Do not try to set a video standard unless "-tvstd" is specified

Originally committed as revision 9088 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffmpeg.c

@@ -182,7 +182,7 @@ static FILE *fvstats;
 static int rate_emu = 0;
 
 static int  video_channel = 0;
-static char *video_standard = "ntsc";
+static char *video_standard;
 
 static int audio_volume = 256;
 
@@ -3834,6 +3834,8 @@ int main(int argc, char **argv)
 
     av_free(opt_names);
 
+    av_free(video_standard);
+
 #ifdef CONFIG_POWERPC_PERF
     extern void powerpc_display_perf_report(void);
     powerpc_display_perf_report();