Are all of those ScopeRefs really ScopeRefs, or are some NestedScopes? Is the top level ScopeRef referencing another MobSlot or another Segment in a NestedScope?
A NestedScope allows a set of tracks (think of them as layers) to be placed within a single track. Quoting from the Edit Protocol: "When essence tracks are held within a NestedScope, the tracks are synchronized and a mapping to a single output track is specified." If you have n Segments in a NestedScope, the first n-1 are the input Segments (think of them as the layers), and the nth Segment defines what the "output" of the NestedScope should be at each point in time (ie. which of the layers (or an effect based on the layers) you would see).
A ScopeRef is used to reference another Segment within a NestedScope, or another MobSlot within a Mob, at the same point in time.
I received an input from Harry Plate some time ago that Avid's OperationGroup were being used as if they were NestedScopes (ie. the NestedScope is implied). We are trying to get that checked out at Avid. Are you seeing this too?
Regards,
Phil
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> Is the top level ScopeRef referencing another MobSlot or another Segment in a NestedScope?
>
Perhaps the latter, Phil. It's the most bizarre composition I've ever seen. The composition mob has 1 x EventMobSlot plus 2 x TimelineMobSlots (1 x picture track and 1 x timecode track). The picture track's Segment (where I'd normally expect to see a sequence) contains just a single Nested Scope. The Nested Scope then contains two segments - one of which is a sequence of 105 components (mostly SourceClips) and the other is another sequence of 19 components (mostly SourceRefs and Operation Groups, with a few transitions). I daresay it's all legal but it had me scratching my head for a while!! Re: your other question....
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> I received an input from Harry Plate some time ago that Avid's OperationGroup were being used as if they were NestedScopes
>
The short answer is yes - but it doesn't surprise me. Back in the days of OMF, the nested scope first appeared in OMFI-2 and it was used for the purpose of associating an effect with a source clip. Am I right in thinking that this is the purpose of an OperationGroup under AAF? If so, that probably explains the confusion.
Stuart's just asked me to email the AAF file to him because I can't make it work with my Debug version of AAFCOAPI.dll (even InfoDumper won't work, unless I use the Release DLL). It's a puzzler, all right!!
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and why is it a valid item to see in a sequence??
I've been sent an AAF file (originated from Avid Media Composer). Its composition mob contains a sequence whose components look something like this...
ScopeRef->ScopeRef->Transition->OperationGroup->OperationGroup->ScopeRef->SourceClip->Filler->SourceClip etc, etc.
What function do the ScopeRefs serve? Can anyone give me an example of what they're used for?
John,
Are all of those ScopeRefs really ScopeRefs, or are some NestedScopes? Is the top level ScopeRef referencing another MobSlot or another Segment in a NestedScope?
A NestedScope allows a set of tracks (think of them as layers) to be placed within a single track. Quoting from the Edit Protocol: "When essence tracks are held within a NestedScope, the tracks are synchronized and a mapping to a single output track is specified." If you have n Segments in a NestedScope, the first n-1 are the input Segments (think of them as the layers), and the nth Segment defines what the "output" of the NestedScope should be at each point in time (ie. which of the layers (or an effect based on the layers) you would see).
A ScopeRef is used to reference another Segment within a NestedScope, or another MobSlot within a Mob, at the same point in time.
I received an input from Harry Plate some time ago that Avid's OperationGroup were being used as if they were NestedScopes (ie. the NestedScope is implied). We are trying to get that checked out at Avid. Are you seeing this too?
Regards,
Phil
>
> Is the top level ScopeRef referencing another MobSlot or another Segment in a NestedScope?
>
Perhaps the latter, Phil. It's the most bizarre composition I've ever seen. The composition mob has 1 x EventMobSlot plus 2 x TimelineMobSlots (1 x picture track and 1 x timecode track). The picture track's Segment (where I'd normally expect to see a sequence) contains just a single Nested Scope. The Nested Scope then contains two segments - one of which is a sequence of 105 components (mostly SourceClips) and the other is another sequence of 19 components (mostly SourceRefs and Operation Groups, with a few transitions). I daresay it's all legal but it had me scratching my head for a while!! Re: your other question....
>
> I received an input from Harry Plate some time ago that Avid's OperationGroup were being used as if they were NestedScopes
>
The short answer is yes - but it doesn't surprise me. Back in the days of OMF, the nested scope first appeared in OMFI-2 and it was used for the purpose of associating an effect with a source clip. Am I right in thinking that this is the purpose of an OperationGroup under AAF? If so, that probably explains the confusion.
Stuart's just asked me to email the AAF file to him because I can't make it work with my Debug version of AAFCOAPI.dll (even InfoDumper won't work, unless I use the Release DLL). It's a puzzler, all right!!