**Ringing**

Ringing is a shimmering effect around high contrast edges. Ringing is not necessarily correlated with blocking as the amount of ringing depends in the amount and strength of edges in the image. A visible ringing measure (VRM) based on the average local variance has been developed in [5]. It is relation to the Gibbs effect.

Marziliano et al. present a ringing metric based on their blur metric describe on previous section, which utilizes the carachteristics from JPEG2000 video encoding to obtain suitable results, but the metric does not extend to other compression standard, but it means a good approximation.
