Requesting a simple example using fdsrc and fdsink

[Piper984]

Hi:
My first message had some [raw] tags (via the Nabble site ) around the bash
commands I provided and those look to have been removed from the email
digest.  So I'm reposting my request without those tags, as I think most
GStreamers rely on the email digests.  Also fixed a typo. :)

---START REPOST---

Hello forum, 

I have a few Gstreamer based projects coming up where I'd like to use
stdin/stdout or named pipes to sink and source video.  I've not had much
luck in getting a simple hello world type pipeline working. Hopefully
someone can take a look at this with me and give me some pointers. 

I'd like to see how I could take a very simple pipeline like this (which
works find on Ubuntu 14.04)... 

gst-launch-1.0 -e -v videotestsrc is-live=true horizontal-speed=1 !
autovideosink sync=false

... and split into two parts. Part one: pipe the output of videotestsrc to
stdout, and then Part two: pipe stdin to the autovideosink element. 

I tried this: 

gst-launch-1.0 -e -v videotestsrc is-live=true horizontal-speed=1 ! fdsink |
gst-launch-1.0 -e -v fdsrc fd=0 ! autovideosink

But when I try this I get the following error message: 

Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
Got context from element 'autovideosink0-actual-sink-glimage':
gst.gl.GLDisplay=context, gst.gl.GLDisplay=(GstGLDisplay)"\(GstGLDisplay\)\
gldisplay0";
ERROR: from element /GstPipeline:pipeline0/GstFdSrc:fdsrc0: Internal data
flow error.
Additional debug info:
gstbasesrc.c(2933): void gst_base_src_loop(GstPad *) ():
/GstPipeline:pipeline0/GstFdSrc:fdsrc0:
streaming task paused, reason not-negotiated (-4)
ERROR: pipeline doesn't want to preroll.
Setting pipeline to NULL ...
Freeing pipeline ...

I've tried searching for better syntax but so far no luck in getting
anything to work.  If someone could take a look and point me in the right
direction it would be super helpful.  I have a few apps I need to develop
where using named pipes is going to be very handy so hopefully figuring out
the proper syntax and usage of fdsrc and fdsink will get me to where I need
to be. 


Thanks and regards!



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