processing_hyperclovax.py

import copy
import os
import re
import uuid
from typing import Dict, List, Optional, Union

import numpy as np
import PIL
from PIL import Image
import torch
from transformers.feature_extraction_utils import BatchFeature
from transformers.image_utils import ImageInput
from transformers.processing_utils import (
    AllKwargsForChatTemplate,
    ChatTemplateLoadKwargs,
    ProcessingKwargs,
    ProcessorMixin,
    TextInput,
    Unpack,
    VideoInput,
)
from transformers.tokenization_utils_base import AudioInput
from transformers.utils import (
    is_torch_device,
    is_torch_dtype,
    logging,
    requires_backends,
)
from transformers.video_utils import VideoInput, VideoMetadata, load_video

logger = logging.get_logger(__name__)


class HCXBatchFeature(BatchFeature):
    def to(self, *args, **kwargs) -> "BatchFeature":
        """
        Send all values to device by calling `v.to(*args, **kwargs)` (PyTorch only). This should support casting in
        different `dtypes` and sending the `BatchFeature` to a different `device`.

        Args:
            args (`Tuple`):
                Will be passed to the `to(...)` function of the tensors.
            kwargs (`Dict`, *optional*):
                Will be passed to the `to(...)` function of the tensors.
                To enable asynchronous data transfer, set the `non_blocking` flag in `kwargs` (defaults to `False`).

        Returns:
            [`BatchFeature`]: The same instance after modification.
        """
        requires_backends(self, ["torch"])
        import torch  # noqa

        new_data = {}
        device = kwargs.get("device")
        non_blocking = kwargs.get("non_blocking", False)
        # Check if the args are a device or a dtype
        if device is None and len(args) > 0:
            # device should be always the first argument
            arg = args[0]
            if is_torch_dtype(arg):
                # The first argument is a dtype
                pass
            elif isinstance(arg, str) or is_torch_device(arg) or isinstance(arg, int):
                device = arg
            else:
                # it's something else
                raise ValueError(f"Attempting to cast a BatchFeature to type {str(arg)}. This is not supported.")
        # We cast only floating point tensors to avoid issues with tokenizers casting `LongTensor` to `FloatTensor`
        for k, v in self.items():
            # check if v is a floating point
            if isinstance(v, torch.Tensor) and torch.is_floating_point(v):
                # cast and send to device
                new_data[k] = v.to(*args, **kwargs)
            elif isinstance(v, torch.Tensor) and device is not None:
                new_data[k] = v.to(device=device, non_blocking=non_blocking)
            elif "pixel_values" in k:
                new_pixel_values_batch = []
                for _v in v:
                    pixel_values = [pixel_value.to(device=device, non_blocking=non_blocking) for pixel_value in _v]
                    new_pixel_values_batch.append(pixel_values)
                new_data[k] = new_pixel_values_batch
            else:
                new_data[k] = v
        self.data = new_data
        return self


class HCXProcessorKwargs(ProcessingKwargs, total=False):
    _defaults = {
        "text_kwargs": {
            "return_tensors": "pt",
            "calc_non_vision_query_lengths": False,
        },
        "images_kwargs": {},
        "audio_kwargs": {},
        "videos_kwargs": {
            "max_image_cnt": 12,
            "max_num_grids": 9,
        },
    }


class HCXProcessor(ProcessorMixin):
    attributes = ["image_processor", "tokenizer"]
    valid_kwargs = ["chat_template"]

    image_processor_class = "AutoImageProcessor"
    tokenizer_class = ("GPT2Tokenizer", "GPT2TokenizerFast")

