libavformat/mpegts: expose raw packet size

We cannot easily determine if an mpeg TS's packet size is DVHS, FEC
or so on, for that we need to expose the internal raw_packet_size
field.
Signed-off-by: NAnton Khirnov <anton@khirnov.net>

libavformat/mpegts.c

@@ -134,6 +134,8 @@ struct MpegTSContext {
 static const AVOption options[] = {
     {"compute_pcr", "Compute exact PCR for each transport stream packet.", offsetof(MpegTSContext, mpeg2ts_compute_pcr), AV_OPT_TYPE_INT,
      {.i64 = 0}, 0, 1, AV_OPT_FLAG_DECODING_PARAM },
+    {"ts_packetsize", "Output option carrying the raw packet size.", offsetof(MpegTSContext, raw_packet_size), AV_OPT_TYPE_INT,
+     {.i64 = 0}, 0, 0, AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_EXPORT | AV_OPT_FLAG_READONLY },
     { NULL },
 };