fix endianness of time code, and calculate it in fields, according to specs

Originally committed as revision 16730 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/gxfenc.c

@@ -361,13 +361,11 @@ static int gxf_write_flt_packet(ByteIOContext *pb, GXFContext *ctx)
 static int gxf_write_umf_material_description(ByteIOContext *pb, GXFContext *ctx)
 {
     // XXX drop frame
-    int fps = ctx->sample_rate / 2;
-    int frames = ctx->nb_frames / 2;
     uint32_t timecode =
-        frames % fps             << 24 | // frames
-        frames / fps % 60        << 16 | // seconds
-        frames / fps * 60 % 60   <<  8 | // minutes
-        frames / fps * 3600 % 24 <<  3;  // hours
+        ctx->nb_frames / ctx->sample_rate * 3600 % 24 << 27 | // hours
+        ctx->nb_frames / ctx->sample_rate * 60 % 60   << 16 | // minutes
+        ctx->nb_frames / ctx->sample_rate % 60        <<  8 | // seconds
+        ctx->nb_frames % ctx->sample_rate;                    // fields
 
     put_le32(pb, ctx->flags);
     put_le32(pb, ctx->nb_frames); /* length of the longest track */

tests/libav.regression.ref

@@ -27,7 +27,7 @@ af78858062599fcbba049e4a02588a15 *./tests/data/b-libav.mov
 913b6199765b1dcba196706574621c2f *./tests/data/b-libav.dv
 3600000 ./tests/data/b-libav.dv
 ./tests/data/b-libav.dv CRC=0x7787e173
-ede81f26a3a68228d01124def788549d *./tests/data/b-libav.gxf
+8441d11ebee0465f1a672586485f3506 *./tests/data/b-libav.gxf
 805996 ./tests/data/b-libav.gxf
 ./tests/data/b-libav.gxf CRC=0x9c06676e
 66a6584f9e83e8ea3af822a3ba71fbbe *./tests/data/b-libav.nut