    def __init__(self, image_processor=None, tokenizer=None, chat_template=None, **kwargs):
        self.image_token = "<|dummy3|>"
        self.video_token = "<|_unuse_missing_100270|>"
        self.image_token_pattern = re.compile(r"<\|dummy3\|>")
        self.video_token_pattern = re.compile(r"<\|_unuse_missing_100270\|>")
        self.image_video_token_pattern = re.compile(r"<\|dummy3\|>|<\|_unuse_missing_100270\|>")
        self.image_token_id = (
            tokenizer.image_token_id
            if getattr(tokenizer, "image_token_id", None)
            else tokenizer.convert_tokens_to_ids(self.image_token)
        )
        self.video_token_id = (
            tokenizer.video_token_id
            if getattr(tokenizer, "video_token_id", None)
            else tokenizer.convert_tokens_to_ids(self.video_token)
        )
        super().__init__(image_processor, tokenizer, chat_template=chat_template)

    def apply_chat_template(
        self,
        conversation: Union[list[dict[str, str]], list[list[dict[str, str]]]],
        chat_template: Optional[str] = None,
        **kwargs: Unpack[AllKwargsForChatTemplate],
    ) -> str:
        model_inputs = super().apply_chat_template(conversation, chat_template, **kwargs)

        # vllm needs vision_query_lengths, but we don't need it
        del model_inputs["vision_query_lengths_images"]
        del model_inputs["vision_query_lengths_videos"]

        # # vllm 호환성을 위해 이곳에서 token 을 vision_query_length만큼 늘리기 처리
        # if "input_ids" in model_inputs:
        #     # self.image_token 모두 찾기
        #     input_ids = self.repeat_dummy_tokens(
        #         model_inputs["input_ids"], self.image_token_id, model_inputs["vision_query_lengths_images"]
        #     )
        #     input_ids = self.repeat_dummy_tokens(
        #         input_ids, self.video_token_id, model_inputs["vision_query_lengths_videos"]
        #     )
        #     model_inputs["input_ids"] = input_ids
            
        return model_inputs
    
    def repeat_dummy_tokens(self, input_ids, target_token_id, vision_query_lengths):
        input_ids = input_ids.clone().detach()
        batch_indices, target_indices = torch.where(input_ids == target_token_id)
        batch_size = input_ids.shape[0]

        new_input_ids = [[] for _ in range(batch_size)]
        start_indices = [0 for _ in range(batch_size)]
        counter = [0 for _ in range(batch_size)]
        for batch_idx, target_idx in zip(batch_indices, target_indices):
            start_idx = start_indices[batch_idx]
            new_input_ids[batch_idx].append(input_ids[batch_idx][start_idx:target_idx])
            query_length = vision_query_lengths[batch_idx][counter[batch_idx]]
            new_input_ids[batch_idx].append(input_ids[batch_idx][target_idx].repeat(query_length))
            start_indices[batch_idx] = target_idx + 1
            counter[batch_idx] += 1

        for batch_idx in range(batch_size):
            start_idx = start_indices[batch_idx]
            new_input_ids[batch_idx].append(input_ids[batch_idx][start_idx:])  # append remaining tokens
            new_input_ids[batch_idx] = torch.cat(new_input_ids[batch_idx], dim=0)

        new_input_ids = torch.stack(new_input_ids)
        return new_input_ids

    def _load_video_for_model(
        self,
        video: str,
        num_frames: Optional[int] = None,
        fps: Optional[int] = None,
        backend: str = "opencv",
        **kwargs: Unpack[HCXProcessorKwargs],
    ) -> List[ImageInput]:
        """
        Overrided function.

        Loads `video` to a List[PIL.Image] (llava style)

        Args:
            video (`str`):
                The video to convert to the numpy array format. Can be a link to video or local path.
            num_frames (`int`, *optional*):
                Number of frames to sample uniformly. If not passed, the whole video is loaded.
            fps (`int`, *optional*):
                Number of frames to sample per second. Should be passed only when `num_frames=None`.
                If not specified and `num_frames==None`, all frames are sampled.
            backend (`str`, *optional*, defaults to `"opencv"`):
                The backend to use when loading the video. Can be any of ["decord", "pyav", "opencv", "torchvision"]. Defaults to "opencv".

