Stereo image quality: Effects of spatio-temporal resolution

We explored the response of the human visual system to mixed-resolution stereo video sequences, in which one eye view was spatially or temporally low-pass filtered. It was expected that perceived quality, stereo depth, and perceived sharpness of sequences would be relatively unaffected by low-pass filtering, compared to the case where both eyes viewed a filtered image. Subjects viewed two 10-second stereo video-sequences, in which the right-eye frames were filtered vertically (V) and horizontally (H) at 1/2H, 1/2V, 1/4H, 1/4V, 1/2H1/2V, 1/2H1/4V, 1/4H1/2V, and 1/4H1/4V resolution. Temporal filtering was implemented for a subset of these conditions at 1/2 temporal resolution, or with dropped-and-repeated frames. Subjects rated the overall quality, sharpness, and overall sensation of depth. It was found that spatial filtering produced acceptable results: The overall sensation of depth was unaffected by low-pass filtering, while ratings of quality and of sharpness were biased towards the eye with the greater spatial resolution. By comparison, temporal filtering produced unacceptable results: Field averaging and dropped-and-repeated frame conditions yielded images with poor quality and sharpness, even though perceived depth was relatively unaffected. We conclude that spatial filtering of one channel of a stereo video-sequence may be an effective means of reducing transmission bandwidth.