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Showing posts from June, 2013

Redundant RTP coding

There are different mechanisms to make media transmission more robust to packet loss.   Some of those techniques are negative acknowledgments and retransmissions, sending redundant information for forward error correction and signal processing algorithms to reduce the impact of packet looses.

In case of audio codecs with the advent of OPUS most of packet lost issues disappear due to the robustness of the codec.  You can test yourself the quality with 30% of packet loss!!! [1]

Where those techniques makes more sense are with video codecs because they are typically more fragile to packet loss and this is specially critical when sending key frames that can impact communication for a long period of time (until next keyframe).

This post is an overview on how redundant encoding works at RTP level and what are the implications of it.

The core idea is to modify RTP packets format so that instead of including only the primary content payload (video encoded content) it can also include extra b…