        Returns:
            Tuple[`np.array`, Dict]: A tuple containing:
                - List[PIL.Image] of frames in RGB.
                - Metadata dictionary.
        """
        output_kwargs = self._merge_kwargs(
            HCXProcessorKwargs,
            tokenizer_init_kwargs=self.tokenizer.init_kwargs,
            **kwargs,
        )

        logger.warning_once(f"num_frames control via argument is not supported yet. Ignored num_frames: {num_frames}.")
        logger.warning_once(f"fps control via argument is not supported yet. Ignored fps: {fps}.")
        logger.warning_once(f"backend control via argument is not supported yet. Ignored backend: {backend}.")

        def _hcx_sample_indices_fn(metadata: VideoMetadata, num_frames=None, fps=None, **kwargs):
            max_num_grids = output_kwargs["videos_kwargs"]["max_num_grids"]
            max_image_cnt = output_kwargs["videos_kwargs"]["max_image_cnt"]
            frame_indices, time_interval = extract_frame_indices(
                metadata.duration,
                metadata.total_num_frames,
                metadata.fps,
                max_num_grids,
                max_image_cnt,
                default_interval=0.4,
            )
            metadata.time_interval = time_interval
            return np.array(frame_indices)

        video_loaded, video_metadata = None, None
        for backend in ["decord", "pyav", "opencv", "torchvision"]:
            try:
                video_loaded, video_metadata = load_video(
                    video, sample_indices_fn=_hcx_sample_indices_fn, backend=backend
                )
                break
            except Exception as e:
                logger.error(f"Error loading video with {backend} backend: {e}")
                continue

        assert video_loaded is not None, "Failed to load video with any backend"

        return video_loaded, video_metadata

    def _process_messages_for_chat_template(
        self,
        conversation: List[List[Dict[str, str]]],
        batch_images: List[List[ImageInput]],
        batch_videos: List[List[VideoInput]],
        batch_video_metadata: List[List[Dict[str, any]]],
        **mm_load_kwargs: Unpack[ChatTemplateLoadKwargs],
    ):
        """
        Overrided function.
        Used within `apply_chat_template` when a model has a special way to process conversation history. For example,
        video models might want to specify in the prompt the duration of video or which frame indices at which timestamps
        were sampled. This information cannot be accessed before the video is loaded.

        For most models it is a no-op, and must be overridden by model processors which require special processing.

        Args:
            conversation (`List[Dict, str, str]`):
                The conversation to process. Always comes in batched format.
            batch_images (`List[List[ImageInput]]`):
                Batch of images that were loaded from url/path defined in the conversation. The images
                are ordered in the same way as in the conversation. Comes in nested list format, one list of `PIL` images
                per batch.
            batch_videos (`List[List[ImageInput]]`):
                Batch of videos that were loaded from url/path defined in the conversation. The videos
                are ordered in the same way as in the conversation. Comes in nested list format, one list of `PIL.Image`
                per batch.
            batch_video_metadata (`List[List[Dict[[str, any]]]]`):
                Batch of metadata returned from loading videos. That includes video fps, duration and total number of framer in original video.
                Metadata are ordered in the same way as `batch_videos`. Comes in nested list format, one list of `Dict`
                per batch.
        """

        is_video_in_conversation = False
        for batch_idx, messages in enumerate(conversation):
            is_video_in_messages = False
            is_image_in_messages = False
            for message in messages:
                for content in message["content"]:
                    if content["type"] == "video":
                        is_video_in_messages = True
                    elif content["type"] == "image":
                        is_image_in_messages = True
            if not is_video_in_messages:
                batch_videos.insert(batch_idx, [])
                batch_video_metadata.insert(batch_idx, [])
            if not is_image_in_messages:
                batch_images.insert(batch_idx, [])

            is_video_in_conversation = is_video_in_conversation or is_video_in_messages

        if not is_video_in_conversation:
            return conversation

        # conversation processing
        new_conversation = []
        for batch_idx, messages in enumerate(conversation):
            video_counter = 0
            new_messages = []

            for message in messages:
                new_message = {
                    "role": message["role"],
                    "content": [],
                }
                for content in message["content"]:
                    if content["type"] == "video":
                        video = batch_videos[batch_idx][video_counter]
                        video_meta = batch_video_metadata[batch_idx][video_counter]

