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Sequence Detection

renderkit.core.sequence.SequenceDetector

Detects and parses frame sequences from file patterns.

Source code in src/renderkit/core/sequence.py 
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class SequenceDetector:
    """Detects and parses frame sequences from file patterns."""

    # Common VFX frame number patterns
    PATTERNS = [
        (r"%(\d+)d", "%04d"),  # Houdini style: render.%04d.exr
        (r"\$F(\d+)", "$F4"),  # Houdini style: render.$F4.exr
        (r"(#+)", "####"),  # Maya style: render.####.exr
        (r"(\d+)", "0001"),  # Numeric: render.0001.exr
    ]

    @staticmethod
    def detect_sequence(pattern: str) -> FrameSequence:
        """Detect a frame sequence from a pattern string.

        Supports patterns like:
        - render.%04d.exr (Houdini)
        - render.$F4.exr (Houdini)
        - render.####.exr (Maya)
        - render.0001.exr (numeric)

        Args:
            pattern: File pattern with frame number placeholder

        Returns:
            FrameSequence object

        Raises:
            SequenceDetectionError: If sequence cannot be detected
        """
        pattern_path = Path(pattern)
        base_path = pattern_path.parent
        filename = pattern_path.name

        # Try to detect which pattern is being used
        detected_pattern = None
        padding = 4
        frame_numbers: list[int] = []

        # Check for %04d pattern
        if "%" in filename and "d" in filename:
            match = re.search(r"%(\d+)d", filename)
            if match:
                padding = int(match.group(1))
                detected_pattern = filename
                # Find all matching files
                frame_numbers = SequenceDetector._find_frames_by_pattern(
                    base_path, filename, padding, "%04d"
                )

        # Check for $F4 pattern
        elif "$F" in filename:
            match = re.search(r"\$F(\d+)", filename)
            if match:
                padding = int(match.group(1))
                detected_pattern = filename
                frame_numbers = SequenceDetector._find_frames_by_pattern(
                    base_path, filename, padding, "$F4"
                )

        # Check for #### pattern
        elif "#" in filename:
            match = re.search(r"(#+)", filename)
            if match:
                padding = len(match.group(1))
                detected_pattern = filename
                frame_numbers = SequenceDetector._find_frames_by_pattern(
                    base_path, filename, padding, "####"
                )

        # Check for numeric pattern (e.g., render.0001.exr)
        else:
            numeric_match = re.search(r"(\d+)", filename)
            if numeric_match:
                # Try to find sequence by replacing the number
                frame_numbers = SequenceDetector._find_frames_by_numeric_pattern(
                    base_path, filename, numeric_match
                )
                if frame_numbers:
                    padding = len(numeric_match.group(1))
                    detected_pattern = filename

        if not frame_numbers:
            raise SequenceDetectionError("Could not detect frame sequence.")

        return FrameSequence(base_path, detected_pattern or filename, frame_numbers, padding)

    @staticmethod
    def _find_frames_by_pattern(
        base_path: Path, pattern: str, padding: int, placeholder: str
    ) -> list[int]:
        """Find frame numbers matching a pattern.

        Args:
            base_path: Directory to search
            pattern: Pattern string with placeholder
            padding: Number of digits for padding
            placeholder: The placeholder string to replace

        Returns:
            List of frame numbers found
        """
        frame_numbers: list[int] = []
        pattern_regex = pattern

        # Convert pattern to regex
        if placeholder == "%04d":
            pattern_regex = re.sub(r"%\d+d", lambda m: r"(\d+)", pattern)
        elif placeholder == "$F4":
            pattern_regex = re.sub(r"\$F\d+", lambda m: r"(\d+)", pattern)
        elif placeholder == "####":
            pattern_regex = re.sub(r"#+", lambda m: r"(\d+)", pattern)

        regex = re.compile(pattern_regex)

        # Search for matching files
        if base_path.exists():
            for file_path in base_path.iterdir():
                if file_path.is_file():
                    match = regex.match(file_path.name)
                    if match:
                        try:
                            frame_num = int(match.group(1))
                            frame_numbers.append(frame_num)
                        except (ValueError, IndexError):
                            continue

        return sorted(frame_numbers)

    @staticmethod
    def _find_frames_by_numeric_pattern(
        base_path: Path, filename: str, numeric_match: re.Match[str]
    ) -> list[int]:
        """Find frame numbers by replacing numeric part of filename.

        Args:
            base_path: Directory to search
            filename: Filename with numeric pattern
            numeric_match: Regex match object for the numeric part

        Returns:
            List of frame numbers found
        """
        frame_numbers: list[int] = []
        start_pos, end_pos = numeric_match.span()
        prefix = filename[:start_pos]
        suffix = filename[end_pos:]

        # Try to find files with same prefix/suffix but different numbers
        if base_path.exists():
            pattern_regex = re.compile(re.escape(prefix) + r"(\d+)" + re.escape(suffix))
            for file_path in base_path.iterdir():
                if file_path.is_file():
                    match = pattern_regex.match(file_path.name)
                    if match:
                        try:
                            frame_num = int(match.group(1))
                            frame_numbers.append(frame_num)
                        except ValueError:
                            continue

        return sorted(frame_numbers)

    @staticmethod
    def auto_detect_fps(
        frame_numbers: list[int],
        default_fps: Optional[float] = None,
        sample_path: Optional[Path] = None,
    ) -> Optional[float]:
        """Auto-detect frame rate from frame numbers or metadata.

