[FFmpeg-devel] [PATCH 2/3] avfiltergraph: don't query formats if filter has uninitialized inputs

[Nicolas George]

Le quintidi 15 floréal, an CCXX, Matthieu Bouron a écrit :
> ---
>  libavfilter/avfiltergraph.c |   46 ++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 39 insertions(+), 7 deletions(-)

Can you explain why this is necessary? I have some ideas, but I would like
to compare ideas.

> diff --git a/libavfilter/avfiltergraph.c b/libavfilter/avfiltergraph.c
> index 9d7b956..064e678 100644
> --- a/libavfilter/avfiltergraph.c
> +++ b/libavfilter/avfiltergraph.c
> @@ -202,17 +202,49 @@ static int insert_conv_filter(AVFilterGraph *graph, AVFilterLink *link,
>  
>  static int query_formats(AVFilterGraph *graph, AVClass *log_ctx)
>  {
> -    int i, j, ret;
> +    int i, j, k, ret;
>      char filt_args[128];
>      AVFilterFormats *formats, *chlayouts, *packing;
> +    int filters_init;
> +    int *filters_state = av_calloc(graph->filter_count, sizeof(int));
>  
>      /* ask all the sub-filters for their supported media formats */
> -    for (i = 0; i < graph->filter_count; i++) {
> -        if (graph->filters[i]->filter->query_formats)
> -            graph->filters[i]->filter->query_formats(graph->filters[i]);
> -        else
> -            avfilter_default_query_formats(graph->filters[i]);
> -    }
> +    do {
> +        filters_init = 1;
> +        for (i = 0; i < graph->filter_count; i++) {
> +            int do_query = 1;
> +            AVFilterContext *cur = graph->filters[i];
> +
> +            if (filters_state[i])
> +                continue;
> +
> +            /* Check state of input links */
> +            for (j = 0; j < cur->input_count; j++) {
> +                AVFilterContext *ifilter = cur->inputs[j]->src;
> +
> +                for(k = 0; k < graph->filter_count; k++) {
> +                    if (ifilter == graph->filters[k]) {
> +                        break;
> +                    }
> +                }

This looks quadratic in the number of filters in the graph.

> +
> +                if (!filters_state[k]) {
> +                    do_query = 0;
> +                    filters_init = 0;
> +                }
> +            }
> +
> +            if (do_query) {
> +                filters_state[i] = 1;
> +                if (graph->filters[i]->filter->query_formats)
> +                    graph->filters[i]->filter->query_formats(graph->filters[i]);
> +                else
> +                    avfilter_default_query_formats(graph->filters[i]);
> +            }
> +        }
> +    } while (!filters_init);
> +
> +    av_freep(&filters_state);

On the whole, it looks like you want to do the queries in dependency order.
There may be more efficient solutions.

>  
>      /* go through and merge as many format lists as possible */
>      for (i = 0; i < graph->filter_count; i++) {

Regards,

-- 
  Nicolas George
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