User friendly warning message that gives out names of source and target formats

git-svn-id: file:///var/local/repositories/mplayer/trunk/libswscale@30370 b3059339-0415-0410-9bf9-f77b7e298cf2

yuv2rgb.c

@@ -530,7 +530,7 @@ SwsFunc ff_yuv2rgb_get_func_ptr(SwsContext *c)
     if (t)
         return t;
 
-    av_log(c, AV_LOG_WARNING, "No accelerated colorspace conversion found.\n");
+    av_log(c, AV_LOG_WARNING, "No accelerated colorspace conversion found from %s to %s.\n", sws_format_name(c->srcFormat), sws_format_name(c->dstFormat));
 
     switch (c->dstFormat) {
     case PIX_FMT_RGB48BE: