Re: [9fans] dataflow programming from shell interpreter

[Skip Tavakkolian <9nut@9netics.com>]

> Aren't DirectShow filter graphs and programs like GraphStudio/GraphEdit one
> possible answer to the video processing question? Filter graphs can be
> generated by any program, GUI or CLI, and fed to DirectShow provided one
> learns the in and out of generating them.

DirectShow is COM; source/mux/transform/sink filters must provide a
number of interfaces (e.g.  IFileSinkFilter); other components
(e.g.  GraphBuilder) are there to make it easier to hook them
together.

i don't think a direct mapping of COM to Plan 9 fs model is
unnecessary.  for example, instead of mapping every control or
configuration interface and method to synthetic directories and files,
a single ctl file will do.  something like this seems sufficient:

	/ctl		# e.g. accepts run, stop, etc.  returns: paused, #outputs, config, etc.
	/event	# instead of callback notification
	/ipin/clone
	/ipin/n/ctl
	/ipin/n/event
	/ipin/n/data
	/opin/clone
	/opin/n/ctl
	/opin/n/event
	/opin/n/data

for a special purpose kernel one could add a driver and a fancy new
hook syscall (similar to pushssl and '#D') that would hook two fd's
together to eliminate the need for a user proc to transfer between
ipin/?/data and opin/?/data.