AVIF: reduce number of quality levels from 64 to 32
Posted: Tue Jan 31, 2023 1:43 pm
I've been experimenting with the new .avif format lately.
So I've taken a .jpg image and converted it to .avif using different quality levels to learn how avif ticks.
Instead of jpg's quality percentage slider that ranges from 0% (ultrabad) to 100% (overkill),
avif has a min&max quantifier for colour
and a min&max for alpha channel.*
You may input values ranging from 0 to 63.
0 is the best.
63 is the worst.
So you'd think there are 64 possible quality levels.
I started with colour quantifier min=0 & max=30, then min=0 & max=29 and so on...
Here are the results:
As you can see, q29 and q28 are the same, q27 and q26 are the same etc.
Every second quality setting is redundant!
Conclusion:
Why does .avif offer 64 levels of quality, if there are in fact only 32 possible outcomes?
IMHO the possible input range should be reduced from 0-63 to 0-31.
*Note: The alpha channel quantifier only applies to images that feature transparent parts. If there are none, it does nothing.
So I've taken a .jpg image and converted it to .avif using different quality levels to learn how avif ticks.
- avif settings.png (10.81 KiB) Viewed 1714 times
avif has a min&max quantifier for colour
and a min&max for alpha channel.*
You may input values ranging from 0 to 63.
0 is the best.
63 is the worst.
So you'd think there are 64 possible quality levels.
I started with colour quantifier min=0 & max=30, then min=0 & max=29 and so on...
Here are the results:
- why 64.png (7.03 KiB) Viewed 1712 times
Every second quality setting is redundant!
Conclusion:
Why does .avif offer 64 levels of quality, if there are in fact only 32 possible outcomes?
IMHO the possible input range should be reduced from 0-63 to 0-31.
*Note: The alpha channel quantifier only applies to images that feature transparent parts. If there are none, it does nothing.