Downscale 1080p to 720p?

[Forteen88]

Hey
I wonder, how should I downscale 1080p video to 720p?
I usually use Spline64Resize() (because according to MeGUI it's a bit sharper than Spline36Resize()), although maybe there's a better way (like using NNEDI)?
Thanks

[Motenai Yoda]

Blackman is my choice, spline64 is too sharp imho...
nnedi should work only for upsample on power of 2

[Keiyakusha]

Forteen88
You probably don't want "something like nnedi" because it will be 1920x1080 -> 2xdownscale-> 960x540 -> normal resize-> 1280x720

IMHO spline36 is fine. First of all using too sharp resampler for downsizing is not necessarily will give you nicer look. Second is that spline 64 is noticeably slower than spline 36, but the difference is so small so it may be spotted only in some special cases. And even if so most of the time people only see the difference between them under high zoom but can't really tell which is better in reality.
Blackman probably also fine but I still prefer spline.

[Forteen88]

Ok, thanks for the info. Yeah, for sources that already are sharp it's unnecessary to use a sharper resize.

[wonkey_monkey]

For the mathematically inclined, is there any "beauty" in the idea of using a 2x upscaler like NNEDI, then doing a 3:1 downsize with a 5x5 Gaussian filter?

David

[markanini]

Is'nt there a script that's a NNEDI equivalent for downscaling related to SSSharp? Can remember the name of it for the life of me.

[markanini]

found it: automttap3

I guess the most insane overkill method for 1080 ->720 would be:
NNEDI x2 upscale, spline36resize downsize to twice the destination resolution and finally automttap3 x0.5

[Keiyakusha]

And what about actual results? Are they any better than just spline? (I don't even want to think how much slower it would be :Р)

[Leinad4Mind]

Well Spline36 is not mod16... Spline64 is it.... So I strongly recommend to use Spline64 (Is too my favorite xD). Blackman?! No thanks. ^^ It's too OLD... xD If i can remember Blackman existed to be better than LanczosResize. But Lanczos4Resize it's better but someway equal then LanczosResize(taps=4) but make a better job IMO, even better than Blackman, imo.

If it was an 480, or 720 to 1080. In other words, an upscale, I really recommend an SplineResizer. 64 is my choice. (SincResize does a great job on upscaling... but requires some knowledge on him.)
And NNEDI2, is great to upscale too! An wise choice.

If the anime is not an upscale... (many animes are upscale by the tv station) and u want to do an downsize, I recommend Lanczos4Resize. (If you are not so noob on resizers, you can try GaussResize, it's quite very good, but as SincResize, it requires some knowledge xD)

An alternative to downsize in a neutral way, and not using an sharp resizer you can go with: BicubicResize(1280,720,0,0.5) # the last value 0.5 means Neutral. If you put low values like 0.2 it will be blur, if you use high values like 0.8, it will be sharp.

best regards.:cool:

PS: Extra info go to:
http://avisynth.org/mediawiki/Resize
http://hermidownloads.craqstar.de/videoresizefiltercomparasion/
http://web.archive.org/web/20060827184031/http://www.path.unimelb.edu.au/~dersch/interpolator/interpolator.html

[Gavino]

Well Spline36 is not mod16... Spline64 is it....
mod16 (which usually refers to height or width) is not relevant here.
Spline36 is a 3-tap filter, using 36 (6x6) input pixels for each output pixel, while Spline64 is 4-tap (8x8).
But Lanczos4Resize it's better but someway equal then LanczosResize(taps=4) but make a better job IMO
Lanczos4Resize is just a synonym for LanczosResize(taps=4), ie they are exactly the same.
BicubicResize(1280,720,0,0.5) # the last value 0.5 means Neutral. If you put low values like 0.2 it will be blur, if you use high values like 0.8, it will be sharp.
The third parameter 'b' (here 0) is largely what controls the amount of blurring.

[2Bdecided]

And what about actual results? Are they any better than just spline?Yes. The more details there are in the source, the more dramatic the "improvement". For 1080>720 it's a small improvement. For 1080 > SD, it's a larger improvement.

Check this out...
http://forum.doom9.org/showthread.php?p=1211873#post1211873
...glacially slow!

IME It's almost impossible to encode it while maintaining that level of detail.

For 1080>720, I'd just use spline36resize.

Cheers,
David.

