Perceptual evaluation of JPEG-coded stereoscopic images

JPEG compression of the left and right components of a stereo image pair is a way to save valuable bandwidth when transmitting stereoscopic images. This paper presents results on the effects of camera-base distance and JPEG-coding on overall image quality, perceived depth, perceived sharpness and perceived eye-strain. In the experiment, two stereoscopic still scenes were used, varying in depth (three different camera-base distances: 0, 8 and 12 cm) and compression ratio (4 levels: original, 1:30, 1:40 and 1:60). All levels of compression were applied to both the left and right stereo image, resulting in a 4x4 matrix of all possible symmetric and asymmetric coding combinations. We applied the single stimulus method for subjective testing according to the ITU 500-10 recommendations. The observers were asked to assess image quality, sharpness, depth and eye-strain. Results showed that JPEG coding had a negative effect on image quality, sharpness and eye-strain but had no effect on perceived depth. An increase in camera-base distance increased perceived depth and reported eye-strain but had no effect on perceived sharpness. Furthermore, both sharpness and eye-strain correlated highly with perceived image quality.