DivX265 HEVC Command Line Encoder evaluation

This post details the results of our comparison of the latest version of DivX265 encoder v 1.2, our HEVC command line encoder with HM (HEVC reference encoder), x265 v 0.8 and x264. HEVC test stream BasketballDrive 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 both DivX265 and x265 the fastest and default configurations have been used. For x264 preset veryslow 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, x265 medium, x264 very slow, x265 ultrafast, and finally DivX265 fastest speed. The BD (Bjøntegaard Delta) rate has been calculated between DivX265 and x265 and is 3% when using the default configuration and -14% for the fastest configuration.






Encoding speed

The next plot shows the relative speed of each encoder: DivX265 using the fastest setting encodes this sequence in the shortest amount of time, followed by x265 ultrafast, x264 veryslow, DivX265 balanced, and x265 medium. HM takes the most time to encode this sequence. The fastest settings of DivX265 and x265 are faster than x264 veryslow.

In summary, DivX265 can encode this sequence with better quality than x265 when using the default settings and faster when using the fastest settings.




Encoding settings

Encoder version configuration parameters
HM11 -c ra_main.cfg --IntraPeriod=256 --QP <qp> --FramesToBeEncoded=<frames> ...
DivX2651.2.0.24 -qp <qp> -I 5 -fps 50 -n <frames> [ -aqo 1 | -aqo 3 ] ...
x2650.8+72, 64b --tune psnr --open-gop -i 250 --qp <qp> --fps 50 --frames <frames> [ --preset ultrafast |--preset medium ] ...
x2640.138.2358--preset veryslow --tune psnr --open-gop -I 250 --frames <frames> --qp <qp> --fps 50

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: BasketballDrive_1920x1080_50.yuv, 500 frames, 1920x1080, 50 fps. An encoded copy can be found here: ftp://ftp.kw.bbc.co.uk/hevc/hm-11.0-anchors/bitstreams/ra_main/