ffmpeg: rewrite vsync / notimestamps handling

The qatar implementation makes no sense.
a muxer without timestamps is constant fps thus needs vsync.
the crc/mp5 are special cases that have timestamps yet allow any
nonsensical timestamps.
raw (yuv/rgb) video is constant fps thus needs vsync too.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

ffmpeg.c

@@ -1246,8 +1246,7 @@ static void do_video_out(AVFormatContext *s,
 
     format_video_sync = video_sync_method;
     if (format_video_sync < 0)
-        format_video_sync = (s->oformat->flags & AVFMT_NOTIMESTAMPS) ? 0 :
-                            (s->oformat->flags & AVFMT_VARIABLE_FPS) ? 2 : 1;
+        format_video_sync = (s->oformat->flags & AVFMT_VARIABLE_FPS) ? ((s->oformat->flags & AVFMT_NOTIMESTAMPS) ? 0 : 2) : 1;
 
     if (format_video_sync) {
         double vdelta = sync_ipts - ost->sync_opts + duration;

tests/ref/lavf/gxf

 346d38d330ab5cb0caa6b5537167bc0d *./tests/data/lavf/lavf.gxf
 796392 ./tests/data/lavf/lavf.gxf
-./tests/data/lavf/lavf.gxf CRC=0x345f86eb
+./tests/data/lavf/lavf.gxf CRC=0x102918fd