Open Standards for secure communications abound. sRTP is baked into many voip hardware phones. High end Cisco SPA525g2 comes to mind readily.
[decryption and inspection] would cause a significant delay with a resulting decrease in the quality of the communications. Encoded audio and video is difficult to impossible to determine if an attack is being perpetrated or if sensitive information is being improperly disclosed without reconstituting the analog audio and video signals and having a person listen and watch each communication. Due to the volume of communications, to do so would be nearly impossible. — STIG V-19671
Crank up the volume people!
OpenConnect, a free interoperable alternative to Cisco AnyConnect VPN
Sagaciou.s * H.imself