static int check_format_change_video(AVFilterContext *buffer_filter,
                                     AVFilterBufferRef *picref)
{
    BufferSourceContext *c = buffer_filter->priv;
    int ret;

    if (picref->video->w != c->w || picref->video->h != c->h || picref->format != c->pix_fmt) {
        AVFilterContext *scale = buffer_filter->outputs[0]->dst;
        AVFilterLink *link;
        char scale_param[1024];

        av_log(buffer_filter, AV_LOG_INFO,
               "Buffer video input changed from size:%dx%d fmt:%s to size:%dx%d fmt:%s\n",
               c->w, c->h, av_pix_fmt_descriptors[c->pix_fmt].name,
               picref->video->w, picref->video->h, av_pix_fmt_descriptors[picref->format].name);

        if (!scale || strcmp(scale->filter->name, "scale")) {
            AVFilter *f = avfilter_get_by_name("scale");

            av_log(buffer_filter, AV_LOG_INFO, "Inserting scaler filter\n");
            if ((ret = avfilter_open(&scale, f, "Input equalizer")) < 0)
                return ret;

            c->scale = scale;

            snprintf(scale_param, sizeof(scale_param)-1, "%d:%d:%s", c->w, c->h, c->sws_param);
            if ((ret = avfilter_init_filter(scale, scale_param, NULL)) < 0) {
                return ret;
            }

            if ((ret = avfilter_insert_filter(buffer_filter->outputs[0], scale, 0, 0)) < 0) {
                return ret;
            }
            scale->outputs[0]->time_base = scale->inputs[0]->time_base;

            scale->outputs[0]->format= c->pix_fmt;
        } else if (!strcmp(scale->filter->name, "scale")) {
            snprintf(scale_param, sizeof(scale_param)-1, "%d:%d:%s",
                     scale->outputs[0]->w, scale->outputs[0]->h, c->sws_param);
            scale->filter->init(scale, scale_param, NULL);
        }

        c->pix_fmt = scale->inputs[0]->format = picref->format;
        c->w       = scale->inputs[0]->w      = picref->video->w;
        c->h       = scale->inputs[0]->h      = picref->video->h;

        link = scale->outputs[0];
        if ((ret =  link->srcpad->config_props(link)) < 0)
            return ret;
    }
    return 0;
}