                        time_stamps = calc_timestamp_video_grids(video, video_meta.time_interval, max_grid_shape=(3, 3))
                        video_counter += 1

                        if "filename" in content:
                            filename = content["filename"]
                        else:
                            filename = content["video"].split("/")[-1]
                            if len(filename) > 50:
                                filename = f"{uuid.uuid4().hex}.mp4"
                        basename, ext = os.path.splitext(filename)
                        if ext == "":
                            ext = ".mp4"

                        for frame_idx, time_stamp in enumerate(time_stamps):
                            if frame_idx == len(video) - 1:
                                # final_grid
                                new_content = {
                                    "filename": f"{basename}-{frame_idx}{ext}",
                                    "video": content["video"],
                                    "type": "video",
                                    "video_time_stamp": time_stamp,
                                    "lens_keywords": content["lens_keywords"],
                                    "lens_local_keywords": content["lens_local_keywords"],
                                    "speech_to_text": content["speech_to_text"],
                                    "is_final_grid": True,
                                }
                                new_message["content"].append(new_content)
                            else:
                                new_content = {
                                    "filename": f"{basename}-{frame_idx}{ext}",
                                    "video": content["video"],
                                    "type": "video",
                                    "video_time_stamp": time_stamp,
                                }
                                new_message["content"].append(new_content)
                    else:
                        new_message["content"].append(copy.deepcopy(content))
                new_messages.append(new_message)
            new_conversation.append(new_messages)

        return new_conversation

    def __call__(
        self,
        text: TextInput = None,
        images: List[List[ImageInput]] = None,
        videos: List[List[VideoInput]] = None,
        audio: AudioInput = None,
        **kwargs: Unpack[HCXProcessorKwargs],
    ):
        output_kwargs = self._merge_kwargs(
            HCXProcessorKwargs,
            tokenizer_init_kwargs=self.tokenizer.init_kwargs,
            **kwargs,
        )

        # prepare model inputs
        mm_inputs = {
            "pixel_values_images": [],
            "image_sizes_images": [],
            "vision_query_lengths_images": [],
            "pixel_values_videos": [],
            # "image_sizes_videos": [],
            "vision_query_lengths_videos": [],
        }
        calc_non_vision_query_lengths = output_kwargs["text_kwargs"].pop("calc_non_vision_query_lengths")
        if calc_non_vision_query_lengths:
            mm_inputs["non_vision_query_lengths"] = []

        # video processing
        if videos is not None:
            vit_input_size = self.image_processor.crop_size["width"]

            video_kwargs = copy.deepcopy(output_kwargs["videos_kwargs"])

            for videos_in_single_conversation in videos:
                pixel_values_videos = []
                vision_query_lengths_videos = []

                for video_frames in videos_in_single_conversation:
                    if len(video_frames) == 0:
                        mm_inputs["pixel_values_videos"].append([])
                        mm_inputs["vision_query_lengths_videos"].append([])
                        continue
                    video_frames_combined = combine_frames_into_images(
                        video_frames, max_grid_shape=(3, 3), vit_input_size=vit_input_size
                    )
                    video_kwargs["is_video"] = True
                    video_kwargs["return_tensors"] = None

                    frames_processed = self.image_processor(images=video_frames_combined, **video_kwargs)
                    sizes = [(size["width"], size["height"]) for size in frames_processed["image_sizes"]]

                    pixel_values_videos.extend(frames_processed["pixel_values"])
                    vision_query_lengths_videos.extend(frames_processed["vision_query_lengths"])

                mm_inputs["pixel_values_videos"].append(pixel_values_videos)
                mm_inputs["vision_query_lengths_videos"].append(vision_query_lengths_videos)

