@@ -24,6 +24,7 @@

 #include <string.h>

 #include "libavutil/audioconvert.h"

+#include "libavutil/pixdesc.h"

 #include "avfilter.h"

 #include "avfiltergraph.h"

 #include "internal.h"

@@ -252,13 +253,26 @@ static int query_formats(AVFilterGraph *graph, AVClass *log_ctx)

     return 0;

 }

-static void pick_format(AVFilterLink *link)

+static void pick_format(AVFilterLink *link, AVFilterLink *ref)

 {

     if (!link || !link->in_formats)

         return;

+    if (link->type == AVMEDIA_TYPE_VIDEO) {

+        if(ref && ref->type == AVMEDIA_TYPE_VIDEO){

+            int has_alpha= av_pix_fmt_descriptors[ref->format].nb_components % 2 == 0;

+            enum PixelFormat best= PIX_FMT_NONE;

+            int i;

+            for (i=0; i<link->in_formats->format_count; i++) {

+                enum PixelFormat p = link->in_formats->formats[i];

+                best= avcodec_find_best_pix_fmt2(best, p, ref->format, has_alpha, NULL);

+            }

+            link->format = best;

+        }else

+            link->format = link->in_formats->formats[0];

+    }

+

     link->in_formats->format_count = 1;

-    link->format = link->in_formats->formats[0];

     avfilter_formats_unref(&link->in_formats);

     avfilter_formats_unref(&link->out_formats);

@@ -324,11 +338,21 @@ static void pick_formats(AVFilterGraph *graph)

     for (i = 0; i < graph->filter_count; i++) {

         AVFilterContext *filter = graph->filters[i];

-

-        for (j = 0; j < filter->input_count; j++)

-            pick_format(filter->inputs[j]);

-        for (j = 0; j < filter->output_count; j++)

-            pick_format(filter->outputs[j]);

+        if (filter->input_count && filter->output_count) {

+            for (j = 0; j < filter->input_count; j++)

+                pick_format(filter->inputs[j], NULL);

+            for (j = 0; j < filter->output_count; j++)

+                pick_format(filter->outputs[j], filter->inputs[0]);

+        }

+    }

+    for (i = 0; i < graph->filter_count; i++) {

+        AVFilterContext *filter = graph->filters[i];

+        if (!(filter->input_count && filter->output_count)) {

+            for (j = 0; j < filter->input_count; j++)

+                pick_format(filter->inputs[j], NULL);

+            for (j = 0; j < filter->output_count; j++)

+                pick_format(filter->outputs[j], NULL);

+        }

     }

 }