VideoReader¶

class mmcv.video.VideoReader(filename, cache_capacity=10)[source]¶

Video class with similar usage to a list object.

This video wrapper class provides convenient apis to access frames. There exists an issue of OpenCV’s VideoCapture class that jumping to a certain frame may be inaccurate. It is fixed in this class by checking the position after jumping each time. Cache is used when decoding videos. So if the same frame is visited for the second time, there is no need to decode again if it is stored in the cache.

Examples

>>> import mmcv
>>> v = mmcv.VideoReader('sample.mp4')
>>> len(v)  # get the total frame number with `len()`
120
>>> for img in v:  # v is iterable
>>>     mmcv.imshow(img)
>>> v[5]  # get the 6th frame

current_frame()[source]¶

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

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

cvt2frames(frame_dir, file_start=0, filename_tmpl='{:06d}.jpg', start=0, max_num=0, show_progress=True)[source]¶

Convert a video to frame images.

Parameters:

frame_dir (str) – Output directory to store all the frame images.
file_start (int) – Filenames will start from the specified number.
filename_tmpl (str) – Filename template with the index as the placeholder.
start (int) – The starting frame index.
max_num (int) – Maximum number of frames to be written.
show_progress (bool) – Whether to show a progress bar.

property fourcc¶

“Four character code” of the video.

Type:: str

property fps¶

FPS of the video.

Type:: float

property frame_cnt¶

Total frames of the video.

Type:: int

get_frame(frame_id)[source]¶

Get frame by index.

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

property height¶

Height of video frames.

Type:: int

property opened¶

Indicate whether the video is opened.

Type:: bool

property position¶

Current cursor position, indicating frame decoded.

Type:: int

read()[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:: Return the frame if successful, otherwise None.
Return type:: ndarray or None

property resolution¶

Video resolution (width, height).

Type:: tuple

property vcap¶

The raw VideoCapture object.

Type:: cv2.VideoCapture

property width¶

Width of video frames.

Type:: int