Improving the Efficiency of Video Coding by using
Perceptual Preprocessing Filter
Rahul Vanam and Yuriy A. Reznik,
InterDigital Communications, LLC, 9710 Scranton Road, San Diego, CA 92121 USA
We propose design of a pre-processing filter that improves effectiveness of video coding
by removing spatial oscillations that are invisible under given viewing conditions, such as
display contrast, pixel density, and a distance between user and the screen. Figure 1
shows an exemplary deployment of a mobile video delivery system using such a filter.
Viewing distance, display
density, contrast ratio
Figure 1: Video delivery system utilizing perceptual pre-processing filter.
The block-diagram of our proposed filter is shown in Figure 2.
[C]xy = [A]xy /
[Fc]xy = F(Cxy)
Figure 2: Block diagram of our perceptual filter.
The underlying phenomenon exploited by our filter is known as Contrast Sensitivity
Function (CSF) of human vision . We use Movshon and Kiorpes CSF model .
In order to apply it, we extract luminance channel, adjust black level to account contrast
of the screen, and then compute local averages and amplitudes of oscillations in the span
of about 2o of viewing angle. We then compute local contrasts of oscillations and then use the
CSF model to estimate highest visible frequency in such regions. We use such frequencies to
control a low-pass filter applied to an image.
In our experiments with 4.3”, 720p-resolution screens, held at distances in 12–24” range,
and ambient light of 0–2000 lux, we have observed savings of up to 70% of bitrate.
We have used H.264 video codec and standard video test sequences in our tests.
 A. C. Bovik, “Handbook of image and video processing”. Academic Press, 2005.
 J. Movshon and L. Kiorpes, “Analysis of the development of spatial contrast sensitivity in monkey and
human infants,” JOSA A, vol. 5, no. 12, pp. 2166–2172, 1988.
2013 Data Compression Conference
1068-0314/13 $26.00 © 2013 IEEE