Source of HEVC/NAL

- RTP Payload Format for H.265/HEVC Video  -  draft-ietf-payload-rtp-h265-15.txt
--  https://tools.ietf.org/html/draft-ietf-payload-rtp-h265-15#section-1.1.4

- 2.2.2 VCL NAL Unit Types
--  http://what-when-how.com/Tutorial/topic-397pct9eq3/High-Efficiency-Video-Coding-HEVC-29.html