any help for this error

[saitarunk]

ubuntu 20.04

Workstation:~/Desktop/YOLOv4-Pytorch$ python3 detect.py -input ./file.mp4 --video -output ./det.avi
Parsing config into model...
Parsing class names...
Loading weights...

Could not find encoder for codec id 27: Encoder not found
[ERROR:0] global /io/opencv/modules/videoio/src/cap.cpp (415) open VIDEOIO(CV_IMAGES): raised OpenCV exception:

OpenCV(4.2.0) /io/opencv/modules/videoio/src/cap_images.cpp:253: error: (-5:Bad argument) CAP_IMAGES: can't find starting number (in the name of file): ./det.avi in function 'icvExtractPattern'