search

FLIF-hub / FLIF

Free Lossless Image Format
Other
3.72k stars 229 forks source link

Comparison against AV1 lossless #491

Open paride opened 6 years ago

paride commented 6 years ago

Is there any plan to add a comparison against AV1 lossless? Some data is available here:

https://wyohknott.github.io/image-formats-comparison/report.html

and AV1 seems to have the best compression ratio.

jonsneyers commented 6 years ago

The comparison in the link above is not quite fair, since it is mixing 4:2:0 chroma subsampled and non-chroma subsampled and calls both of them "lossless", while the former actually has only half the information. So if you look at the table there, you have to take into account that only jxr, flif, kdu, webp, openjpeg, and mozjpeg are actually lossless. The others (daala, vp9, av1 and bpg) are only lossless w.r.t. the 4:2:0 image, so w.r.t. half of the information.

To do a proper comparison, you would need to compare to AV1 lossless in 4:4:4 mode (no chroma subsampling). I do not know to what extent AV1 already has a good encoder available for that.

paride commented 6 years ago

Thanks @jonsneyers. Are you sure the comparison is mixing 4:4:4 and 4:2:0 data? It says:

The image set is comprised of 50 images from the subset 1 and subset 2 maintened by Xiph. All images are YCbCr 4:2:0 Y4M files.

and then

Each Y4M image is exported to 4:2:0 PNG, YUV and PPM files

so it seems to me that everything is done with 4:2:0 subsampled images.

jonsneyers commented 6 years ago

Not really. PNG and PPM only support 4:4:4.

kliberty commented 6 years ago

@jonsneyers It looks like the images all started out as 4:2:0 Y4Ms. There shouldn't be an extra information in the PNGs than in the orignal Y4Ms.

magicgoose commented 5 years ago

There shouldn't be an extra information in the PNGs than in the orignal Y4Ms.

by usual definition of what is "information", these PNGs have to hold more information.
this isn't going to be a correct comparison, unfortunately.