[M4IF Technotes] BIFStext

[Mikael Bourges-Sevenier]

Hi Karin,
-----Original Message-----
From: technotes-admin   lists.m4if.org [mailto:technotes-admin   lists.m4if.org]
On Behalf Of Karin Liebmann
Sent: Thursday, May 01, 2024 8:49 AM
To: technotes   lists.m4if.org
Subject: [M4IF Technotes] BIFStext
Hello everyone,
I have a question concerning BIFStext...
I would like to know if BIFStext is part of the MPEG-4 standard.. because I
didn't find any statement about it in the specification documents from the
MPEG homepage.
[Mikael Bourges-Sevenier] 
No it is not. It's a ad-hoc format derived from VRML 2.0 we used long before
XMT was specified. XMT-A is part of MPEG-4.
The standardized methode to create a mp4 szene with 3D, video and audio
content would be:
3D files as a x3d file - converting the x3d to xmt - including video and
audio - converting to a mp4 scene..
[Mikael Bourges-Sevenier] 
Yes but be careful: originally X3D had 2 DTDs called compact and compromise.
Today, X3D has chosen the compact DTD while XMT-A is based on compromise
DTD. The compromise DTD was chosen because of its straightforward conversion
to XML, which is not the case with the compact DTD. There exists some XSL
translators from compact to compromise DTD.
Then, you can use XSL translators from XMT-A to BifsText and Mp4Enc's
scripts; they are in IM1 distribution. 
the methode I used with my project was:
3D files as a vrml file- converting the vrml file to BIFStext- including
video and audio streams- converting to a mp4 szene with the help of the
mp4tool..
Is it right that this methode and the BIFStext is not MPEG-4 standard
conform? But it works!
[Mikael Bourges-Sevenier] 
It is the right way to do for MPEG-4 reference software (IM1). But it's not
the recommended "standard" way to do. 
Is BIFStext a solution created by ENST??
[Mikael Bourges-Sevenier] 
No, but note that ENST has also its own BifsText extensions....
Many MPEG companies use a sort of BifsText but as it is a proprietary
language, each has made its own extensions. So be careful: they might look
the same but they often have their own 'convensions'.
I used the second methode because I didn't find enough informations about
converting X3D to XMT...
Are this the only two methodes to create a mp4 scene?
[Mikael Bourges-Sevenier] 
If you use IM1, create your scene in BifsText, that's pretty simple.
Actually, you can use a VRML editor (e.g. VrmlPad) to create your scenes and
structure your scene as:
1- list of protos, if any
2- only one top node
3- list of routes, if any
Convert URL to object descriptors. Beware of supported audio/video types!
Create your Mp4Enc script and you should have your mp4 file.
In any case, the recommended practice should be: use an XML editor, create
your XMT-A scene and run your encoders. You can do that with IM1 as well by
using XSL translators before running the encoders.
Hope it helps,
Mike
I would be really glad to hear from someone of you!
Thanks very much in advance!
regards,
Karin
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