[Videomgmt] A simple proposal

["Ray, Robert" <[e-mail]>]

I thought I'd follow up on Larry's email about keeping things simple.
At the very heart of this industry seems to be two elements: inputs and
outputs.  The sole universal operation is to connect an input to an
output (a "take").

For some of the industry, the operation needs to be performed in concert
with a very specific event, the vertical interval, specified via a
timecode (hours, minutes, seconds, frame #).  For others, the operation
needs to be performed based upon some external, non-time-based, event.
For many, the operation simply needs to be performed as soon as
possible. 

Additionally, for most of the industry, the operation needs to be
performed on several inputs and several outputs simultaneously.

Examples:

1.  In a composite video router, an input can be connected to zero or
more outputs.

2.  In an RGB video router, a collection of inputs needs to be connected
to a similar collection of outputs; red input to red output, green input
to green output, etc.

3.  In a KVM switch, three inputs must be simultaneously switched to
three outputs.  A keyboard input must be connected to a keyboard output,
a video input must be connected to a video output, a mouse input must be
connected to a mouse output.

4.  An audio processor may include audio mixing capabilities, where more
than one input is connected to an one output (or more than one output).


5.  A video processor may provide mixing of video inputs to provide an
output.  For example, keys, wipes, and fades.

6.  All of the above might be controlled via automation equipment,
perhaps an audio router than switches to a 

Each of the elements (inputs, outputs) can have characteristics which
are highly dependent upon the nature of the element.  An input may be an
audio signal, it may be an analog video signal, it may be a serial
signal (i.e. mouse movement or an RS-422 port), it may 5.1 digital audio
signal, etc.  

Abstract groupings of these elements may have characteristics which are
distinct from the individual elements.  For example, combining several
audio inputs and video inputs to produce an output signal (say,
down-conversion of HD video + 6 channel digital audio signal for output
on an analog monitor) would have characteristics that differ from a KVM
group (keyboard 1, video 1, mouse 1).

Attempting to provide a MIB which is all things to all of these
different would certainly consume a lot of time, produce a very complex
document, and would never be implemented.  

However, having a collection of MIBs which as a whole accomplish the
same thing would seem far easier (as long as they are developed
cohesively).  Viewed as objects (OO), a base class would be inputs and
outputs with a method to associate the two.  A derived class would
overide the method to perform the method based upon some external event
(i.e. a timecode).  Other derived classes would augment the base object
with characterics specific to the signal (clock, encoding, etc.).
Another class would provide groupings (e.g., inputGroups, outputGroups)
and a method of associating the groups.

To summarize: at the most basic level, we need 

1) inputs
2) outputs
3) a method to connect the two

The ability to retrieve the current connections would seem appropriate
for this class although this becomes murky when one considers the
difference between one-to-one (simple switch), many-to-one (simple
mixer), one-to-many (distribution router), or many-to-many.  It may be
best to place this capability into a derived class.

The single characteristic that may be appropriate at this level
(considering the widely varying nature of the inputs and outputs) is
signal presence.  

The ability to generate notifications when an input is connected (or
disconnected) from an output would seem appropriate for this class.  If
so, however, the ability to control, throttle, or disable the generation
of this notification would seem necessary, especially if a user is more
interested in the occurrence of operations between complex groupings.
Similarly, a notification indicating change in signal presence at an
input or output would seem appropriate for this class.

Thoughts?

I will convert the above stream into a simple MIB for futher discussion
if anyone is interested.  Larry?  Others?

Regards,
Bob Ray


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