libavfilter/vf_owdenoise.c: skip processing when strength is 0

It is practical to de-noise only on luma while keeping chroma unchanged.

However, libavfilter/vf_owdenoise.c always do the Wavelet transform/retransform on all 3 channels without check whether chroma_strength is 0.

Thus I make this patch. De-noise on Y only for yuv420 is now 1.5 times faster.
Signed-off-by: Yuuki Galaxy <galaxy001@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavfilter/vf_owdenoise.c

@@ -222,7 +222,6 @@ static void filter(OWDenoiseContext *s,
 
 static int filter_frame(AVFilterLink *inlink, AVFrame *in)
 {
-    int direct = 0;
     AVFilterContext *ctx = inlink->dst;
     OWDenoiseContext *s = ctx->priv;
     AVFilterLink *outlink = ctx->outputs[0];
@@ -231,8 +230,14 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
     const int ch = AV_CEIL_RSHIFT(inlink->h, s->vsub);
 
     if (av_frame_is_writable(in)) {
-        direct = 1;
         out = in;
+
+        if (s->luma_strength > 0)
+            filter(s, out->data[0], out->linesize[0], in->data[0], in->linesize[0], inlink->w, inlink->h, s->luma_strength);
+        if (s->chroma_strength > 0) {
+            filter(s, out->data[1], out->linesize[1], in->data[1], in->linesize[1], cw,        ch,        s->chroma_strength);
+            filter(s, out->data[2], out->linesize[2], in->data[2], in->linesize[2], cw,        ch,        s->chroma_strength);
+        }
     } else {
         out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
         if (!out) {
@@ -240,13 +245,20 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
             return AVERROR(ENOMEM);
         }
         av_frame_copy_props(out, in);
-    }
 
-    filter(s, out->data[0], out->linesize[0], in->data[0], in->linesize[0], inlink->w, inlink->h, s->luma_strength);
-    filter(s, out->data[1], out->linesize[1], in->data[1], in->linesize[1], cw,        ch,        s->chroma_strength);
-    filter(s, out->data[2], out->linesize[2], in->data[2], in->linesize[2], cw,        ch,        s->chroma_strength);
+        if (s->luma_strength > 0) {
+            filter(s, out->data[0], out->linesize[0], in->data[0], in->linesize[0], inlink->w, inlink->h, s->luma_strength);
+        } else {
+            av_image_copy_plane(out->data[0], out->linesize[0], in ->data[0], in ->linesize[0], inlink->w, inlink->h);
+        }
+        if (s->chroma_strength > 0) {
+            filter(s, out->data[1], out->linesize[1], in->data[1], in->linesize[1], cw, ch, s->chroma_strength);
+            filter(s, out->data[2], out->linesize[2], in->data[2], in->linesize[2], cw, ch, s->chroma_strength);
+        } else {
+            av_image_copy_plane(out->data[1], out->linesize[1], in ->data[1], in ->linesize[1], inlink->w, inlink->h);
+            av_image_copy_plane(out->data[2], out->linesize[2], in ->data[2], in ->linesize[2], inlink->w, inlink->h);
+        }
 
-    if (!direct) {
         if (in->data[3])
             av_image_copy_plane(out->data[3], out->linesize[3],
                                 in ->data[3], in ->linesize[3],