DivX265 HEVC Command Line Encoder evaluation

This post details the results of our comparison of the latest version of DivX265 encoder v 1.5, our HEVC command line encoder with HM (HEVC reference encoder), x265 v 1.6 and x264. HEVC test stream Kimono1 has been encoded using QP values {22,27,32,37}. The DivX HEVC profile limits the keyframe interval. For this evaluation we have set the keyframe interval to 5 seconds for each encoding. For DivX265 and x265 configurations have been used that result in approx similar encoding speed and reasonalble quality (Balanced) For x264 preset slow has been used.

Encoding efficiency

The encoding efficiency can be derived from the rate-distortion plot. HM achieves the highest encoding efficiency, followed by DivX265 (balanced, main10), DivX265 (balanced) thereafter x265 (preset fast, main10), x265 (preset fast) and finally x264 (preset slow). The BD (Bjøntegaard Delta) rate has been calculated between DivX265 and x265 and is approx 5.6%. I.e. the DivX265 encoded stream is 5.6% smaller for the same quality.




Encoding speed

The next plot shows the relative speed of each encoder: DivX265 (balanced, main) is faster (~1.3x) than x265 (fast, main) at this preset while, as shown in the plot above, it is also 5.6% more efficient.

In summary, DivX265 can encode this sequence faster and more efficient than x265 at these settings. The encoding speed is approx 16 fps for balanced and faster than real-time, up to 40 fps, for the faster modes while the quality is better than x264 (AVC) for a given speed on this 4/8 core machine.




Encoding settings

Encoder version configuration parameters
HM11 -c ra_main.cfg --IntraPeriod=120 --QP <qp> --FramesToBeEncoded=<frames> ...
DivX2651.5 64b -qp <qp> -I 5 -fps 24 -n <frames> -aqo 3 ...
DivX265 (10b)1.5 64b -qp <qp> -I 5 -fps 24 -n <frames> -aqo 3 --main10 ...
x2651.6+185, 64b, 8bpp --tune psnr --open-gop -I 120 --qp <qp> --fps 24 --frames <frames> --preset fast ...
x265 (10b)1.6+185, 64b, 16bpp --tune psnr --open-gop -I 120 --qp <qp> --fps 24 --frames <frames> --preset fast ...
x2640.138.2358--preset slow --tune psnr --open-gop -I 120 --frames <frames> --qp <qp> --fps 24

Notes

DivX265 will create DivX HEVC profiles compliant streams. The exact profile is determined by the resolution and frame rate. For example 1920x1080@50 will select the 4K profile limits and allows therefore for a much higher bitrate than for example 1920x1080@30. The latter will use the 1080HD profile limits.

Other

Encoding speed measured on a PC with W7-SP1-64, i7-3820QM@2.7GHz, 16GB

Sequence properties: Kimono1_1920x1080_24.yuv, 240 frames, 1920x1080, 24 fps. An encoded copy can be found here: ftp://ftp.kw.bbc.co.uk/hevc/hm-11.0-anchors/bitstreams/ra_main/