Constant RTP_VERSION_HEADER_BITS 

const RTP_VERSION_HEADER_BITS: u8 = _; // 128u8

RTP version bits in the first octet of RTP and RTCP packets.

References:

• https://www.rfc-editor.org/rfc/rfc3550.html#section-5.1
• https://www.rfc-editor.org/rfc/rfc3550.html#section-6.4.1