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In mixed-resolution (MR) stereoscopic video, one of the views has a lower resolution compared to the other one, hence providing means for improved compression. The underlying assumption in MR stereoscopic video is that the human visual system fuses the left and right views in such a way that the perceived image quality is close to that of the higher-resolution view. This paper describes a subjective quality evaluation experiment with uncompressed MR stereoscopic video, in which the aim was to discover the approximate limit of the downsampling ratio where the perceived quality is still close to the quality of the higher view. Different downsampling ratios, namely 1/2, 3/8, and 1/4 along both coordinate axes, were tested. The threshold of the higher-resolution view being dominant in the perceived quality lied in between downsampling ratios 1/2 and 3/8, corresponding to 11.4 and 7.6 pixels per degree of viewing angle, respectively. At downsampling ratios 3/8 and 1/4, the perceived quality linearly correlated with the average luma peak signal-to-noise ratio of the lower-resolution view.Index Terms -Mixed-resolution stereoscopic video, asymmetric stereoscopic video, binocular suppression

In asymmetric stereoscopic video compression, the views are coded with different qualities. According to the binocular suppression theory, the perceived quality is closer to that of the higher-fidelity view. Hence, a higher compression ratio is potentially achieved through asymmetric coding. Furthermore, when mixed-resolution coding is applied, the complexity of the coding and decoding is reduced. In this paper, we study whether asymmetric stereoscopic video coding achieves the mentioned claimed benefits. Two sets of systematic subjective quality evaluation experiments are presented in the paper. In the first set of the experiments, we analyze the extent of downsampling for the lower-resolution view in mixed-resolution stereoscopic videos. We show that the lower-resolution view becomes dominant in the subjective quality rating at a certain downsampling ratio, and this is dependent on the sequence, the angular resolution, and the angular width. In the second set of the experiments, we compare symmetric stereoscopic video coding, qualityasymmetric stereoscopic video coding, and mixed-resolution coding subjectively. We show that in many cases, mixedresolution coding achieves a similar subjective quality to that

Asymmetric stereoscopic video coding takes advantage of the binocular suppression of the human vision by representing one of the views with a lower quality. This paper describes a subjective quality test with asymmetric stereoscopic video. Different options for achieving compressed mixed-quality and mixed-resolution asymmetric stereo video were studied and compared to symmetric stereo video. The bitstreams for different coding arrangements were simulcast-coded according to the Advanced Video Coding (H.264/AVC) standard. The results showed that in most cases, resolution-asymmetric stereo video with the downsampling ratio of 1/2 along both coordinate axes provided similar quality as symmetric and qualityasymmetric full-resolution stereo video. These results were achieved under same bitrate constrain while the processing complexity decreased considerably. Moreover, in all test cases, the symmetric and mixed-quality full-resolution stereoscopic video bitstreams resulted in a similar quality at the same bitrates.

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