[asterisk-dev] [Code Review] 4453: Asterisk 14: RTP improvements

Mark Michelson reviewboard at asterisk.org
Fri Feb 27 12:47:58 CST 2015

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Review request for Asterisk Developers.


I've created a series of wiki pages that discuss the idea of writing an improved RTP architecture in Asterisk 14.

To regurgitate some details from the linked page, the current RTP engine in Asterisk (res_rtp_asterisk) gets the job done but has some issues. It is not architected in a way that allows for easy insertion of new features. It has dead code (or code that might as well be dead). And it has some general flaws in it with regards to following rules defined by fundamental RFCs.

I have approached these wiki pages with the idea of writing a replacement for res_rtp_asterisk.c. The reason for this is that there are interesting media-related IETF drafts (trickle ICE and BUNDLE, to name two) that would be difficult to implement in the current res_rtp_asterisk.c code correctly. Taking the opportunity to re-engineer the underlying architecture into something more layered and extendable would help in this regard. The goal also is to not disturb the high-level RTP engine API wherever possible, meaning that channel drivers will not be touched at all by this set of changes.

The main page where this is discussed is here: https://wiki.asterisk.org/wiki/display/AST/RTP+engine+replacement . This page has a subpage that has my informal rambling notes regarding a sampling of RTP and media-related RFCs and drafts I read. It also has a subpage with more informal and rambling notes about the current state of RTP in Asterisk. While these pages are not really part of the review, you may want to read them anyway just so you might have some idea of where I'm coming from when drawing up the ideas behind a new architecture.

I also have a task list page that details a list of high-level tasks that would need to be performed if a new RTP engine were to be written: https://wiki.asterisk.org/wiki/display/AST/RTP+task+list . This should give some idea of the amount of work required to make a new RTP engine a reality. The tasks with (?) around them are tasks that add new features to Asterisk's RTP support, and it is therefore questionable whether they fit in the scope of this work at this time.

Some things to consider when reading through this:
* Refactor or rewrite? When considering current issues with RTP/RTCP in Asterisk, and considering the types of features that are coming down the pipe, which of these options seems more prudent?
* Does the proposed architecture make sense from a high level? Is there confusion about how certain areas are intended to work?
* Are there any glaring details you can think of that have been left out?
* Are there any questions about how specific features would fit into the described architecture?


Diff: https://reviewboard.asterisk.org/r/4453/diff/



Mark Michelson

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