, is->sub_texture, sub_rect, &target);
        }
#endif
    }
}