ffmpeg h265 and banding / blocking artefacts

[marco000]

Hi,

I have tried to compare the result of h265 and h264 codec and while h265 is much better in terms of quality and size reduction, unfortunatenly in my test introduce much banding and block on dark gradient.

Here some commands that I have tried:

(h264)

ffmpeg -y -i title00.mkv  -an  -t 80  -b:v 4M ouput_h264_no_special_options.mkv

This command produce a poor quality result and intruduce grain, but no banding



(h265)

ffmpeg -y -vsync 0   -i title00.mkv  -an -sn -c:v:0 hevc_nvenc  -rc:v:0 vbr  -cq 27 -qmin 22 -qmax 40 -b:v:0 10M -maxrate:v:0 15M -gpu 0 -vf format=yuv420p10le -rc-lookahead 32 -spatial-aq 1 -aq-strength:v 15  -level:v 4.1  -t 80 -tune hq  output_banding.mkv

The quality is much better but introduce banding on dark scene expecially with grey gadient. If I decrease the -cq to 22 the banding persist and seem a bit more evident.

(h265)

ffmpeg -y -i title00.mkv -c:v libx265 -an -aq-mode 3 -aq-strength 16 -deblock -2:-2  -g 120 -keyint_min 120 -t 80  -b:v 4M ouput_h265.mkv

Very very slow with the some banding artefacts no more no less.

My impression is that the h265 have this side effect by default.

If I reduce the gamma the banding is less visible, but the the video is more dark.

I have tried different noise redection via ffmpeg without get good result.

Someone have similar experience about this ?

There is a way to reduce/remove the banding on h265 ?


Thanks !

[Selur]

There is a way to reduce/remove the banding on h265 ?

Use 10bit encoding. The H.265 standard has 10bit encoding in it's main profile which is why all decent hardware decoders support it.

Also:
1. without even sharing the frame size, frame rate there is no chance to judge whether 4Mbit/s might be way too low/high.
2. using 1pass bit rate encoding is usually a bad idea,... 2pass or quality based encoding usually is better.

[marco000]

Thank you.

I have found the solution: using libx265 with this command:

ffmpeg -y  -i title00.mkv  -c:v libx265 -an -crf 23  -x265-params ref=4:hme=1:hme-search=umh,umh,star:subme=4:bframes=8:rd=4:rd-refine=0:qcomp=0.65:fades=1:strong-intra-smoothing=1:ctu=32:qg-size=32:sao=0:selective-sao=0:cu-lossless=0:cutree=1:tu-inter-depth=4:tu-intra-depth=4:max-merge=2:rskip=2:rskip-edge-threshold=2:rc-lookahead=80:aq-mode=1:aq-strength=1.0:rdoq-level=1:psy-rd=4.0:psy-rdoq=15.0:limit-modes=0:limit-refs=0:limit-tu=0:deblock=-4,-4:weightb=1:weightp=1:rect=1:amp=0:wpp=1:pmode=0:pme=0:b-intra=1:b-adapt=2:b-pyramid=1:tskip=1:tskip-fast=0:fast-intra=0:early-skip=0:splitrd-skip=0:min-keyint=24:keyint=240:transfer=bt709:colorprim=bt709:colormatrix=bt709:crf-min=10 -t 80  ouput_h265_forum_very_slow_crf_23.mkv

the final result don't show any banding / blocking but there is a compromise:

with nvidia cuda the process speed is 16x but with this command (libx265) is 0.1X.

After many tests I have undestand that the only way to get a good result is using libx265, but I still looking for a compromise with these paramaters to speedup the process.

My CPU is old Intel I5 6600T and my GPU is GTX 1060.

[www-data]

Hi I tried your settings on live action video , i'm trying to get rid of banding and blocks artefacts from the converted video,
but the the speed was slow ~ 0.2x even after I down scale the video to 1024x576 Is there way to improve speed with less artefacts