[M4IF Technotes] Re: [M4IF Infolist] MPEG-4 questions

[Dave Singer]

Unofficial answers from one member...
At 3:35 PM +0200 8/3/01, Boris Rogge wrote:
>Hello all,
>
>First of all I would like to apologize for posting this message to the
>two reflectors, but since it's the first time I use this reflector I did
>not know the exact subjects of the different reflectors.
>
>I am preparing a paper on compairing multimedia formats and I am missing
>out on the following information regarding MPEG-4.
>
>1. Can extra multimedia formats be added to an MPEG-4 stream or does on
>have to use the MPEG-4 representation format?

Yes, additional streams can be added.  The file format, the systems 
layer, and the audio and video sub-systems all have code-points which 
would allow for such extensibility.
>2. Can an MPEG-4 stream dynamically adapt to a user or system profile?
>This means that for example the bitrate can dynamically be changed
>during a session.

This is possible, but much of the mechanism is a property of the 
transport system and its control protocol, rather than MPEG-4.
>3. What is the smallest time interval that can be represented within a
>MPEG-4 stream (ms, ns)?

The time stamp resolution (ticks per second) of MPEG-4 systems 
streams is configurable.  This is a 32-bit field, so in theory 
appallingly short periods can be accurately defined.
>
>Thank you very much for any answers regarding these topics.
>
>Boris Rogge
>Researcher
>Ghent University
>
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-- 
David Singer
Apple Computer/QuickTime
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