GStreamer -Dynamic pipelines : Issue with adding a new element in the pipeline

[Michael MacIntosh]

Hey,

Generally you get "WRONG_HIERARCHY" when you try to link an element that 
doesn't belong to the pipeline you are tying to link to.  I don't see 
you adding it to the pipeline in that snippet. That needs to be done 
before you attempt to link it.

I'm not sure about the python API, but with the C Api, you need to pass 
either user_data or a context when you attach the probe, which is 
probably why self is not working in your method.  I would also probably 
use a static function for the sake of simplicity.

Best of luck!


On 8/17/2018 4:08 AM, vk_gst wrote:
> Hi,
>
> Below is my pipeline  :
> v4l2src -> h264parse -> avdec_h264 -> identity ->glupload -> glcolorconvert
> -> gltransformation -> glimagesink.
>
> Based on the user input(keyboard input), I set the property
> "drop-probability" to 1 or 0. Basically, just toggling it based on the count
> of input.
> Now I want to modify the above pipeline, and insert/delete a  new element
> 'imagefreeze' based on the user input. So the new pipeline looks like this :
> v4l2src -> h264parse -> avdec_h264 -> identity -> imagefreeze -> glupload ->
> glcolorconvert -> gltransformation -> glimagesink.
>
>
> For this I did the following :
> 1. I installed a IDLE probe on source pad of identity.
> 2.  And then in the callback, I unlink identity ->glupload,
> 3. add new element identity and link source pad of identity to sink pad of
> imagefreeze,
> 4.  also  link srcpad of imagefreeze to sink pad of glimagesink.
>
>
> However, I get the following error :
>
>      idsrcpad.link(ifreeze_sinkpad)
>    File "/usr/lib/python3/dist-packages/gi/overrides/Gst.py", line 162, in
> link
>      raise LinkError(ret)
> gi.overrides.Gst.LinkError: <enum GST_PAD_LINK_WRONG_HIERARCHY of type
> Gst.PadLinkReturn>
>
> idsrcpad - the source pad of identity
> ifreeze_sinkpad - the sinkpad of imagefreeze
>
> Here is a snippet from the code:
>
> class Thread
>
>    def __init__(self):
>          thread2 = threading.Thread(target=self.get)
>          thread2.start()
>
>    def get(self):
>          # apply gltransformation
>          # if user input, && set = True, make "drop-probability = 1"
>          identity.set_property("drop-probability",1)
>          idsrcpad = identity.get_static_pad("src")
>          idsrcpad.add_probe (Gst.PadProbeType.IDLE,    self.modify_pipeline)
>        
>        #if user input && set = False, make "drop-probability = 0"
>        ## add code to remove the imagefreeze element, and go back to old
> pipeline.(pending)
>
>    def modify_pipeline(pad,info,self):
>           #1.get sink pad of glupload and unlink identity & glupload
>          upload_sinkpad = upload.get_static_pad("sink")
>          idsrcpad.unlink(upload_sinkpad)
>          #2.get new src and sink pad of imagefreeze
>          ifreeze_sinkpad = ifreeze.get_static_pad("sink")
>          ifreeze_srcpad = ifreeze.get_static_pad("src")
>          #3. link identity src pad to imagefreeze sinkpad
>          idsrcpad = identity.get_static_pad("src")
>          idsrcpad.link(ifreeze_sinkpad)
>          #4. link imagefreeze src pad to upload sink pad
>          ifreeze_srcpad.link(upload_sinkpad)
>
>          return Gst.PadProbeReturn.OK
>
>
> 1. I have tried different ways to solve this issue, but I am unable to find
> a solution. Does anyone know where I am going wrong.
>
> 2. The callback function for add_probe, accepts 2 arguments as per the
> documentation  here
> <https://valadoc.org/gstreamer-1.0/Gst.PadProbeCallback.html>   . However,
> if I define my callback with only 2 arguments (def
> modify_pipeline(pad,info))- I get an error saying the callback accepts only
> 2 arguments, but 3 were provided. The C API of  add_probe
> <https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/GstPad.html#gst-pad-add-probe>
> defines 3 arguments anyhow.
>
> 3. I am also unable to use class members using 'self' inside the callback
> function. Does anyone have some suggestions?
>
>
> Regards.
>
>
>
> --
> Sent from: http://gstreamer-devel.966125.n4.nabble.com/
> _______________________________________________
> gstreamer-devel mailing list
> gstreamer-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>
>