mpeg12enc: always write closed gops for intra only outputs

Reviewed-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: Marton Balint <cus@passwd.hu>

libavcodec/mpeg12enc.c

@@ -350,7 +350,7 @@ static void mpeg1_encode_sequence_header(MpegEncContext *s)
         put_bits(&s->pb, 1, 1);
         put_bits(&s->pb, 6, (uint32_t)((time_code / fps) % 60));
         put_bits(&s->pb, 6, (uint32_t)((time_code % fps)));
-        put_bits(&s->pb, 1, !!(s->flags & CODEC_FLAG_CLOSED_GOP));
+        put_bits(&s->pb, 1, !!(s->flags & CODEC_FLAG_CLOSED_GOP) || s->intra_only);
         put_bits(&s->pb, 1, 0);                     // broken link
     }
 }

tests/ref/lavf/mxf_d10

-28cf73e6d35a8f7aba30c0ed2bd84924 *./tests/data/lavf/lavf.mxf_d10
+838b732d832dcf40b0eb9944bc6d8f55 *./tests/data/lavf/lavf.mxf_d10
 5330989 ./tests/data/lavf/lavf.mxf_d10
 ./tests/data/lavf/lavf.mxf_d10 CRC=0x6c74d488