Unset variable fps for mov and mp4 muxer, they support it

but timestamps must start at 0 currently, and this causes sync
problem.

Originally committed as revision 25805 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/movenc.c

@@ -2215,7 +2215,7 @@ AVOutputFormat mov_muxer = {
     mov_write_header,
     ff_mov_write_packet,
     mov_write_trailer,
-    .flags = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS,
+    .flags = AVFMT_GLOBALHEADER,
     .codec_tag = (const AVCodecTag* const []){codec_movvideo_tags, codec_movaudio_tags, 0},
 };
 #endif
@@ -2247,7 +2247,7 @@ AVOutputFormat mp4_muxer = {
     mov_write_header,
     ff_mov_write_packet,
     mov_write_trailer,
-    .flags = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS,
+    .flags = AVFMT_GLOBALHEADER,
     .codec_tag = (const AVCodecTag* const []){ff_mp4_obj_type, 0},
 };
 #endif