Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion.

Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules.


Go Back   Doom9's Forum > Video Encoding > High Efficiency Video Coding (HEVC)

Thread Tools Search this Thread Display Modes
Prev Previous Post   Next Post Next
Old 1st June 2021, 13:44   #1  |  Link
Registered User
Join Date: May 2021
Posts: 4
Problem about rate control of x265

I use x265 to encode a 720p video with crf+vbv.
The commond as below:
./x265 --input wz_720p.yuv --preset medium --input-res 1280x720 --vbv-maxrate 1400 --vbv-bufsize 2000 --aq-mode 1 --rc-lookahead 16 --keyint 90 --bframes 3 --crf 24 --frame-threads 8 --fps 30 --psnr -o wz_720p.265

I chang the crf from 24 to 30,and I found something strange,when the bitrate achives the maxrate,the lower crf will case lower psnr.
24 1459.5768 40.8106
25 1456.7784 40.7936
26 1456.7792 40.7553
27 1457.0216 40.9836
28 1390.7492 40.9035
29 1233.576 40.2643
30 1093.8648 39.6247
From the result above,we can found the psnr of crf27 is bigger than crf26 while they have similar bitrate.
I have test other seqences,all have this phenomenon. The R-PSNR curve is not monotonic increasing,it will decrease when the bitrate exceeds the maxrate.
I want to know how to solve this problem,when the bitrate achives the maxrate how to make the psnr and bitrate not change with the crf decrease.
hanyi is offline   Reply With Quote

rate control, x265

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT +1. The time now is 03:27.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.