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

[sk_gst]

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.



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[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
> [hidden email]
> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>
>

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[sk_gst]

Hi Michael,

My main pipeline consists of the following elements and are linked in the
same order:
v4l2src -> h264parse -> avdec_h264 -> identity ->glupload -> glcolorconvert
-> gltransformation -> glimagesink

So when you mean, that element 'imagefreeze' should be a part of the
pipeline- do you mean that I add it to the main pipeline and keep it
unlinked, and based on the event I break the link between identity and
glupload and insert imagefreeze?

Well I always thought that all the elements added to the pipeline must be
linked before, we set the pipeline to playing.

P.S. I have created all the elements before hand, and use them accordingly.



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