RTSP Frame Buffer Value for DVB C Streaming with FritzBox

[Apple-M1]

Following Problem with M1 using VLC.

Problem:
Using DVB-C Stream from Cable Fritzbox with a given RTSP Playlist. The Stream has latency problems some Dropouts and other Picture Problems during playing.

Testing to solve:
Tried all thing with buffering in related sections but without any success.

And here is a Problem to adjusting the RTSP Frame Buffer Size the Standard Value is shown with 250.000, trying to switch in any other value does not work. After changing the Video is not playing again it stand still to much more time to show something.

Would be nice to get a hint if it possible to change in any other way the Size of Frame Buffer. If I Could change I Hope with a greater Buffer Size to get a better Stream without Dropouts or things like this.

Thanks for help.