Audio Quality for a Simple Forward Error Correcting Code

The aim of this paper is to study the audio quality offered by a simple Forward Error Correction (FEC) code used in audio applications like Freephone or Rat. This coding technique consists in adding to every audio packet a redundant information concerning a preceding audio packet which belongs to the same audio flow. We show that the audio quality depends not only on the number of FEC flows and the utility function associated to the quantity of information received, but also on the traffic conditions. Indeed, no improvement in the audio quality can be obtained for a smooth traffic whereas a marginal improvement can be observed for a bursty traffic. A significant increase of the audio quality is reached for a heavier bursty traffic. We also show that increasing the offset between the original audio packet and the packet bearing its redundancy does not improve significantly the audio quality.