Question / Help Is Lancsoz really the best filter?

Videophile

Videophile

Elgato
Hi Guys,

I recently read this thread on downscaling in OBS. At one point, it says

  • Bilinear (sharp)
  • Bicubic sharper
  • Lanczos (smooth)
Now, I stream a lot of BF4, and I downscale 1080p to 720p and have always used lanczos, but from this list, it looks like that may not be the best idea, as I am going for sharpness, not smoothness.

Here is a stream using the settings above, with 2500kbps and fast X264 preset. To me, it seems very blurry at times.
http://www.twitch.tv/ltroyalshrimp/b/520524184

Here is a friend of mine streaming. He has pretty much the same settings as I do, but his quality is immensely better. Start watching the video at 7:30 in.
http://www.twitch.tv/bbqlunch/b/520227473

So, is lanczos not the best option for BF4? Or an I doing something inherently wrong?

Latest log file.

Thanks,

-Shrimp

EDIT: Misspelled title. *FailFish*
 
Sapiens

Sapiens

Forum Moderator
The best filter is the one that you think looks the best. Sometimes one filter will make things look better than the other two depending on the content, so it's up to you to test and decide for yourself.
 
Boildown

Boildown

Active Member
LtRoyalShrimp said:
  • Bilinear (sharp)
  • Bicubic sharper
  • Lanczos (smooth)
Now, I stream a lot of BF4, and I downscale 1080p to 720p and have always used lanczos, but from this list, it looks like that may not be the best idea, as I am going for sharpness, not smoothness.
Click to expand...

Well, if you're going by the description, then Bicubic would be the best, because its clearly sharper than Bilinear.

But actually this is something I too have never tested. So I'll give it a whirl some time and form an opinion. Seems easy enough to test myself.


Edit: You're not using the same settings though:

http://r-1.ch/analyze-twitch-vod.php?url=http://www.twitch.tv/bbqlunch/b/520227473

vs.

http://r-1.ch/analyze-twitch-vod.php?url=http://www.twitch.tv/ltroyalshrimp/b/520524184

You're a veteran here, so I don't need to tell you, but for any other observers, he's spreading his 3000 bitrate over only 30fps, while you're at 40fps. So each frame in your stream has fewer bits, and of course looks blurrier. Apparently using the Fast preset instead of his Very Fast isn't enough to compensate for this. Also, if he's not using a capture card, there might be one fewer conversions between color modes on his end, not 100% sure how that works though.
 
Last edited:
Videophile

Videophile

Elgato
Boildown said:
Well, if you're going by the description, then Bicubic would be the best, because its clearly sharper than Bilinear.

But actually this is something I too have never tested. So I'll give it a whirl some time and form an opinion. Seems easy enough to test myself.


Edit: You're not using the same settings though:

http://r-1.ch/analyze-twitch-vod.php?url=http://www.twitch.tv/bbqlunch/b/520227473

vs.

http://r-1.ch/analyze-twitch-vod.php?url=http://www.twitch.tv/ltroyalshrimp/b/520524184

You're a veteran here, so I don't need to tell you, but for any other observers, he's spreading his 3000 bitrate over only 30fps, while you're at 40fps. So each frame in your stream has fewer bits, and of course looks blurrier. Apparently using the Fast preset instead of his Very Fast isn't enough to compensate for this. Also, if he's not using a capture card, there might be one fewer conversions between color modes on his end, not 100% sure how that works though.
Click to expand...
Yea, I tried to copy his settings exactly, still didn't work. Im so confused. Anyways, thanks!

-Shrimp
 
V

vbdkv

Member
Recently I've been experimenting with the filters, and I must say bicubic looks far better than lanczos when downscaling. With lanczos the edges become too sharp and adds strange anomalies around the edges. With bicubic everything is crisp, clear and edges are smoothed properly which makes it much easier to watch for the eyes. I've used lanczos for a long time as I've read pretty much everywhere that it was superior.

So from now on, bicubic is the filter I'm using.
 
L

Lain

Forum Admin
Lain
Forum Moderator
Developer
Hm, some people have been saying the same for certain cases. I'm going to have to do more tests with it.
 
M

Muf

Forum Moderator
LtRoyalShrimp said:
Now, I stream a lot of BF4, and I downscale 1080p to 720p and have always used lanczos, but from this list, it looks like that may not be the best idea, as I am going for sharpness, not smoothness.
Click to expand...
Lanczos is sharper than bicubic. They are both approximations of a sinc filter (as you would get from a fourier -> crop -> inverse fourier), but lanczos is a closer approximation. The rule is the sharper it gets the more ringing you get. Here is (an old) page explaining a few things about it with visual comparisons:

http://www.panotools.org/dersch/interpolator/interpolator.html
 
Videophile

Videophile

Elgato
Did a quick test myself.

input: 1080p60 from PS4 from HD60.

Downscale to 720p30 using Lanczos and Bicubic.

Bicubic does look better imo.
 
Videophile

Videophile

Elgato
Muf said:
Lanczos is sharper than bicubic. They are both approximations of a sinc filter (as you would get from a fourier -> crop -> inverse fourier), but lanczos is a closer approximation. The rule is the sharper it gets the more ringing you get. Here is (an old) page explaining a few things about it with visual comparisons:

http://www.panotools.org/dersch/interpolator/interpolator.html
Click to expand...
Lanczos seems to be causing weird pixelation/artifacting, which in turn makes it look like the video is worse quality.
 
M

Muf

Forum Moderator
LtRoyalShrimp said:
Lanczos seems to be causing weird pixelation/artifacting, which in turn makes it look like the video is worse quality.
Click to expand...
If by "pixelation/artefacting" you mean ringing, then that's normal. If you mean something else, it could indicate a bug in the Lanczos shader.

Can you post an unscaled image and an image scaled by OBS using Lanczos? I'd like to run a comparison.
 
Boildown

Boildown

Active Member
Can you do unlabeled photos, and then let us know which is which after the fact? I'd like to do blind comparisons.
 
Videophile

Videophile

Elgato
M

Muf

Forum Moderator
Boildown

Boildown

Active Member
Bottom three look better to me. Which downscale did they use?

Edit: They're not the same resolution. Is the bottom the source?
 
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