avformat/movenc: avoid floats in width/height/aspect ratio computations

This avoids the possibility for rounding/precision differences between platforms
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/movenc.c

@@ -2368,10 +2368,12 @@ static int mov_write_tkhd_tag(AVIOContext *pb, MOVMuxContext *mov,
             avio_wb32(pb, track->enc->width << 16);
             avio_wb32(pb, track->height << 16);
         } else {
-            double sample_aspect_ratio = av_q2d(st->sample_aspect_ratio);
-            if (!sample_aspect_ratio || track->height != track->enc->height)
-                sample_aspect_ratio = 1;
-            avio_wb32(pb, sample_aspect_ratio * track->enc->width * 0x10000);
+            int64_t track_width_1616 = av_rescale(st->sample_aspect_ratio.num,
+                                                  track->enc->width * 0x10000LL,
+                                                  st->sample_aspect_ratio.den);
+            if (!track_width_1616 || track->height != track->enc->height)
+                track_width_1616 = track->enc->width * 0x10000;
+            avio_wb32(pb, track_width_1616);
             avio_wb32(pb, track->height * 0x10000);
         }
     } else {