[Nico8583]

I'm sorry to bring up this topic but is there any new Avisynth filter to downsize 1080p to 720p ? I would like to downsize a 1080p h264 to 720p h264.
Thank you !

[StainlessS]

Nico8583, perhaps of interest:- http://forum.doom9.org/showthread.php?t=160038


EDIT: Arh, that project seems to be dormant, sorry, but rebuilt in May 2015, post #288 has link.

[Groucho2004]

I'm sorry to bring up this topic but is there any new Avisynth filter to downsize 1080p to 720p ? I would like to downsize a 1080p h264 to 720p h264.
Thank you !
I do this quite frequently, mainly because 720p is sufficient for the source material that can be found on many BDs (at least for my old eyes :rolleyes:).
I usually follow Sensei Didée's advice which is based on a less-is-often-more philosophy, see this post (http://forum.doom9.org/showthread.php?p=1748922#post1748922).

[Sharc]

I do this quite frequently, mainly because 720p is sufficient for the source material that can be found on many BDs......[/URL].
Absolutely, same here.
I am using spline16 often.

http://svn.int64.org/viewvc/int64/resamplehq/doc/kernels.html

[Nico8583]

Thanks to all :)
I hesitated between Bicubic and Spline36 and now between Bicubic(-0.5,0.25), Spline16 and Spline36 :D
What average bitrate do you use for 720p ?

[Groucho2004]

What average bitrate do you use for 720p ?
That very much depends on the source. I've done 720p encodes with 1000 Kbps (cartoon) and 12000 Kbps (source with artificial noise like "Black Swan"). I mostly use CRF encoding with a value of 18~20.

[Sharc]

Thanks to all :)
I hesitated between Bicubic and Spline36 and now between Bicubic(-0.5,0.25), Spline16 and Spline36 :D
What average bitrate do you use for 720p ?
I am using 720p mostly for putting the movie onto the NAS, encoding with CRF=20. Bitrate then becomes typically 3500 ... 5500 kbps depending on footage.

[Nico8583]

Ok thank you, so I must choose between Bicubic(-0.5,0.25) and Spline16/36 and I'll test filters with CRF=20. If you x264 parameters examples to encode to 720p I'll take it ;)

[Sharc]

Use the x264 presets, e.g. --preset medium or --preset slow.
For downsizing you may also consider bilinear. The slightly less sharp picture reduces the bitrate.

[MysteryX]

I'm currently using Bicubic(0, .75).

When I have the time, I'll look to integrate SSIM via AviSynthShader, which is now available in madVR and MPDN.
https://github.com/zachsaw/MPDN_Extensions/tree/master/Extensions/RenderScripts/SSimDownscaler

[Motenai Yoda]

I'm actually using spline36 for animation and blackman(minlobe) for RL
also try with the tune setting on film or on animation

[tormento]

I'm actually using spline36 for animation and blackman(minlobe) for RL
also try with the tune setting on film or on animation
Sorry to resurrect a old thread. I need to downsize 4k to 1080p. I was looking for this damn "blackman" filter and I can't understand if it's a plugin or a parameter. :)

[Groucho2004]

Sorry to resurrect a old thread. I need to downsize 4k to 1080p. I was looking for this damn "blackman" filter and I can't understand if it's a plugin or a parameter. :)
http://avisynth.nl/index.php/BlackmanResize#BlackmanResize

[tormento]

http://avisynth.nl/index.php/BlackmanResize#BlackmanResize
:thanks:

[Forteen88]

I need to downsize 4k to 1080p.You should probably use z.lib resizer,
https://forum.doom9.org/showthread.php?t=173986

I hope you're not using the default avs resizer because they produce chroma shifting.

I would prefer z_convertformat:
1)

ffvideosource("input.mkv") #8-bit source
z_ConvertFormat(1280,720,resample_filter="spline36",pixel_type="YUV420P10", dither_type="ordered")


2)

ffvideosource("input.mkv") #8-bit source
f3kdb(grainY=0,grainC=0,keep_tv_range=true)
z_ConvertFormat(1280,720,resample_filter="spline36",pixel_type="YUV420P10", dither_type="ordered")



P.S. f3kdb() - works internally in 16bit
z_resizers/z_convertformat works internally in high bit depth - if the input video is 8bit -> resizing in 16bit, if the input video is 10/12/14bit -> resizing in the input bit depth, if the input is 32f -> resizing in 32f.

[tormento]

You should probably use z.lib resizer
:thanks: