opencv_contrib: cv2.cudacodec.createVideoReader error when input is a video stream

System information (version)

• OpenCV => 4.5.2
• Operating System / Platform => linux
• Compiler => gcc

Detailed description

I built opencv_contrib_python by myself. Here is the build information

Extra dependencies:          m pthread cudart_static dl rt nppc nppial nppicc nppidei nppif nppig nppim nppist nppisu nppitc npps cublas cudnn cufft -L/usr/local/cuda/lib64 -L/lib64
    3rdparty dependencies:

  OpenCV modules:
    To be built:                 calib3d core cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudastereo cudawarping cudev dnn features2d flann highgui imgcodecs imgproc ml objdetect photo python3 stitching video videoio ximgproc
    Disabled:                    aruco bgsegm bioinspired ccalib datasets dnn_objdetect dnn_superres dpm face fuzzy hfs img_hash intensity_transform line_descriptor mcc optflow phase_unwrapping plot quality rapid reg rgbd saliency shape stereo structured_light superres surface_matching text tracking videostab wechat_qrcode world xfeatures2d xobjdetect xphoto
    Disabled by dependency:      cudaoptflow
    Unavailable:                 alphamat cnn_3dobj cvv freetype gapi hdf java julia matlab ovis python2 sfm ts viz
    Applications:                -
    Documentation:               NO
    Non-free algorithms:         NO

  GUI: 
    GTK+:                        NO

  Media I/O: 
    ZLib:                        /usr/local/lib/libz.so (ver 1.2.12)
    JPEG:                        /usr/local/lib/libjpeg.so (ver 90)
    WEBP:                        build (ver encoder: 0x020f)
    PNG:                         /usr/local/lib/libpng.so (ver 1.6.37)
    TIFF:                        build (ver 42 - 4.2.0)
    JPEG 2000:                   build (ver 2.4.0)
    HDR:                         YES
    SUNRASTER:                   YES
    PXM:                         YES
    PFM:                         YES

  Video I/O:
    DC1394:                      NO
    FFMPEG:                      YES
      avcodec:                   YES (58.91.100)
      avformat:                  YES (58.45.100)
      avutil:                    YES (56.51.100)
      swscale:                   YES (5.7.100)
      avresample:                NO
    GStreamer:                   NO
    v4l/v4l2:                    YES (linux/videodev2.h)

  Parallel framework:            pthreads

  Trace:                         YES (with Intel ITT)

  Other third-party libraries:
    VA:                          NO
    Lapack:                      NO
    Eigen:                       NO
    Custom HAL:                  NO
    Protobuf:                    build (3.5.1)

  NVIDIA CUDA:                   YES (ver 11.0, CUFFT CUBLAS NVCUVID)
    NVIDIA GPU arch:             35 37 50 52 60 61 70 75 80
    NVIDIA PTX archs:

  cuDNN:                         YES (ver 8.1.1)

I want to use cuda to accelerate video decoding, but only found it worked on files. I want to use it on video stream.

Steps to reproduce

import cv2
url="rtsp://admin:admin@192.168.2.46/media/video1"

cpu:

cv2.VideoCapture(url).read() # worked

gpu:

cv2.cudacodec.createVideoReader(url).next_frame()

get

opencv_contrib/modules/cudacodec/src/video_reader.cpp:128: error: (-210:Unsupported format or combination of formats) Unsupported video source in function 'nextFrame'

but if the url is a video file both cpu and gpu worked.

Issue submission checklist

• I report the issue, it’s not a question
• I checked the problem with documentation, FAQ, open issues, forum.opencv.org, Stack Overflow, etc and have not found any solution
• I updated to the latest OpenCV version and the issue is still there
• There is reproducer code and related data files: videos, images, onnx, etc