avcodec/videotoolbox: choose AYUV pixel format when ideal

Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/videotoolbox.c

@@ -1180,11 +1180,10 @@ static enum AVPixelFormat videotoolbox_best_pixel_format(AVCodecContext *avctx)
     if (!descriptor)
         return AV_PIX_FMT_NV12; // same as av_videotoolbox_alloc_context()
 
+    depth = descriptor->comp[0].depth;
 
     if (descriptor->flags & AV_PIX_FMT_FLAG_ALPHA)
-        return AV_PIX_FMT_AYUV64;
+        return (depth > 8) ? AV_PIX_FMT_AYUV64 : AV_PIX_FMT_AYUV;
-
-    depth = descriptor->comp[0].depth;
 
 #if HAVE_KCVPIXELFORMATTYPE_444YPCBCR16BIPLANARVIDEORANGE
     if (depth > 10)