I added a small snippet of the plugin as testtrans.zip zipfile.
In the res-folder is the Cinema4d scene file (crashes) and a json-file.

In the layout res-file I created a simple Baselink, Filename , Button(I want avoid) and BaseTime

Function of the test plugin:

• The user has to drag a pose morph tag into the Baselink.
• Then he has to load the json1.json file as link

The user loads the *.json file (res-folder), I catch this via c4d.MSG_DESCRIPTION_POSTSETPARAMETER and this triggers the function load_transcript() and loads the *.json file content into a member variable self.data.

Questions:

• Main Question: In the Execute(self, tag, doc, op, bt, priority, flags) method I want to to some actions. But here Cinema is crashing. Probably it has something to do with threading and that it asks the tags description.:-).
  I commented out the position where it is crashing. So if I replace the tag[PY_SYNC_START] simply with an integer it works

• Is the method I used in the Message() method correct to detect the changes in the filename link? It doesn't work so I added a button to load it , then it works, but I want it to load as soon as the user changes the link to the json file. It calls the print() function in the POSTSETPARAMETER thing, but it doesn't trigger the load_transfile() method.

• Another small bug maybe in Cinema 4D. When I set the ACCEPT parameter in the Baselink in the res-file to {Tposemorph;} he gives me a ressource error but when I type Tdisplay it works ??????

Here is the code:

import c4d
import os
from c4d import bitmaps, gui, plugins
import json

# be sure to use a unique ID obtained from www.plugincafe.com
PLUGIN_ID = 5554443  # just a test ID

# ID's
PY_MORPH_LINK = 10000
PY_TRANSCRIPT_LINK = 10001
PY_SYNC_START = 10018
PY_LOAD_TRANSCRIPT = 10021


# The Plugin Class
class TestTrans(plugins.TagData):

    def __init__(self):       

        self.data = None

    def Init(self, node):

        self.InitAttr(node, c4d.BaseList2D, PY_MORPH_LINK)
        # node[PY_MORPH_LINK] = None

        self.InitAttr(node, str, PY_TRANSCRIPT_LINK)
        # node[PY_TRANSCRIPT_LINK] = ""

        self.InitAttr(node, c4d.BaseTime, PY_SYNC_START)
        node[PY_SYNC_START] = c4d.BaseTime()

        return True
    
    def load_transcript(self, op):

        if op[PY_TRANSCRIPT_LINK] != "":
            with open(op[PY_TRANSCRIPT_LINK], "r") as transfile:
                self.data = json.load(transfile)

    def move2(self, tag, frame, value):
        print("2. Hello in function")

    def Execute(self, tag, doc, op, bt, priority, flags):

        if self.data:

            pose_morph = tag[PY_MORPH_LINK]

            if not pose_morph:
                return c4d.EXECUTIONRESULT_OK

            morph_count = pose_morph.GetMorphCount()
            print(pose_morph)
            print(self.data["words"])

            frame = doc.GetTime().GetFrame(doc.GetFps()) - tag[PY_SYNC_START]  #Here it is crashing
            print(frame)

            if frame == 10:
                print("1. Hello")

            self.move2(tag, frame, 1)

        return c4d.EXECUTIONRESULT_OK
   

    def Message(self, node, type, data):

        if type == c4d.MSG_DESCRIPTION_COMMAND:

            if data["id"][0].id == PY_LOAD_TRANSCRIPT:
                self.load_transcript(node)

        if type == c4d.MSG_DESCRIPTION_POSTSETPARAMETER:
            if data["descid"][0].id == PY_TRANSCRIPT_LINK:
                print("POSTSETPARAMETER")
                self.load_transcript(node)

        return True


# main
if __name__ == "__main__":
    # load icon.tif from res into bmp
    bmp = bitmaps.BaseBitmap()
    dir, file = os.path.split(__file__)
    fn = os.path.join(dir, "res", "icon.tif")
    bmp.InitWith(fn)

    new_bmp = c4d.bitmaps.InitResourceBitmap(1051133)

    # register the plugin
    c4d.plugins.RegisterTagPlugin(id=PLUGIN_ID,
                                  str="Test-Trans",
                                  info=c4d.TAG_EXPRESSION | c4d.TAG_VISIBLE,
                                  description="testtrans",
                                  g=TestTrans, icon=bmp)

res-file:

CONTAINER Testtrans
{
	NAME TESTTRANS;
	INCLUDE Texpression;

	GROUP ID_TAGPROPERTIES
	{
        LINK PY_MORPH_LINK
        {
            ACCEPT { Tbase; }
        }

        FILENAME PY_TRANSCRIPT_LINK
        {
          ANIM ON;
        }

        BASETIME PY_SYNC_START {}


	}
}

header-file:

#ifndef _TESTTRANS_H_
#define _TESTTRANS_H_
enum
{
    PY_MORPH_LINK           = 10000,
    PY_TRANSCRIPT_LINK      = 10001,
    PY_SYNC_START           = 10018,

	//GV_XPEMIT_NODE_DUMMY
};
#endif // ${FILE_NAME}

string-file:

STRINGTABLE Testtrans // derselbe Name wie res-file
{
	TESTTRANS                       "Test-Trans";
	PY_MORPH_LINK                 "Pose-Morph-Tag";
	PY_TRANSCRIPT_LINK            "Transcript";
       PY_SYNC_START                 "Start";

}

Best Regards
Tom