By Peter Deierlein and Aravanan Gurusami, Philips Broadband Networks Inc.
With the industry wide adaptation of the Ghost Canceling Reference (GCR), commercial products for high quality video ghost cancellation have become practical for the cable operators at their headend. However, co-channel interference accounts for as much as one third of all reception problems. Further, both impulse and random noise related picture impairments are a concern for quality conscious operators. With the cost of high speed digital signal processing becoming more affordable, innovative and powerful real time processing techniques can now be applied for enhancing picture quality.
While mathematical modelling of co-channel interference is at its conceptual stage, it is well known that the primary impact on the picture degradation is related to carrier beat and horizontal line frequency harmonics. Significant improvement of co-channel interference impairments can be handled by addressing these problems.
Expensive studio quality products are available today for the reduction of both impulse and random noise impairment. These devices employ a combination of frame storage, impairment detection, and impairment concealment using substitution and/or averaging techniques.
With the progress being made in digital video compression and HDTV many of these techniques can be re-examined with the economy of the cable operators in mind. This paper examines the status of the technical community in these challenging areas.