A simple script that creates Greasepencil Layers and frames based on a .pg2 project. (Unfinished)

papagayo_import.py

bl_info = {
    "name": "Papagayo-NG 2D Importer",
    "author": "Stefan Murawski", 
    "version": (0, 0, 1),
    "blender": (2, 80, 0),
    "location": "3D window > Tool Shelf",
    "description": "Create GreasePencil Object with Layers and Keyframes from Papagayo-NG .pg2 files.",
    "warning": "",
    "wiki_url": ""
    "Scripts/Import-Export/Papagayo 2D Importer",
    "tracker_url": "",
    "category": "Import-Export"}

import bpy
import json
import os
from bpy_extras.io_utils import ImportHelper 
from bpy.types import Operator, PropertyGroup
from bpy.props import StringProperty, BoolProperty, EnumProperty, PointerProperty

class OT_TestOpenFilebrowser(Operator, ImportHelper): 
    bl_idname = "test.open_filebrowser" 
    bl_label = "Load Papagayo-NG Project" 
    bl_description = 'Load .pg2 or .json files. (Only .pg2 currently)'
    
    filter_glob : StringProperty( default='*.pg2;*.json;', options={'HIDDEN'} )
    
    def execute(self, context): 
        """Do something with the selected file(s).""" 
        filename, extension = os.path.splitext(self.filepath)
        scene = bpy.types.Scene
        scene.pg_path = self.filepath
        return {'FINISHED'}


class BTN_OP_create_grease_objects(Operator):
    bl_idname = 'pg.create_objects'
    bl_label = 'Start Processing'
    bl_description = 'Create Grease Pencil Objects from Papagayo-NG files'

    def execute(self, context):

        scn = context.scene
        obj = context.active_object
        scene = bpy.types.Scene
        create_grease_objects(scene.pg_path)
        scene.pg_objects_created = True
        return {'FINISHED'}
    
class BTN_OP_apply_to_timeline(Operator):
    bl_idname = 'pg.apply_timeline'
    bl_label = 'Start Processing'
    bl_description = 'Create Grease Pencil Objects from Papagayo-NG files'

    def execute(self, context):

        scn = context.scene
        obj = context.active_object
        scene = bpy.types.Scene
        fill_timeline(scene.pg_path)

        return {'FINISHED'}
   
class MyProperties(PropertyGroup):

    rest_frames: BoolProperty(
        name="Enable Rest Frames",
        description="If enabled inserts rest frames into empty frames after words and phrases.",
        default = False
        )
                        
class PapagayoNGImporterUI(bpy.types.Panel):
    bl_id_name = "pg_main_menu"
    bl_space_type = "VIEW_3D"
    bl_region_type = "UI"
    bl_label = "Papagayo-NG 2D Importer"
    bl_category = 'Animation'

    def draw(self, context):

        obj = bpy.context.active_object
        scn = bpy.context.scene
        scene = bpy.types.Scene
        layout = self.layout
        col = layout.column()
        mytool = context.scene.my_tool
        col.prop(mytool, "rest_frames")
        col.operator('test.open_filebrowser', text="Select Papagayo-NG Project File")
        col.separator()
        if scene.pg_path:
            col.label(text=os.path.split(scene.pg_path)[1], icon="FILE_FOLDER")
        else:
            col.label(text="No File loaded", icon="FILE_FOLDER")
        col.separator()
        if scene.pg_path:
            col.label(text="Used Phonemes:")
            for phoneme in get_list_of_phonemes(scene.pg_path):
                col.label(text=phoneme)                
            col.operator("pg.create_objects", text="Create Grease Pencil Objects")
        if scene.pg_objects_created:
            col.separator()
            col.label(text="Add the Grease Pencil Objects to your scene.")
            col.label(text="Simply click on the keyframes to edit them.", icon="KEYFRAME")
            col.label(text="Add sound by choosing Add and the Speaker.")
            col.label(text="Draw all Phonemes and press the next button.")
            col.separator()
            col.operator("pg.apply_timeline", text="Apply to Timeline")

def get_list_of_phonemes(file_path):
    papagayo_file = open(file_path, "r")
    papagayo_json = json.load(papagayo_file)
    list_of_used_phonemes = []
    if file_path.endswith(".pg2"):
        for voice in papagayo_json["voices"]:
            list_of_used_phonemes.append(voice["name"] + ":")
            for phoneme_left, phoneme_right in zip(voice["used_phonemes"][::2], voice["used_phonemes"][1::2]):
                list_of_used_phonemes.append("{}  |  {}".format(phoneme_left, phoneme_right))
    else:
        list_of_used_phonemes.append(papagayo_json["name"] + ":")
        for phoneme_left, phoneme_right in zip(papagayo_json["used_phonemes"][::2], papagayo_json["used_phonemes"][1::2]):
                list_of_used_phonemes.append("{}  |  {}".format(phoneme_left, phoneme_right))
    papagayo_file.close()
    return list_of_used_phonemes
            
