[M4IF Technotes] (no subject)
Lim, Young-Kwon
young techway.co.kr
Fri Oct 19 14:09:02 EDT 2001
Dear Mario and all,
Basically, FlexTime provides additional flexible synchronization capability to MPEG-4. MPEG standards including MPEG-1, 2, and 4 are using absolute synchronization mechanism, that is, something shall be presented at the certain time. But FlexTime provides a way to define relative synchronization between medias, for example, the media A shall stop when the media B stops.
Conventional timing model is assuming the service requiring strict control of media and the terminal resource. But FlexTime is assuming the Web-like applications which is very flexible.
So you can choose one or another based on your requirement. As Rob explained subtitle can be an independent MPEG-4 object and you can synchronize it with other medias by using strict Timestamps or FlexTime. Please let me know if you need any detailed explanation.
Sincerely,
Young-Kwon Lim
----- Original Message -----
From: Mariano Padilla
To: 'technotes lists.m4if.org'
Cc: Scott Rose
Sent: Friday, October 19, 2023 1:55 AM
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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