Bitrate is too large

[Dillon14281118]

Why the bitrate of svt-hevc is so large compared with x265? I use CQP mode with qp={22,27,32,37} in svt-hevc and x265,the commands are as below: ./SvtHevcEncApp -i ../sc_desktop_1920x1080_60_8bit_420.yuv -w 1920 -h 1080 -n 90 -rc 0 -q 37 -fps 15 -b out.h265

./x265 --input ../sc_desktop_1920x1080_60_8bit_420.yuv --frames 90 --input-res 1920x1080 --input-csp 1 --fps 15 --psnr --tune psnr --qp 37 -o out.h265

use ffmpeg to calc psnr: ./ffmpeg -r 15 -i out.h265 -s:v 1920x1080 -c:v rawvideo -pix_fmt yuv420p -r 15 -i ../sc_desktop_1920x1080_60_8bit_420.yuv -frames 90 -lavfi psnr="stats_file=psnr.log" -f null -

The BD-Rate result is as below(x265 is anchor):

We can found in the result that the bitrate of svt-hevc is about twice that of x265 at the same level psnr. Why the bitrate of svt-hevc is so high? How should I adjust the parameters?

[tianjunwork]

Hey @Dillon14281118 , thanks providing the data. Encoders have their own ways to fine tune trade-off between speed and coding efficiency. It is meaningless to compare BD-rate between different trade-off configs(usually called preset). With default preset of x265 being medium and SVT-HEVC being -encMode 7, according to below preset mapping between x265 and SVT-HEVC, trade-off configs are not at the same level. https://x265.readthedocs.io/en/default/svthevc.html#preset-option-mapping

FYI, link below shows the comparison of AV1/HEVC encoders. https://www.compression.ru/video/codec_comparison/hevc_2019/

[Dillon14281118]

So the result in svt-hevc is normal? Because the psnr is a little low when bitrate is less than 2000k, I want to make sure if the result is normal.

[tianjunwork]

The PSNR curve is steadily decreasing for both SVT-HEVC and X265, from which I didn't see a warning sign.

[tianjunwork]

Hi @Dillon14281118 , anything to discuss further in this issue?