Video Reader

class apps.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 apps.expert.data.video_reader.VideoReader(filename: str | PathLike, cache_capacity: 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: 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() → np.ndarray | None[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) → np.ndarray | None[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() → np.ndarray | None[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