Video reader

class expert.data.video_reader.Cache(capacity: int)[source]

Bases: object

Caching class for decoding videos.

If the same video frame is cached and used a second time, there is no need to decode it twice.

Parameters: capacity (int) – Buffer size for storing frames.
Raises: ValueError – If “capacity” is not a positive integer.

class expert.data.video_reader.VideoReader(filename: Optional[Union[str, os.PathLike]], cache_capacity: Optional[int] = 10)[source]

Bases: object

Class for decoding video to a list object.

This video wrapper class decodes the video and provides access to frames.

Parameters

filename (str | PathLike) – Path to local video file.
cache_capacity (int, optional) – Buffer size for storing frames. Defaults to 10.

Raises

IndexError – If the entered frame index is outside the allowed range of integer values.
IndexError – If the entered frame index is out of range.
StopIteration – If the end of the video has been reached.

property vcap: cv2.VideoCapture

Get VideoCapture object.

Returns: Raw VideoCapture object.
Return type: cv2.VideoCapture

property opened: bool

Check whether the video is opened.

Returns: Indicate whether the video is opened.
Return type: bool

property width: int

Get width of video frames.

Returns: Width of video frames.
Return type: int

property height: int

Get height of video frames.

Returns: Height of video frames.
Return type: int

property resolution: Tuple[int, int]

Get Video resolution (width, height).

Returns: Video resolution (width, height).
Return type: Tuple

property fps: float

Get FPS of the video.

Returns: FPS of the video.
Return type: float

property frame_cnt: int

Get total number frames.

Returns: Total frames of the video.
Return type: int

property fourcc: str

Get four character code.

Returns: “Four character code” of the video.
Return type: str

property position: int

Get current cursor position.

Returns: Current cursor position, indicating frame decoded.
Return type: int

read() → Optional[numpy.ndarray][source]

Read the next frame.

If the next frame have been decoded before and in the cache, then return it directly, otherwise decode, cache and return it.

Returns: Returns the frame if successful, otherwise returns None.
Return type: ndarray or None

get_frame(frame_id: int) → Optional[numpy.ndarray][source]

Get frame by index.

Parameters: frame_id (int) – Index of the expected frame, 0-based.
Returns: Returns the frame if successful, otherwise returns None.
Return type: ndarray or None

current_frame() → Optional[numpy.ndarray][source]

Get the current frame (the frame is just visited).

Returns: If the video is fresh returns None, otherwise returns the frame.
Return type: ndarray or None