This paper presents a study comparing the coding efficiency performance of three software codecs: (a) the HEVC Main
Profile Reference Software; (b) the x265 codec; and (c) VP10. Note here that we are specifically testing only 8-bit
performance. Performance is tabulated for 1-pass encoding on two fronts: (1) objective performance (PSNR), (2)
informal subjective assessment. Finally, two approaches to coding were used: (i) constant quality; and (ii) fixed bit rate.
Constant quality encoding is performed with all the three codecs for an unbiased comparison of the core coding tools.
Whereas target bitrate coding is done to study the compression efficiency achieved with rate control, which can and does
have a significant impact. Our general conclusion is that under constant quality coding, the HEVC reference software
appears to be superior to the other two, whereas with rate control and fixed rate coding, these codecs are more on an
equal footing. We remark that this latter result may be partly or mainly due to the maturity of the various rate control
mechanisms in these codecs.
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