An evaluation of H.265 or HEVC video compression has demonstrated 50% bit-rate savings over the established H.264 or AVC standard. The results confirm that the newer standard provides a substantial improvement in compression efficiency relative to its predecessor. The study also suggests greater gains when assessed by viewers, compared to a widely used objective measurement.
The evaluation was based on frame sizes up to ultra-high-definition at up to 60 frames per second. The tests involved assessment by viewers in controlled conditions as well as objective measures of comparative quality.
The tests showed that bit rate savings of 59% on average can be achieved by HEVC for the same perceived video quality, which is higher than a bit rate saving of 44% demonstrated using a standard objective quality metric.
The peak-signal-to-noise ratio or PSNR is often used to represent video coding performance, although it does not necessarily account for how images are actually perceived.
For subjective evaluation, a mean opinion score or MOS method was used to represent the scores of a panel of viewers on a scale of 0 to 10.
The evaluation suggests that for a given bit rate the subjective quality improvements of HEVC are typically greater than the objective quality improvements measured by the PSNR method that was mainly used during development of the standard.
The bit-rate savings were also higher for larger picture sizes. However, there was some variation across the sample sequences tested, which are not necessarily representative of the full range of television and video output.
The tests, which were performed in February and March 2014, appear in a journal published in January 2016. BBC Research and Development staff contributed to the paper.
The results suggest that there is a significant gain in compression efficiency with H.265. This remains to be demonstrated in real deployments but it would allow video to be delivered at up to half the data rates that are widely employed. That could be important for delivering ultra-high-definition video.
“Video Quality Evaluation Methodology and Verification Testing of HEVC Compression Performance” appears in IEEE Transactions On Circuits And Systems For Video Technology, January 2016.