After generate AVFilterContext *,how can i change parameters?
Such as "drawbox=x=%d:y=%d:width=%d:height=%d:color=%s",
I used av_opt_set(filter_ctx->priv, "x", std::to_string(x).c_str(), 0);
But it didn t take effect.
What should i do for move the rect?

https://github.com/zhuziaho/drawRectOnFrame

int FilterUtils::initFilter(AVCodecContext *codecContext, const char *filter_str)
{
    // closeFilter();
    int ret = -1;
    char args[512];
    filter_graph = avfilter_graph_alloc();
    if (!filter_graph)
    {
        ret = AVERROR(ENOMEM);
        return -1;
    }
    buffersrc = avfilter_get_by_name("buffer");
    buffersink = avfilter_get_by_name("buffersink");
    sprintf(args,
            "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
            codecContext->width, codecContext->height, codecContext->pix_fmt,
            codecContext->time_base.num, codecContext->time_base.den,
            codecContext->sample_aspect_ratio.num, codecContext->sample_aspect_ratio.den);
    printf("%s
", args);
    ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
                                       args, NULL, filter_graph);
    if (ret < 0)
    {
        return -1;
    }

    ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
                                       NULL, NULL, filter_graph);

    if (ret < 0)
    {
        av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink
");
        return -1;
    }

    ret = av_opt_set_int_list(buffersink_ctx, "pix_fmts", pix_fmts,
                              AV_PIX_FMT_YUV420P, AV_OPT_SEARCH_CHILDREN);
    if (ret < 0)
    {
        av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format
");
        return -1;
    }

    outputs = avfilter_inout_alloc();
    inputs = avfilter_inout_alloc();
    if (!outputs || !inputs)
    {
        ret = AVERROR(ENOMEM);
        return -1;
    }
    outputs->name = av_strdup("in");
    outputs->filter_ctx = buffersrc_ctx;
    outputs->pad_idx = 0;
    outputs->next = NULL;

    inputs->name = av_strdup("out");
    inputs->filter_ctx = buffersink_ctx;
    inputs->pad_idx = 0;
    inputs->next = NULL;

    if ((ret = avfilter_graph_parse_ptr(filter_graph, "drawbox=x=100:y=100:width=50:height=50:color=#FFFFFF",
                                        &inputs, &outputs, NULL)) < 0)
        return -1;

    if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
        return -1;

    for (int i = 0; i < filter_graph->nb_filters; i++)
    {
        AVFilterContext *filter_ctxn = filter_graph->filters[i];
        fprintf(stdout, "[%s](%d) filter_ctxn->name=%s
", __func__, __LINE__, filter_ctxn->name);
    }
    filter_ctx = avfilter_graph_get_filter(filter_graph, "Parsed_drawbox_0");

    ret = 1;

    avfilter_inout_free(&inputs);
    avfilter_inout_free(&outputs);
    return ret;
};

AVFrame *FilterUtils::setFrame(AVFrame *inFrame)
{
    int ret = -1;
    AVFrame *pFrame = av_frame_alloc();

    // I want to move the drawbox by modifying the Filter parameter here
    av_opt_set(filter_ctx->priv, "x", std::to_string(500).c_str(), 0);

    ret = av_buffersrc_add_frame_flags(buffersrc_ctx, inFrame, AV_BUFFERSRC_FLAG_KEEP_REF);
    if (ret < 0)
    {
        return NULL;
    }
    ret = av_buffersink_get_frame_flags(buffersink_ctx, pFrame, 0);
    if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
    {
        return NULL;
    }
    return pFrame;
}