        # image processing
        if images is not None:
            image_kwargs = copy.deepcopy(output_kwargs["images_kwargs"])
            image_kwargs["is_video"] = False
            image_kwargs["return_tensors"] = None

            for images_in_single_conversation in images:
                if isinstance(images_in_single_conversation, PIL.Image.Image): # single item to batch
                    images_in_single_conversation = [images_in_single_conversation, ]
                if len(images_in_single_conversation) == 0:
                    mm_inputs["pixel_values_images"].append([])
                    mm_inputs["image_sizes_images"].append([])
                    mm_inputs["vision_query_lengths_images"].append([])
                    continue
                images_processed = self.image_processor(images=images_in_single_conversation, **image_kwargs)
                sizes = [(size["width"], size["height"]) for size in images_processed["image_sizes"]]

                mm_inputs["pixel_values_images"].append(images_processed["pixel_values"])
                mm_inputs["image_sizes_images"].append(sizes)
                mm_inputs["vision_query_lengths_images"].append(images_processed["vision_query_lengths"])

        # text processing
        def _create_replacer(_target_token, _replacements):
            _iterator = iter(_replacements)

            def _replacer(match_obj):
                # return self.image_token
                num_query_tokens = next(_iterator)
                return "".join(
                    [_target_token for _ in range(num_query_tokens)]
                )  # vision_query_legnth 만큼 image token 을 복제

            return _replacer

        text_inputs = {}
        if text is not None:
            if not isinstance(text, list):
                text = [text]

            if images is not None:
                new_texts = []
                for batch_idx, text_in_single_conversation in enumerate(text):
                    new_text = self.image_token_pattern.sub(
                        _create_replacer(self.image_token, mm_inputs["vision_query_lengths_images"][batch_idx]),
                        text_in_single_conversation,
                    )
                    new_texts.append(new_text)
                text = new_texts

            if videos is not None:
                new_texts = []
                for batch_idx, text_in_single_conversation in enumerate(text):
                    new_text = self.video_token_pattern.sub(
                        _create_replacer(self.video_token, mm_inputs["vision_query_lengths_videos"][batch_idx]),
                        text_in_single_conversation,
                    )
                    new_texts.append(new_text)
                text = new_texts

            text_inputs = self.tokenizer(text, **output_kwargs["text_kwargs"])

        # audio processing
        if audio is not None:
            raise NotImplementedError("Audio processing is not supported yet.")

        return HCXBatchFeature(data={**text_inputs, **mm_inputs})

    def decode(self, *args, **kwargs):
        """
        This method forwards all its arguments to Siglip2Tokenizer's [`~PreTrainedTokenizer.decode`]. Please refer to
        the docstring of this method for more information.
        """
        return self.tokenizer.decode(*args, **kwargs)

    def batch_decode(self, *args, **kwargs):
        """
        This method forwards all its arguments to Siglip2Tokenizer's [`~PreTrainedTokenizer.batch_decode`]. Please
        refer to the docstring of this method for more information.
        """
        return self.tokenizer.batch_decode(*args, **kwargs)

    def post_process_image_text_to_text(
        self, generated_outputs, skip_special_tokens=True, clean_up_tokenization_spaces=False, **kwargs
    ):
        """
        Post-process the output of the model to decode the text.

        Args:
            generated_outputs (`torch.Tensor` or `np.ndarray`):
                The output of the model `generate` function. The output is expected to be a tensor of shape `(batch_size, sequence_length)`
                or `(sequence_length,)`.
            skip_special_tokens (`bool`, *optional*, defaults to `True`):
                Whether or not to remove special tokens in the output. Argument passed to the tokenizer's `batch_decode` method.
            Clean_up_tokenization_spaces (`bool`, *optional*, defaults to `False`):
                Whether or not to clean up the tokenization spaces. Argument passed to the tokenizer's `batch_decode` method.
            **kwargs:
                Additional arguments to be passed to the tokenizer's `batch_decode method`.