def create_grease_objects(file_path):
    papagayo_file = open(file_path, "r")
    papagayo_json = json.load(papagayo_file)
    FPS = papagayo_json["fps"]
    bpy.context.scene.render.fps = FPS
    scene = bpy.types.Scene
    sound_path = ""
    if os.path.isabs(papagayo_json["sound_path"]): 
        sound_path = papagayo_json["sound_path"]
    else:
        sound_path = os.path.join(os.path.dirname(file_path), papagayo_json["sound_path"])
    if not bpy.data.sounds.items():
        bpy.ops.sound.open_mono(filepath=sound_path)
    scene.pg_sound_data = bpy.data.sounds[0]
    prev_area_type = bpy.context.area.type
    bpy.context.area.type = 'SEQUENCE_EDITOR'
    bpy.ops.sequencer.sound_strip_add(filepath=sound_path, frame_start=0, channel=1)
    bpy.context.area.type = prev_area_type
    
    if file_path.endswith(".pg2"):
        # Audio loads fine, can be used with manually added speaker, but this speaker stays silent...
        """
        if not bpy.data.speakers.items():
            bpy.ops.object.speaker_add()

        speaker = bpy.data.speakers[0]
        speaker.sound = scene.pg_sound_data
        """
        NUM_FRAMES = papagayo_json["sound_duration"]
    else:
        NUM_FRAMES = papagayo_json["end_frame"]
    FRAMES_SPACING = 1  # distance between frames
    bpy.context.scene.frame_start = 0
    bpy.context.scene.frame_end = NUM_FRAMES*FRAMES_SPACING
    bpy.context.scene.frame_current = 0
    if file_path.endswith(".pg2"):
        for voice in papagayo_json["voices"]:
            curr_name = voice["name"]
            bpy.ops.object.mode_set(mode = 'OBJECT')
            bpy.ops.object.gpencil_add(align="WORLD", location=(0,0,0), 
                                       scale=(1,1,1), type="EMPTY")                        
            bpy.context.object.name = str(curr_name) + "_stroke"                                   
            if curr_name not in bpy.data.grease_pencils:
                bpy.data.grease_pencils.new(curr_name)
            for phoneme in voice["used_phonemes"]:
                if phoneme not in bpy.data.grease_pencils[curr_name].layers:
                    bpy.data.grease_pencils[curr_name].layers.new(phoneme)
                pho_layer = bpy.data.grease_pencils[curr_name].layers[phoneme]
                try:
                    frame = pho_layer.frames[0]
                except IndexError:
                    pho_layer.frames.new(0)
            bpy.data.objects[curr_name + "_stroke"].data = bpy.data.grease_pencils[curr_name]
    else:
        curr_name = papagayo_json["name"]
        bpy.ops.object.mode_set(mode = 'OBJECT')
        bpy.ops.object.gpencil_add(align="WORLD", location=(0,0,0), 
                                   scale=(1,1,1), type="EMPTY")                        
        bpy.context.object.name = str(curr_name) + "_stroke"   
        if curr_name not in bpy.data.grease_pencils:
            bpy.data.grease_pencils.new(curr_name)
        for phoneme in papagayo_json["used_phonemes"]:
            if phoneme not in bpy.data.grease_pencils[curr_name].layers:
                bpy.data.grease_pencils[curr_name].layers.new(phoneme)
            pho_layer = bpy.data.grease_pencils[curr_name].layers[phoneme]
            try:
                frame = pho_layer.frames[0]
            except IndexError:
                pho_layer.frames.new(0)
        bpy.data.objects[curr_name + "_stroke"].data = bpy.data.grease_pencils[curr_name]
    papagayo_file.close()


def fill_timeline(file_path):
    papagayo_file = open(file_path, "r")
    papagayo_json = json.load(papagayo_file)
    last_pos = 0
    voice_list = []
    if file_path.endswith(".pg2"):
        for voice in papagayo_json["voices"]:
            voice_list.append(voice)
    else:
        voice_list.append(papagayo_json)
    
