[M4IF Technotes] Where is the specification for...

[Mathijn Elhorst]

Hi,
You are looking at data for the BIFS (Binary Format For Scenes) scene 
graph data version 1 (obj. descr. 1). A  working document 
(14496-1:2002)  describing the systems part of MPEG-4 including BIFS, 
can be found here:
http://mpeg.telecomitalialab.com/working_documents/mpeg-04/systems/3rd_edition_wd.zip
The bytes correspond to the following scene-graph:
OrderedGroup {
    children Shape {
        appearance Appearance {
            texture MovieTexture {
                url "od:3"
            }
        }
        geometry Bitmap {
        }
    }
}
which is the simplest way to start playing a video found in the track 
with object descriptor id 3
Regards
Mathijn
Stage NexVision wrote:
>Hi guys,
>
>
>   I'm trying to understand what is in the "mdat" atom, and concerning video
>information or audio information, I've found the corresponding specification
>However, I have some data (of 0x0A length) that are pointed by an trak
>definition containing the corresponding descriptor (in esds atom) that is of
>type "Object descriptor = 1 (Scene); and Stream Type = 3 (Scene)"
>
>In the mdat atom, the corresponding data are
>C0 11 A4 CD 54 11 40 3D 04 C0
>
>I cannot recognize what type it is (not an object descriptor, or neither an
>atom)
>
>If you know how to understand these bytes, please tell me.
>Thank you.
>
>
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