Usefulness of graphical pipeline editors and/or visualizers

[Carlos Rafael Giani]

Hello,

I've seen several attempts at writing graphical pipeline editors,
similar to DirectShow's GraphEdit: http://i.imgur.com/9C1Xl.png

But I wonder how useful it would really be. I only see the following use
cases:

1) Visualizing complex pipelines (a large gst-launch line for example),
to see what's wrong with the construction. Kind of like what
GST_DEBUG_DUMP_DOT_DIR does, except interactive.

2) As a tool for file format conversions and (de)muxing. This is what
GraphEdit is often used for.

3) As an alternative to gst-launch for pipeline prototyping. Even though
gst-launch works fine, complex pipelines can benefit from a visual
representation.

Now, as discussed in the chat, the main problem is that more complex
pipelines usually are at least partially dynamic. I guess that seriously
limits what such a tool could do.

Also, what about sometimes pads (like decobin2 has)? I can imagine some
highlevel abstractions on a per-elementclass basis, but that requires a
lot of work.

GraphEdit works because the DirectShow pins operate differently. For
example, a demuxer always has one unconnected pin. When this pin is
connected, it creates a new pin etc. Of course this works much better
with visual tools. (GStreamer's sometimes system is nicer to code with,
though.)

Any thoughts on this?
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[Mike Mitchell]

Having spent many hours debugging gst-launch command lines, I think this would be very useful.  The purpose you missed is that knowing how pads connect, assisting in caps negotiation, knowing the syntax of gst-launch properties would make gstreamer much easier to use for most people. Even if I intend to code a pipeline by hand, I always build it with gst-launch first. 

Such a tool could also provide an interface for a live profiler and debugger which would be priceless for things like OpenCv development. 

There was a reasonably good tool start, but it got deprecated when the XML descriptor got deprecated. http://code.google.com/p/gst-editor/ Seems to me the challenge is that such a tool would need to build gst-launch commands, and the syntax is a bit cryptic and unstructured.  Another attempt at rendering live pipelines is here: https://launchpad.net/firtree/

Mike Mitchell

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