    for voice in voice_list:
        curr_name = voice["name"]
        if curr_name + "combined" in bpy.data.grease_pencils[curr_name].layers: # TODO: Show a warning and allow to abort
            bpy.data.grease_pencils[curr_name].layers[curr_name + "combined"].clear()
        else:
            bpy.data.grease_pencils[curr_name].layers.new(curr_name + "combined")
        for phrase in voice["phrases"]:
            if bpy.context.scene.my_tool.rest_frames:
                if phrase["start_frame"] > last_pos + 1:
                    base_frame = bpy.data.grease_pencils[curr_name].layers["rest"].frames[0]
                    new_frame = bpy.data.grease_pencils[curr_name].layers[curr_name + "combined"].frames.copy(base_frame)
                    new_frame.frame_number = last_pos + 1
            for word in phrase["words"]:
                if bpy.context.scene.my_tool.rest_frames:
                    if word["start_frame"] > last_pos + 1:
                        base_frame = bpy.data.grease_pencils[curr_name].layers["rest"].frames[0]
                        new_frame = bpy.data.grease_pencils[curr_name].layers[curr_name + "combined"].frames.copy(base_frame)
                        new_frame.frame_number = last_pos + 1
                for phoneme in word["phonemes"]:
                    base_frame = bpy.data.grease_pencils[curr_name].layers[phoneme["text"]].frames[0]
                    new_frame = bpy.data.grease_pencils[curr_name].layers[curr_name + "combined"].frames.copy(base_frame)
                    new_frame.frame_number = phoneme["frame"]
                    last_pos = phoneme["frame"]
            
        """
        if bpy.context.scene.my_tool.rest_frames:
            for frame in range(bpy.context.scene.frame_start, bpy.context.scene.frame_end):
                exists = False
                try:
                    t_frame = bpy.data.grease_pencils[curr_name].layers[curr_name + "combined"].frames[frame]
                    exists = True
                except IndexError:
                    exists = False
                if exists:
                    base_frame = bpy.data.grease_pencils[curr_name].layers["rest"].frames[-1]
                    new_frame = bpy.data.grease_pencils[curr_name].layers[curr_name + "combined"].frames.copy(base_frame)
                    new_frame.frame_number = frame
        """
    papagayo_file.close()
    

def create_keyframes(file_path):
    papagayo_file = open(file_path, "r")
    papagayo_json = json.load(papagayo_file)
    FPS = papagayo_json["fps"]
    bpy.context.scene.render.fps = FPS
    if file_path.endswith(".pg2"):
        NUM_FRAMES = papagayo_json["sound_duration"]
    else: NUM_FRAMES = papagayo_json["end_frame"]
    FRAMES_SPACING = 1  # distance between frames
    bpy.context.scene.frame_start = 0
    bpy.context.scene.frame_end = NUM_FRAMES*FRAMES_SPACING
    voice_list = []
    if file_path.endswith(".pg2"):
        for voice in papagayo_json["voices"]:
            voice_list.append(voice)
    else:
        voice_list.append(papagayo_json)

    for voice in voice_list:
        
        curr_name = voice["name"]
        if curr_name not in bpy.data.grease_pencils:
            bpy.data.grease_pencils.new(curr_name)
        for phrase in voice["phrases"]:
            for word in phrase["words"]:
                for phoneme in word["phonemes"]:
                    if phoneme["text"] not in bpy.data.grease_pencils[curr_name].layers:
                        bpy.data.grease_pencils[curr_name].layers.new(phoneme["text"])
                    try:
                        pho_frame = bpy.data.grease_pencils[curr_name].layers[phoneme["text"]].frames.new(phoneme["frame"])
                    except RuntimeError:
                        pass
        
classes = (PapagayoNGImporterUI, BTN_OP_create_grease_objects, BTN_OP_apply_to_timeline, OT_TestOpenFilebrowser, MyProperties)
                    
def register():
    scene = bpy.types.Scene
    scene.pg_path = ""
    scene.pg_objects_created = False
    for cls in classes:
        bpy.utils.register_class(cls)    
    bpy.types.Scene.my_tool = PointerProperty(type=MyProperties)

def unregister(): 
    for cls in classes:
        bpy.utils.unregister_class(cls)
    del bpy.types.Scene.my_tool
    
if __name__ == "__main__": 
    register()

I updated this script to show the used phonemes.
And I tested this now in Blender 2.93, it actually works as expected.
The Frames are all combined into the combined layer and the playback shows the animation!
If you then add the sound file it will play that together with the animation.
I guess it was a bug of Blender itself before that my frames were empty.

wow. sounds awesome. Let me download and give it a try.

It should now be able to use the .json files from Papagayo-NG besides the .pg2 project files! (untested)

Wow. Looks great. Let me download and give it a try.