avfilter/avfilter: #if ff_tlog_link() away when empty

It is currently calling av_channel_layout_describe()
unnecessarily.

Reviewed-by: Nicolas George <george@nsup.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavfilter/avfilter.c

@@ -381,6 +381,7 @@ int avfilter_config_links(AVFilterContext *filter)
     return 0;
 }
 
+#ifdef TRACE
 void ff_tlog_link(void *ctx, AVFilterLink *link, int end)
 {
     if (link->type == AVMEDIA_TYPE_VIDEO) {
@@ -404,6 +405,7 @@ void ff_tlog_link(void *ctx, AVFilterLink *link, int end)
                 end ? "\n" : "");
     }
 }
+#endif
 
 int ff_request_frame(AVFilterLink *link)
 {

libavfilter/internal.h

@@ -268,7 +268,11 @@ void ff_command_queue_pop(AVFilterContext *filter);
 
 char *ff_get_ref_perms_string(char *buf, size_t buf_size, int perms);
 
+#ifdef TRACE
 void ff_tlog_link(void *ctx, AVFilterLink *link, int end);
+#else
+#define ff_tlog_link(ctx, link, end) do { } while(0)
+#endif
 
 /**
  * Append a new input/output pad to the filter's list of such pads.