Effect of FEC mechanisms in the performance of low bit rate codecs in lossy mobile environments
Rolando Herrero, Martin Cadirola · 2014
In this paper we focus on Forward Error Correction (FEC) mechanisms based on media redundancy applied to various Low Bit Rate (LBR) speech codecs in the context of lossy mobile environments. Specifically, we deal with different state of the art linear prediction based codecs ranging from narrowband G.729AB and AMR-NB to wideband Opus and SILK, all of them enabled to support Discontinued Transmission (DTX) mode, and packetized over switched networks as RTP/UDP/IP traffic. We evaluate these speech codecs applied in conjunction with media redundancy techniques to a network scenario where packet loss bursts and latency are induced to mimic mobile environments that are normally mathematically modeled as a two-state Markov process. In addition to obtaining the application layer packet loss and comparing it to the mathematical model we also compute the Perceptual Evaluation of Speech Quality (PESQ) score in an attempt to correlate packet loss to real perceived speech quality.