The "switch-track" command can be used to switch tracks. The "type"
argument selects which track type to change (can be "audio", "video",
or "text"). The "index" argument selects which track of this type
to use: it can be either a number, which will be the Nth track of
the given type, or a number with a "+" or "-" prefix, which means
a relative change (eg, "+1" means "next track", "-1" means "previous
track").
Conflicts:
validate/gst/validate/gst-validate-scenario.c
Various type of object should be able to do some reporting, so we have
to make sure all the code to do that is in one place. Creating an interface
makes it simple to share information and it avoid to have a baseclass for
something that is not actually important enough to create a baseclass.
Conflicts:
gst/qa/gst-qa-pad-monitor.c
A scenario correspond to a suite of action to execute on a pipeline,
for the time being, we only support seeking the pipeline, but in the
future we can imagine doing some queries, setting pipeline state, etc...
The scenario can be loaded thanks to the GST_QA_SCENARIO environment
variable, making it usable with any existant application, in case, the
application can be used interactively, the user should either, not load
any scenario or let the application run without interacting with it.
