avfilter/avfiltergraph: Implement and use find_best_sample_fmt_of_2()

Similar to the pixel format code

Fixes Ticket3847
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavfilter/avfiltergraph.c

@@ -631,6 +631,40 @@ static int query_formats(AVFilterGraph *graph, AVClass *log_ctx)
     return 0;
 }
 
+static int get_fmt_score(enum AVSampleFormat dst_fmt, enum AVSampleFormat src_fmt)
+{
+    int score = 0;
+
+    if (av_sample_fmt_is_planar(dst_fmt) != av_sample_fmt_is_planar(src_fmt))
+        score ++;
+
+    if (av_get_bytes_per_sample(dst_fmt) < av_get_bytes_per_sample(src_fmt)) {
+        score += 100 * (av_get_bytes_per_sample(src_fmt) - av_get_bytes_per_sample(dst_fmt));
+    }else
+        score += 10  * (av_get_bytes_per_sample(dst_fmt) - av_get_bytes_per_sample(src_fmt));
+
+    if (av_get_packed_sample_fmt(dst_fmt) == AV_SAMPLE_FMT_S32 &&
+        av_get_packed_sample_fmt(src_fmt) == AV_SAMPLE_FMT_FLT)
+        score += 20;
+
+    if (av_get_packed_sample_fmt(dst_fmt) == AV_SAMPLE_FMT_FLT &&
+        av_get_packed_sample_fmt(src_fmt) == AV_SAMPLE_FMT_S32)
+        score += 2;
+
+    return score;
+}
+
+static enum AVSampleFormat find_best_sample_fmt_of_2(enum AVSampleFormat dst_fmt1, enum AVSampleFormat dst_fmt2,
+                                                     enum AVSampleFormat src_fmt)
+{
+    int score1, score2;
+
+    score1 = get_fmt_score(dst_fmt1, src_fmt);
+    score2 = get_fmt_score(dst_fmt2, src_fmt);
+
+    return score1 < score2 ? dst_fmt1 : dst_fmt2;
+}
+
 static int pick_format(AVFilterLink *link, AVFilterLink *ref)
 {
     if (!link || !link->in_formats)
@@ -650,6 +684,19 @@ static int pick_format(AVFilterLink *link, AVFilterLink *ref)
                    av_get_pix_fmt_name(ref->format), has_alpha);
             link->in_formats->formats[0] = best;
         }
+    } else if (link->type == AVMEDIA_TYPE_AUDIO) {
+        if(ref && ref->type == AVMEDIA_TYPE_AUDIO){
+            enum AVSampleFormat best= AV_SAMPLE_FMT_NONE;
+            int i;
+            for (i=0; i<link->in_formats->nb_formats; i++) {
+                enum AVSampleFormat p = link->in_formats->formats[i];
+                best = find_best_sample_fmt_of_2(best, p, ref->format);
+            }
+            av_log(link->src,AV_LOG_DEBUG, "picking %s out of %d ref:%s\n",
+                   av_get_sample_fmt_name(best), link->in_formats->nb_formats,
+                   av_get_sample_fmt_name(ref->format));
+            link->in_formats->formats[0] = best;
+        }
     }
 
     link->in_formats->nb_formats = 1;