int avfilter_graph_add_filter(AVFilterGraph *graph, AVFilterContext *filter)
{
    AVFilterContext **filters = av_realloc(graph->filters,
                                           sizeof(AVFilterContext*) * (graph->filter_count+1));
    if (!filters)
        return AVERROR(ENOMEM);

    graph->filters = filters;
    graph->filters[graph->filter_count++] = filter;

    return 0;
}