        Returns:
            `List[str]`: The decoded text.
        """
        return self.tokenizer.batch_decode(
            generated_outputs,
            skip_special_tokens=skip_special_tokens,
            clean_up_tokenization_spaces=clean_up_tokenization_spaces,
            **kwargs,
        )

    @property
    def model_input_names(self):
        tokenizer_input_names = self.tokenizer.model_input_names
        image_processor_input_names = self.image_processor.model_input_names
        names_from_processor = list(dict.fromkeys(tokenizer_input_names + image_processor_input_names))
        return names_from_processor + []


def extract_frame_indices(play_time, total_frames, fps, max_num_grids, max_image_cnt, default_interval=0.4):
    """
    Extracts specific frame indices from a video based on duration, frame count, and sampling strategy.

    The function determines which frames to extract given the video duration (`play_time`),
    total frame count, and frame rate. It samples frames at regular intervals (default: 0.4s),
    but if the number of frames exceeds the limit defined by `max_num_grids * max_image_cnt`,
    it performs uniform sampling to stay within that limit.

    Args:
        play_time (float): Total play time of the video in seconds.
        total_frames (int): Total number of frames in the video.
        fps (float): Frames per second of the video.
        max_num_grids (int): Maximum number of grids to display.
        max_image_cnt (int): Maximum number of images per grid.
        default_interval (float, optional): Interval in seconds between frame samples. Defaults to 0.4.

    Returns:
        Tuple:
            frame_indices (List[int]): A list of selected frame indices.
            time_interval (float): Time interval between selected frames (in seconds).
    """

    # Calculate how many frames to extract with the default interval
    default_frame_count = int(play_time / default_interval)

    # Maximum frames allowed based on max_num_grids and max_image_cnt
    max_frames_allowed = max_num_grids * max_image_cnt

    # Determine whether we can use the default interval or need uniform sampling
    if default_frame_count <= max_frames_allowed:
        # Default interval is sufficient, extract frames every 0.4 seconds
        frame_interval = int(total_frames / default_frame_count)
    else:
        # Use uniform sampling to fit within max_frames_allowed
        frame_interval = int(total_frames / max_frames_allowed)

    # Extract frame indices at the calculated interval
    selected_indices = list(range(0, total_frames, frame_interval))

    time_interval = frame_interval / fps

    # Ensure the number of selected indices does not exceed max_frames_allowed
    return selected_indices[:max_frames_allowed], time_interval


def calc_timestamp_video_grids(frames, time_interval, max_grid_shape=(3, 3)):
    """
    Calculates the time range labels for each grid in a video.

    Args:
        frames (List[PIL.Image.Image]): A list of frames extracted from a video.
        time_interval (float): Time interval (in seconds) between consecutive frames.
        max_grid_shape (Tuple[int, int], optional): The maximum grid shape as (rows, cols). Defaults to (3, 3).
        vit_input_size (int, optional): The target size (height and width) for the Vision Transformer input. Defaults to 378.

    Returns:
        Tuple:
            image_time_stamps (List[str]): A list of time span labels for each combined image,
                e.g., ["0.00s~1.50s", "1.50s~3.00s", ...].
    """
    max_num_grids = max_grid_shape[0] * max_grid_shape[1]
    # assert (
    #     max_grid_shape[1] == 1
    # ), f"For video processing, decided to concatenate frames horizontally into a wide image."

    # Calculate the number of canvases needed.
    num_frames = len(frames)
    num_canvases = num_frames // max_num_grids
    leftover_frames = num_frames % max_num_grids

    time_stamp = 0  # second
    image_time_stamps = []

    for canvas_idx in range(num_canvases):
        # Determine the frames to fill in the current canvas.
        start_idx = canvas_idx * max_num_grids
        end_idx = min(start_idx + max_num_grids, num_frames)

        # Append the current canvas to the result list.
        frame_cnt = end_idx - start_idx
        image_time_stamps.append(f"{time_stamp:.2f}s~{time_stamp + frame_cnt * time_interval:.2f}s")
        time_stamp += frame_cnt * time_interval

    if leftover_frames > 0:
        # Add the current canvas to the list of combined images.
        frame_cnt = leftover_frames
        image_time_stamps.append(f"{time_stamp:.2f}s~{time_stamp + frame_cnt * time_interval:.2f}s")
        time_stamp += frame_cnt * time_interval

    return image_time_stamps


def combine_frames_into_images(frames, max_grid_shape=(3, 3), vit_input_size=378):
    """
    Combines a sequence of video frames into grid-based images and generates corresponding time range labels.

