[AG-DEV] multi-input capture (was AccessGrid 3: What information is available)

[Andrew Swan]

Andrew Rowley wrote:
> > be possible to take advantage of a multi-input vic since there
> > is a 1-to-1 mapping of "resources" (i.e., video capture devices)
> > to node services.  if that is incorrect, i'd be interested in a
> > clarification.
> 
> [...]
> In summary, it would be useful to have a video tool that sends and receives
> all the video streams so that only one instance need be opened on any
> system, and that instance will cope in both a unicast and multicast
> situation.

sorry, let me clarify the question.  as i understand the code,
one of the methods in the AGService api is SetResource(), which
tells an AGService which resource to use, where a resource is
an i/o device like a video capture card for a video service,
or a sound card for an audio serivce.  the way these resources
are discovered is different in 2.3 and in the cvs head but in
either case, only a single resource may be assigned to an
instance of a service.  this assignment is done manually by the
node operator from the "Select Resource" dialog that is presented
when adding a new service instance.

so, if we had a multi-input encoder, it wouldn't be possible to
write a MultipleInputVideoProducerService since only a single
resource (i.e., video capture card) could be assigned to an
instance of the service.  of course, the encoder could attempt
to open and encode from each video capture card that is present
and just ignore the configuration done from the NodeManagement
app but that doesn't seem like a very good idea.

i think this explanation is correct -- can somebody who is more
familiar with the code either confirm that this is right or 
explain what has been overlooked?

assuming that this evaluation is correct, do people think the
simplest solution be to make headless capture work correctly?
or would it be better to somehow change the abstractions in the
core toolkit?

-Andrew