[gst-devel] About spider...

Benjamin Otte in7y118 at public.uni-hamburg.de
Thu Jul 10 11:18:07 CEST 2003

On Wed, 9 Jul 2003, Francis Labonte wrote:

> Hi,
> using the following command:
> gst-launch filesrc location=./audio.wav ! wavparse ! audioscale
> frequency=8000 ! spider ! myAudioCodec ! filesink location=./out.raw
> I try to use the spider to identify the element to be inserted between the
> output of the audioscale and an audio codec.
> The audio codec accept 8kHz mono input and is working fine.
> Everything work fine if I connect the audioscale to the audiocodec.  If I
> insert the spider between these 2 elements, then the stero2mono is allways
> inserted, even if wav file contains mono.
Spider is quite a bit broken in what it does and how it does it. You must
be very nice to spider or it will do evil things ;)

> Questions:
> - Did the spider try a direct connection between the 2 pads to connect
> first?  Can it act as a passtrought??
I think it can (though there was a time once when it didn't try.

> - If not, how can I do it?
> - Why the stereo2mono filter is allays inserted, even if the input is mono?
Because spider decides which elements to use in the wrong way. It looks at
the possible capabilities and not at the actual ones when they become
available. Therefore it sees stereo2mono as the best way to plug any
output from audioscale to your input.
I think an ideal autoplugger would do what you want, but spider is not
ideal. If you want to use this pipeline you'll have to hack around it I
think (If someone knows a better way, please tell it). Or you can write a
new autoplugger. We all want one :)


PS: Spider was the first thing I did for GStreamer and the first thing I
did with C. It works exactly like one would expect such stuff to work ;/

> Thank you
> Francis Labonte
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