AVFilterGraph* filter_graph = avfilter_graph_alloc();
if (!filter_graph) {
    printf("Fail to create filter graph!\n");
    return -1;
}

// source filter
char args[512];
sprintf(args,
    "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
    in_width, in_height, AV_PIX_FMT_YUV420P,
    1, 25, 1, 1);
AVFilter* bufferSrc = avfilter_get_by_name("buffer");   // AVFilterGraph的输入源
AVFilterContext* bufferSrc_ctx;
ret = avfilter_graph_create_filter(&bufferSrc_ctx, bufferSrc, "in", args, NULL, filter_graph);
if (ret < 0) {
    printf("Fail to create filter bufferSrc\n");
    return -1;
}

// sink filter
AVBufferSinkParams *bufferSink_params;
AVFilterContext* bufferSink_ctx;
AVFilter* bufferSink = avfilter_get_by_name("buffersink");
enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE };
bufferSink_params = av_buffersink_params_alloc();
bufferSink_params->pixel_fmts = pix_fmts;
ret = avfilter_graph_create_filter(&bufferSink_ctx, bufferSink, "out", NULL,
                                    bufferSink_params, filter_graph);
if (ret < 0) {
    printf("Fail to create filter sink filter\n");
    return -1;
}

// split filter , 将视频分成两个流
AVFilter *splitFilter = avfilter_get_by_name("split");
AVFilterContext *splitFilter_ctx;
ret = avfilter_graph_create_filter(&splitFilter_ctx, splitFilter, "split", "outputs=2",
                                    NULL, filter_graph);
if (ret < 0) {
    printf("Fail to create split filter\n");
    return -1;
}

// crop filter ， 裁剪
AVFilter *cropFilter = avfilter_get_by_name("crop");
AVFilterContext *cropFilter_ctx;
ret = avfilter_graph_create_filter(&cropFilter_ctx, cropFilter, "crop",
                                    "out_w=iw:out_h=ih/2:x=0:y=0", NULL, filter_graph);
if (ret < 0) {
    printf("Fail to create crop filter\n");
    return -1;
}

// vflip filter ， 垂直翻转
AVFilter *vflipFilter = avfilter_get_by_name("vflip");
AVFilterContext *vflipFilter_ctx;
ret = avfilter_graph_create_filter(&vflipFilter_ctx, vflipFilter, "vflip", NULL, NULL, filter_graph);
if (ret < 0) {
    printf("Fail to create vflip filter\n");
    return -1;
}

// overlay filter ， 将多个流合成一个流
AVFilter *overlayFilter = avfilter_get_by_name("overlay");
AVFilterContext *overlayFilter_ctx;
ret = avfilter_graph_create_filter(&overlayFilter_ctx, overlayFilter, "overlay",
                                    "y=0:H/2", NULL, filter_graph);
if (ret < 0) {
    printf("Fail to create overlay filter\n");
    return -1;
}

// src filter to split filter ， 输入分出两个流
ret = avfilter_link(bufferSrc_ctx, 0, splitFilter_ctx, 0);
if (ret != 0) {
    printf("Fail to link src filter and split filter\n");
    return -1;
}
// split filter's first pad to overlay filter's main pad ， 一个流加入叠加过滤器
ret = avfilter_link(splitFilter_ctx, 0, overlayFilter_ctx, 0);
if (ret != 0) {
    printf("Fail to link split filter and overlay filter main pad\n");
    return -1;
}
// split filter's second pad to crop filter， 另一个流先进行裁剪
ret = avfilter_link(splitFilter_ctx, 1, cropFilter_ctx, 0);
if (ret != 0) {
    printf("Fail to link split filter's second pad and crop filter\n");
    return -1;
}
// crop filter to vflip filter ， 裁剪后的流加入垂直翻转过滤器中
ret = avfilter_link(cropFilter_ctx, 0, vflipFilter_ctx, 0);
if (ret != 0) {
    printf("Fail to link crop filter and vflip filter\n");
    return -1;
}
// vflip filter to overlay filter's second pad， 垂直翻转过滤器加入叠加过滤器中
ret = avfilter_link(vflipFilter_ctx, 0, overlayFilter_ctx, 1);
if (ret != 0) {
    printf("Fail to link vflip filter and overlay filter's second pad\n");
    return -1;
}
// overlay filter to sink filter， 叠加过滤器加入输出sink中
ret = avfilter_link(overlayFilter_ctx, 0, bufferSink_ctx, 0);
if (ret != 0) {
    printf("Fail to link overlay filter and sink filter\n");
    return -1;
}

// check filter graph
ret = avfilter_graph_config(filter_graph, NULL);
if (ret < 0) {
    printf("Fail in filter graph\n");
    return -1;
}

char *graph_str = avfilter_graph_dump(filter_graph, NULL);
FILE* graphFile = NULL;
fopen_s(&graphFile, "graphFile.txt", "w");  // 打印filtergraph的具体情况
fprintf(graphFile, "%s", graph_str);
av_free(graph_str);

if (av_buffersrc_add_frame(bufferSrc_ctx, frame_in) < 0) {
    printf("Error while add frame.\n");
    break;
}

// filter内部自己处理
/* pull filtered pictures from the filtergraph */
ret = av_buffersink_get_frame(bufferSink_ctx, frame_out);
if (ret < 0)
    break;

//output Y,U,V
if (frame_out->format == AV_PIX_FMT_YUV420P) {
    for (int i = 0; i < frame_out->height; i++) {
        fwrite(frame_out->data[0] + frame_out->linesize[0] * i, 1, frame_out->width, outFile);
    }
    for (int i = 0; i < frame_out->height / 2; i++) {
        fwrite(frame_out->data[1] + frame_out->linesize[1] * i, 1, frame_out->width / 2, outFile);
    }
    for (int i = 0; i < frame_out->height / 2; i++) {
        fwrite(frame_out->data[2] + frame_out->linesize[2] * i, 1, frame_out->width / 2, outFile);
    }
}

avfilter_graph_free(&filter_graph); // 内部去释放AVFilterContext产生的内存