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Improving the Efficiency of Video Coding by using Perceptual Preprocessing Filter
Research Paper / Feb 2014

 

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 

 

E-mail:{rahul.vanam, yuriy.reznik}@interdigital.com 

 

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. 

 

DecoderEncoder

 

Perceptual

preprocessing

 

filter

 

Sensors

 

Display

 

Viewing distance, display 

density, contrast ratio

 

Network

 

Figure 1: Video delivery system utilizing perceptual pre-processing filter.

 

The block-diagram of our proposed filter is shown in Figure 2.

 

Input video/

image

 

Output

video/image

 

-

+

 

-

 

Viewing

distance

 

Display pixel 

density

 

Contrast ratio

 

Convert to 

linear color 

 

space

 

Extract

Luminance

 

Black-level

adjustment

 

Compute

local DCs:

 

[DC]xy

 

Compute

amplitudes:

 

[A]xy

 

Estimate local 

contrasts:

 

[C]xy = [A]xy /

[DC]xy

 

Estimate cut-off 

frequencies:

 

[Fc]xy = F(Cxy)

 

Convert to 

original color 

 

space

 

Adaptive low-

pass filter

 

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 [1]. We use Movshon and Kiorpes CSF model [2]. 

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. 

 

References

[1] A. C. Bovik, “Handbook of image and video processing”. Academic Press, 2005.

[2] 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

DOI 10.1109/DCC.2013.103

 

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