Rtsp issue while streaming using opencv

i have tried streaming a lot of rtsp camera links using opencv, for some rtsp links im getting blank grey image as visuals, which in vlc media player is working fine. The information I’m getting from opencv is
[hevc @ 0x133ca80] PPS id out of range: 0
[hevc @ 0x134c040] Could not find ref with POC 22

and for some other cameras im getting status as false when calling cv2.VideoCapture(rtsp).read() with no error message, and also this is working fine in vlc