It is demonstrated that H.265 achieves equivalent image quality at half the bit rate of H.264

H.264 (MPEG-4 AVC)Of the successor standard "H.265 (HEVC)Is a standard that is said to be able to achieve image quality equivalent to that of H.264 at half bit rate and is expected to be used for ultra high resolution images such as 8K and streaming applications for mobile terminals. A demonstration experiment by IEEE researchers was conducted on H.265, and the result that it is now possible to realize the same image quality with twice the compression rate has been issued.

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H.265 / HEVC vs H.264 / AVC: 50% bit rate savings verified - BBC R & D
http://www.bbc.co.uk/rd/blog/2016/01/h-dot-265-slash-hevc-vs-h-dot-264-slash-avc-50-percent-bit-rate-savings-verified

H.265 boasts a high compression ratio twice as high as H.264, and it is already possible to maintain the same image quality in a state where the bit rate has been greatly suppressed for H.264 (data capacity is small)PSNR (peak signal-to-noise ratio)It was demonstrated using. PSNR is a criterion for calculating the degradation degree of compressed (encoded) video from calculation, so the high compression ratio of H.265 was proved as "objective evaluation".

In our experiments, it was found that H.265 has a higher compression ratio than H.264 for "subjective evaluation" to have a human encoded video and judge the beauty of the video by sensation It is verified whether it is.

Experiments were conducted with four different resolutions of 4 K (3840 × 2160, 4096 × 2048), 1080 p (1920 × 1080), 720 p (1280 × 720), and 480 p (832 × 480), frames different from 30 Hz, 50 Hz, By comparing the compressed video encoded by H.265 and H.264 in comparison with the original video, we compared the compressed video encoded by H.265 and H.264 with the setting of the rate, and compared with the original video, the high reproducibility (less deterioration) To judge to.


The experimental method is to first evaluate the original video in the first 10 seconds, see the compressed video encoded for 1 second, and evaluate the reproducibility of the video in 10 steps. H We are examining the compression ratio of .265 and H.264 standards.


The result is as follows. In the graph, the horizontal axis represents the bit rate (Mbps) of the video, and the vertical axis represents the subjective evaluation (MOS) · PSNR (dB). The result of PSNR which is an objective evaluation is indicated by a broken line, the graph is shifted to the left compared with H.264 of black (▲) for H.265 of black (●), the lower bit rate You can see that equivalent image quality can be obtained with. As indicated by the solid line, the subjective evaluation MOS is shifted to the left as compared with H.264 of red () H.265, blue (▲), similar to objective evaluation It is clear that high image quality is obtained at a lower bit rate.


According to the research team, the wide range of coding block sizes and the ability to use many coding modes using prediction algorithms supports the high compression ratio of H.265. In the experiment, the bit rate that can be reduced to obtain the same image quality was about 44% in the objective evaluation PSNR, whereas in the subjective evaluation MOS, about 59%, the subjective experiment Concluded that it was able to suppress the bit rate considerably, and the beauty of the video encoded in H.265 seems to be able to experience more than the data measurement value.