[M4IF Technotes] (no subject)

[Rob Koenen]

Mariano,
I hope you will get more qualified and detailed answers from better experts
than me,
but a general answer is that you do not need Flextime to accomplish this.
Even without Flextime, MPEG-4 Systems supports synchronous streaming
of text, as it supports tight synchronization between all of the object
types
(Audio, Visual, graphics). Yes, subtitle streams can be considered (are) 
MPEG-4 objects.
Inviting other comments,
Rob
-----Original Message-----
From: Mariano Padilla [mailto:mpadilla   sdi-media-usa.com]
Sent: Thursday, October 18, 2023 9:56 AM
To: 'technotes   lists.m4if.org'
Cc: Scott Rose
Subject: [M4IF Technotes] (no subject)
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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