Merge commit '88b160a457e491cb9e014630ef5387ad3500258e'

* commit '88b160a457e491cb9e014630ef5387ad3500258e':
  avfilter: Return more meaningful error codes

Conflicts:
	libavfilter/avfilter.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/avfilter.c

@@ -135,7 +135,7 @@ int avfilter_link(AVFilterContext *src, unsigned srcpad,
 
     if (src->nb_outputs <= srcpad || dst->nb_inputs <= dstpad ||
         src->outputs[srcpad]      || dst->inputs[dstpad])
-        return -1;
+        return AVERROR(EINVAL);
 
     if (src->output_pads[srcpad].type != dst->input_pads[dstpad].type) {
         av_log(src, AV_LOG_ERROR,
@@ -381,7 +381,7 @@ int ff_poll_frame(AVFilterLink *link)
     for (i = 0; i < link->src->nb_inputs; i++) {
         int val;
         if (!link->src->inputs[i])
-            return -1;
+            return AVERROR(EINVAL);
         val = ff_poll_frame(link->src->inputs[i]);
         min = FFMIN(min, val);
     }