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 > Announcements and Chat > General Discussion

Reply
 
Thread Tools Search this Thread Display Modes
Old 8th December 2017, 07:36   #1  |  Link
varekai
Registered User
 
varekai's Avatar
 
Join Date: Jul 2006
Posts: 410
Ultra-HD downscale to 1080p?

Hello,

Is there a way to encode/recode/compress an Ultra-HD to 1080p BD or to 1080p mkv without getting washed out colors?
Done a few tests and I always get very pale colors.
I'm shure there is an explantions to this but I can't figure it out.
Is it even possible to downscale to 1080p and get "normal" full BD colors?
varekai is offline   Reply With Quote
Old 8th December 2017, 08:46   #2  |  Link
Asmodian
Registered User
 
Join Date: Feb 2002
Location: San Jose, California
Posts: 3,539
You probably need to do a color space conversion to BT.709. Most UHD content is encoded as either BT.709 or BT.2020 and if it was BT.709 colors would look correct.

The reason colors look pale is because BT.2020 is a very wide color space, 50% red in BT.2020 is much redder than 50% red in BT.709. Without doing a conversion all the BT.2020 color values are simply displayed as if they were BT.709 color values.

Another option is to tag your encodes as BT.2020, for x264 and assuming an SDR source this might be:
--colorprim bt2020 --transfer bt2020-10 --colormatrix bt2020nc

I have no idea how to do a HDR -> SDR conversion.
__________________
madVR options explained
Asmodian is offline   Reply With Quote
Old 8th December 2017, 09:37   #3  |  Link
Sparktank
47.952fps@71.928Hz
 
Sparktank's Avatar
 
Join Date: Mar 2011
Posts: 895
for HDR -> SDR you can use FFMPEG's internal tone-mapping.
https://ffmpeg.org/ffmpeg-filters.html#tonemap
You'll have test various parts to ensure that different scenes don't look too out of place (light vs dark vs natural light vs etc).

It also looks pale if it's HDR content, which will need to be converted to SDR (via FFMPEG).

You could encode to HEVC in 1080p and keep the HDR metadata to passthru and let MadVR convert to SDR (this limits to PC playback only).

There's a vapoursynth script somewhere here to convert HDR -> SDR. Not sure how well it works compared to FFMPEG conversions.
https://forum.doom9.org/showthread.php?t=174415

Those are the only automatic processes that are free and easily accessible.
__________________
Win10 (x64) build 17134 | GPU Caps Viewer 1.40.1.0
NVIDIA GeForce GT 1030 (GP108) 2047MB/GDDR5 | (R417.22)
NTSC | DVD: R1 | BD: A
Sparktank is offline   Reply With Quote
Old 8th December 2017, 10:28   #4  |  Link
varekai
Registered User
 
varekai's Avatar
 
Join Date: Jul 2006
Posts: 410
Ahh... that's a lot more complicated than I was hoping for... :/
I'll just leave that project, 'cause it's a bit over my head.

Thanks for the the input though, appreciate that!

Best regards,
varekai
varekai is offline   Reply With Quote
Old 13th December 2017, 09:46   #5  |  Link
Ben_Nicholls
Registered User
 
Join Date: Aug 2017
Location: Charlbury, UK
Posts: 18
Remember if your downscaling by half you can convert 4:2:0 to 4:4:4, something to bear in mind.
Ben_Nicholls is offline   Reply With Quote
Old 20th December 2017, 16:13   #6  |  Link
PeerVanHeuen
Guest
 
Posts: n/a
Quote:
Originally Posted by varekai View Post
Hello,

Is there a way to encode/recode/compress an Ultra-HD to 1080p BD or to 1080p mkv without getting washed out colors?
Done a few tests and I always get very pale colors.
I'm shure there is an explantions to this but I can't figure it out.
Is it even possible to downscale to 1080p and get "normal" full BD colors?
Yes, the latest betas of CloneBD (current: version 1.1.7.3) do a really great job at that.
Just start the GUI, click on the disc to open, select MKV and a suitable codec.

If you choose AVC or HEVC 8 bit, color space and HDR will automatically get converted (BT.2020 -> BT.709 and HDR->SDR with proper luminance mapping, not just "tuned up" like some makeshift solutions do).
So you really don't have to worry about anything.

nVidia GTX 10xx is strongly recommended, the conversion is very fast with that.
Otherwise a software/CPU mode is used and that requires a lot of patience.

Give it a go, the free version does all that, but it will blend an icon over the video.
  Reply With Quote
Old 25th July 2018, 11:13   #7  |  Link
Yoshi
Registered User
 
Join Date: Apr 2014
Posts: 30
lack of dithering with CloneBD

@PeerVanHeuen

Thanks for the hint however, at least after a quick test of version 1.2.2.1, CloneBD doesn't seem to apply proper dithering either which results in severe banding depending on the content (best footage to test this is the intro of Planet Earth II with the sun rising).
Yoshi is offline   Reply With Quote
Old 25th July 2018, 12:36   #8  |  Link
sneaker_ger
Registered User
 
Join Date: Dec 2002
Posts: 5,388
How do you know it's lack of dithering and not an artifact of the lossy video encoder?
sneaker_ger is offline   Reply With Quote
Old 25th July 2018, 12:49   #9  |  Link
Yoshi
Registered User
 
Join Date: Apr 2014
Posts: 30
I don't, I am assuming to be correct.

There isn't a lot of movement in that scene and the bitrate *should* be sufficient to encode it without banding given proper dithering.

In any case as long as I haven't overseen some magic option or preset, the end result shows severe banding which isn't present in the original, hence it's not what should be desired.
Yoshi is offline   Reply With Quote
Reply

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 06:00.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.