[M4IF Technotes] (no subject)

[Mariano Padilla]

We at SDI Media USA specialize in Theatrical, DVD, Home Video and broadcast
subtitles and captions for over 40 languages. Naturally we are looking at
how subtitles are synchronized in MPEG-4.
Specifically we are wondering the synchronization of subtitles on MPEG 4
stream. In the MPEG4 overview in section 8.3.2, 'The FlexTime model allows
the content author to express synchronization among MPEG-4 objects with
streams or stream segments, by assigning temporal relationships among them.'
then the following questions: 
1) Are subtitle streams to be synchronized considered MPEG objects? 
2) If the subtitle streams to be synchronized are MPEG objects, do they have
to behave according to the SMIL text guidelines in section 4.2.2 of the
overview? 
3) If 2 above is true, then does SMIL used in MPEG4 allow millisecond or
frame-accurate synchronization with the video? 
4) If there is no text/SMIL synchronization of multinational subtitles, how
can synchronization of external images be achieved? Is it similar to the
MPEG2/DVD model? 
Mariano J. Padilla
Director of IT/R&D
SDI Media USA
T 323-602-5406
F 323-602-5450
www.sdi-media-usa.com
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