Issue 476 in webp: Gif to webp artifacts / distortion on animation

[s… via monorail]

Status: New
Owner: ----
Labels: Type-Defect Priority-Medium

New issue 476 by s...@slik.com.au: Gif to webp artifacts / distortion on animation
https://bugs.chromium.org/p/webp/issues/detail?id=476

What steps will reproduce the problem?
1. Download gif from https://drive.google.com/file/d/1kh5PXv6FIjbkI582uJRFaeUeBSxHNOpq/view?usp=sharing
2.Convert gif to webp
3.Playing in Chrome there are black artifacts on the red background, usually where after change there is a trailing effect.

What is the expected output? What do you see instead?

The original gif is the intended result. We've experimented with different colours, and it produces the same result on the background when converted to webp

What version of the product are you using? On what operating system?

of chrome?
83.0.4103.116

Please provide any additional information below.

Attached are the original and resulting animations.

Attachments:
Original_animation.gif 618 KB
Resulting_animation.webp 213 KB

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[pascal.m… via monorail]

Updates:
Status: Accepted

Comment #1 on issue 476 by pascal.m...@gmail.com: Gif to webp artifacts / distortion on animation
https://bugs.chromium.org/p/webp/issues/detail?id=476#c1

Thanks for the report, i can reproduce the problem using 'gif2webp'

It seems any lossy compression with quality less than '-q 98' will indeed struggle with the red+black color mix.
But then the compression ratio is not that interesting compared to just pure lossless.

gif2webp QINSUR0120_Platinum_Balance_Transfer_680x400_v1.gif -min_size -q 98 -m 5 -mixed -o v_,mixed.webp => 464904 bytes
gif2webp QINSUR0120_Platinum_Balance_Transfer_680x400_v1.gif -min_size -q 100 -m 6 -o v_lossless.webp => 489946 bytes

For now, the safe way to proceed is to use lossless compression only with this sort of source that contains a lot of red area.

Thanks for the great sample! We'll keep investigating to see if we can reduce the lossy quantization artifacts on the U/V plane that leads to these black trails...

Attachments:
v_mixed.webp 454 KB
v_lossless.webp 478 KB

[jz… via monorail]

Updates:
Owner: pasca...@gmail.com

Comment #2 on issue 476 by jz...@google.com: Gif to webp artifacts / distortion on animation
https://bugs.chromium.org/p/webp/issues/detail?id=476#c2

(No comment was entered for this change.)

[jgbec… via monorail]

Comment #3 on issue 476 by jgbec...@gmail.com: Gif to webp artifacts / distortion on animation
https://bugs.chromium.org/p/webp/issues/detail?id=476#c3

I also have a similar issue, only with large rectangular artefacts. If I do the conversion as a lossless conversion, there are no artefacts, but the resulting image is quite large. If however, I do the conversion as a lossy conversion (even at 90% quality), I immediately get artefacts. I get the same artefacts when using '-mixed'.

The artefacts are present whether I'm playing in Chrome [Version 88.0.4324.192 (Official Build) (x86_64)] or Safari [Version 14.0 (15610.1.28.1.9, 15610)].

The commands used for the conversions were:

a_lossless.webp: `gif2webp -m 6 -q 100 a.gif -o a_lossless.webp`
a_lossy_90.webp: `gif2webp -m 6 -lossy -q 90 a.gif -o a_lossy_90.webp`
a_lossy_10.webp: `gif2webp -m 6 -lossy -q 10 a.gif -o a_lossy_10.webp`


It's also interesting to note that the size of the lossy image with quality 90 is more than 2x as large as the lossless image.

Attachments:
a.gif 154 KB
a_lossless.webp 156 KB
a_lossy_90.webp 435 KB
a_lossy_10.webp 139 KB

[yaron… via monorail]

Comment #4 on issue 476 by yaron...@cloudinary.com: Gif to webp artifacts / distortion on animation
https://bugs.chromium.org/p/webp/issues/detail?id=476#c4

similar issue to https://bugs.chromium.org/p/webp/issues/detail?id=554
attached result after code fix for: gif2webp Original_animation.gif -lossy -q 70 -o result_476.webp --> 313,582 (~50% saving in size)

Attachments:
result_476.webp 306 KB