    Frames are grouped and arranged into a grid (e.g., 3x3) such that each combined image contains up to
    `max_grid_shape[0] * max_grid_shape[1]` frames. Each combined image is resized to the given ViT input size.

    Args:
        frames (NDArray): (num_frames, H, W, C) shape. A list of frames extracted from a video.
        time_interval (float): Time interval (in seconds) between consecutive frames.
        max_grid_shape (Tuple[int, int], optional): The maximum grid shape as (rows, cols). Defaults to (3, 3).
        vit_input_size (int, optional): The target size (height and width) for the Vision Transformer input. Defaults to 378.

    Returns:
        Tuple:
            image_list (List[PIL.Image.Image]): A list of grid-combined images.
    """
    max_num_grids = max_grid_shape[0] * max_grid_shape[1]
    # assert (
    #     max_grid_shape[1] == 1
    # ), f"For video processing, decided to concatenate frames horizontally into a wide image."

    # List to store the resulting combined images.
    image_list = []

    # Calculate the number of canvases needed.
    num_frames = len(frames)
    num_canvases = num_frames // max_num_grids
    leftover_frames = num_frames % max_num_grids

    # change frames (4d numpy tensor) to List[PIL.Image.Image]
    frames = [Image.fromarray(frame) for frame in frames]

    for canvas_idx in range(num_canvases):
        # Initialize the current canvas.
        combined_image = Image.new(
            "RGB", (vit_input_size * max_grid_shape[0], vit_input_size * max_grid_shape[1]), color=(0, 0, 0)
        )

        # Determine the frames to fill in the current canvas.
        start_idx = canvas_idx * max_num_grids
        end_idx = min(start_idx + max_num_grids, num_frames)

        for idx in range(start_idx, end_idx):
            img = frames[idx]

            # Resize each frame to a square shape.
            img_resized = img.resize((vit_input_size, vit_input_size))

            # Calculate the (row, column) position to place the frame within the grid layout.
            local_idx = idx - start_idx
            x_offset = (local_idx % max_grid_shape[0]) * vit_input_size
            y_offset = (local_idx // max_grid_shape[0]) * vit_input_size

            # Calculate the position to place the frame in the grid.
            combined_image.paste(img_resized, (x_offset, y_offset))

        # Append the current canvas to the result list.
        image_list.append(combined_image)

    if leftover_frames > 0:
        # canvas_idx might be undefined; default to 0 if not previously assigned to avoid "referenced before assignment" error.
        canvas_idx = num_canvases
        # Add the remaining frames to the final canvas.
        # combined_image = Image.new("RGB", (vit_input_size * leftover_frames, vit_input_size * 1), color=(0, 0, 0))  # hsk
        combined_image = Image.new(
            "RGB", (vit_input_size * max_grid_shape[0], vit_input_size * max_grid_shape[1]), color=(0, 0, 0)
        )

        for idx in range(leftover_frames):
            img = frames[num_canvases * max_num_grids + idx]

            # Resize the frame to a square (equal width and height).
            img_resized = img.resize((vit_input_size, vit_input_size))

            # Calculate the (row, column) position to place the frame within the grid layout.
            # x_offset = (idx % leftover_frames) * vit_input_size  # hsk
            # y_offset = (idx // leftover_frames) * vit_input_size  # hsk
            x_offset = (idx % max_grid_shape[0]) * vit_input_size
            y_offset = (idx // max_grid_shape[0]) * vit_input_size

            # Calculate the position to place the frame within the grid layout.
            combined_image.paste(img_resized, (x_offset, y_offset))

        # Add the current canvas to the list of combined images.
        image_list.append(combined_image)

    return image_list