How to change frame rate of the stream?

[sonntex]

Input stream has 30 frames per 1 second fps. I want to discard 29 of 30
frames each second. How can I do that?

Pipe looks like:

std::string pipeline =
    "  appsrc name=src0 "
    "! vaapiparse_h264 "
    "! vaapidecode name=decoder0 "
    "! videorate "
    "!   video/x-raw,framerate=1/1 "
    "! videoscale "
    "!   video/x-raw,width=640,height=480 "
    "! vaapiencode_h264 name=encoder0 bitrate=512 keyframe-period=1 "
    "!   video/x-h264,profile=high,stream-format=avc,alignment=au "
    "! vaapiparse_h264 "
    "!   video/x-h264,alignment=nal "
    "! appsink name=sink0";

It makes my video stream slower in 30 times and does not discard frames as
I want.
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