Subject: [payload] tx-mode in H.265 RTP draft

From: "Mo Zanaty (mzanaty)" <[email-masked]>
Date: Fri, 6 Mar 2015 03:09:30 +0000

Hi,
Based on implementation experience with tx-mode in draft-ietf-payload-rtp-h265-07, here are some suggested changes in the draft to simplify implementations and SDP as well as avoid PT exhaustion.

tx-mode (Transmission Mode)

The tx-mode parameter is a symmetric configuration point that can be SRST, MRST or MRMT. If multiple are supported, each must be declared in a separate payload type, causing combinatorial explosion of tx-mode, profile, 4 other configuration point parameters, simulcast streams, etc. It is better if the offer can declare support for multiple tx-mode values (comma separated) in the same payload type, and the answer can select a (single) symmetric configuration point.

For example, offer both SRST and MRST:
a=fmtp:96 tx-mode=SRST,MRST; ...

Answer selects MRST:
a=fmtp:96 tx-mode=MRST; ...

This is a very simple extension of the ABNF and SDP O/A rules with modest text changes. It would require review by the SDP Directorate.

If there is agreement on this suggested change, I will propose specific text changes.

Regards,
Mo