        Args:
            frame_numbers: List of frame numbers
            default_fps: Default FPS to return if detection fails
            sample_path: Optional path to a file in the sequence to check for metadata

        Returns:
            Detected FPS or default, or None if cannot determine
        """
        # 1. Try metadata first if a sample path (e.g. first frame) is provided
        if sample_path and sample_path.exists():
            try:
                from renderkit.io.image_reader import ImageReaderFactory
                from renderkit.io.oiio_cache import get_shared_image_cache

                reader = ImageReaderFactory.create_reader(
                    sample_path, image_cache=get_shared_image_cache()
                )
                fps = reader.get_metadata_fps(sample_path)
                if fps is not None:
                    return round(fps, 3)  # Round to avoid precision issues (e.g. 23.976)
            except Exception:
                # Silently fail for metadata detection
                pass

        # 2. Return default or None
        return default_fps

auto_detect_fps(frame_numbers, default_fps=None, sample_path=None) staticmethod

Auto-detect frame rate from frame numbers or metadata.

Parameters:

Name Type Description Default
frame_numbers list[int]

List of frame numbers

 required
default_fps Optional[float]

Default FPS to return if detection fails

 None
sample_path Optional[Path]

Optional path to a file in the sequence to check for metadata

 None

Returns:

Type Description
Optional[float]

Detected FPS or default, or None if cannot determine
Source code in src/renderkit/core/sequence.py 
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@staticmethod
def auto_detect_fps(
    frame_numbers: list[int],
    default_fps: Optional[float] = None,
    sample_path: Optional[Path] = None,
) -> Optional[float]:
    """Auto-detect frame rate from frame numbers or metadata.

    Args:
        frame_numbers: List of frame numbers
        default_fps: Default FPS to return if detection fails
        sample_path: Optional path to a file in the sequence to check for metadata

    Returns:
        Detected FPS or default, or None if cannot determine
    """
    # 1. Try metadata first if a sample path (e.g. first frame) is provided
    if sample_path and sample_path.exists():
        try:
            from renderkit.io.image_reader import ImageReaderFactory
            from renderkit.io.oiio_cache import get_shared_image_cache

            reader = ImageReaderFactory.create_reader(
                sample_path, image_cache=get_shared_image_cache()
            )
            fps = reader.get_metadata_fps(sample_path)
            if fps is not None:
                return round(fps, 3)  # Round to avoid precision issues (e.g. 23.976)
        except Exception:
            # Silently fail for metadata detection
            pass

    # 2. Return default or None
    return default_fps

detect_sequence(pattern) staticmethod

Detect a frame sequence from a pattern string.

Supports patterns like: - render.%04d.exr (Houdini) - render.$F4.exr (Houdini) - render.####.exr (Maya) - render.0001.exr (numeric)

Parameters:

Name Type Description Default
pattern str

File pattern with frame number placeholder

 required

Returns:

Type Description
FrameSequence

FrameSequence object

Raises:

Type Description
SequenceDetectionError

If sequence cannot be detected
Source code in src/renderkit/core/sequence.py 
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@staticmethod
def detect_sequence(pattern: str) -> FrameSequence:
    """Detect a frame sequence from a pattern string.

    Supports patterns like:
    - render.%04d.exr (Houdini)
    - render.$F4.exr (Houdini)
    - render.####.exr (Maya)
    - render.0001.exr (numeric)

    Args:
        pattern: File pattern with frame number placeholder

    Returns:
        FrameSequence object

    Raises:
        SequenceDetectionError: If sequence cannot be detected
    """
    pattern_path = Path(pattern)
    base_path = pattern_path.parent
    filename = pattern_path.name

    # Try to detect which pattern is being used
    detected_pattern = None
    padding = 4
    frame_numbers: list[int] = []

    # Check for %04d pattern
    if "%" in filename and "d" in filename:
        match = re.search(r"%(\d+)d", filename)
        if match:
            padding = int(match.group(1))
            detected_pattern = filename
            # Find all matching files
            frame_numbers = SequenceDetector._find_frames_by_pattern(
                base_path, filename, padding, "%04d"
            )

    # Check for $F4 pattern
    elif "$F" in filename:
        match = re.search(r"\$F(\d+)", filename)
        if match:
            padding = int(match.group(1))
            detected_pattern = filename
            frame_numbers = SequenceDetector._find_frames_by_pattern(
                base_path, filename, padding, "$F4"
            )

    # Check for #### pattern
    elif "#" in filename:
        match = re.search(r"(#+)", filename)
        if match:
            padding = len(match.group(1))
            detected_pattern = filename
            frame_numbers = SequenceDetector._find_frames_by_pattern(
                base_path, filename, padding, "####"
            )

    # Check for numeric pattern (e.g., render.0001.exr)
    else:
        numeric_match = re.search(r"(\d+)", filename)
        if numeric_match:
            # Try to find sequence by replacing the number
            frame_numbers = SequenceDetector._find_frames_by_numeric_pattern(
                base_path, filename, numeric_match
            )
            if frame_numbers:
                padding = len(numeric_match.group(1))
                detected_pattern = filename

    if not frame_numbers:
        raise SequenceDetectionError("Could not detect frame sequence.")

    return FrameSequence(base_path, detected_pattern or filename, frame_numbers, padding)