NHW - a free image codec

[nhw_pulsar]

Hello,

Just a very quick message to let know those who followed NHW, that the last version (v0.3.1+41) has now a good precision, in the sense that NHW image correctly resembles to the original image (for the developed -q9 to -q23 quality settings), while always keeping NHW efficient neatness.

So yes now it could be worth to adapt NHW to any image resolution. For me the best solution would be to process on the whole image dimensions, but it's really the bigger and harder to code. Another approach is the one of Martin, a great programmer and friend of mine, he has adapted NHW to 8x8, 16x16, 32x32, 64x64, 128x128, 256x256, 512x512 square sizes and he has then coded a very first (unoptimized) version of NHW that works with any image resolution by decomposing the image with these square sizes (prioritizing the largest square size first). The problem with this latter solution are the blocking artifacts (with a wavelet codec) but I have been told that deblocking filters could be quite efficient....

For now with my health, I will quietly continue to improve NHW precision, but maybe in the second half of 2026 if I am better, I will think about these solutions to adapt NHW to any image resolution, if I am alone, I think I will clearly choose Martin's solution because it is by far the fastest to deploy...

Cheers,
Raphael

[nhw_pulsar]

Hello,

Just a very quick update, as I think I'll release v0.3.2 in February, I wanted to make then a complete neatness study with objective nhw_neatness_metrics, but the new v0.3.1+42 version has (quite) worse neatness scores than v0.3.1+41, as reported by nhw_neatness_metrics, but I find that v0.3.1+42 has a better visual quality than v0.3.1+41, notably a better precision, it resembles more to the original image, so I didn't find for now a perceptual quality metrics that reflects visual quality according to my criterias and eyes...

Cheers,
Raphael

[nhw_pulsar]

Hello,

I am still thinking about Martin's (square) tiling solution for coding NHW to any image resolution, there are also some strong advantages, it is notably very more multithreading-friendly, SIMD-friendly, cache-friendly... but a very important thing is to know if we can design an efficient deblocking filter for my wavelet blocking artifacts, as I have hardly no knowledge in deblocking filters technology, it seems a very big investment and energy for me now...

Else I am ultra slowly working on NHW currently, but I hope that the next incremental improvement of v0.3.1+42 will lead to v0.3.2 version, hopefully with a real competitive precision with AOM and MPEG codecs, while still keeping NHW neatness which is a strong advantage for me...

Cheers,
Raphael

[nhw_pulsar]

Originally Posted by nhw_pulsar

Else I am ultra slowly working on NHW currently, but I hope that the next incremental improvement of v0.3.1+42 will lead to v0.3.2 version, hopefully with a real competitive precision with AOM and MPEG codecs, while still keeping NHW neatness which is a strong advantage for me...

Hello,

Just a very very quick update, I have released v0.3.1+43 version, at very first sight, I am satisfied with precision, so normally I'll see if I make other precision improvements but I think I'll transform this version into v0.3.2 later this month.

Cheers,
Raphael

[nhw_pulsar]

Hello,

Very quickly, I have released v0.3.1+44 which is better, I am waiting for releasing official v0.3.2, but I am sorry and I will get some anger, but I think I won't accompany v0.3.2 with a neatness study, as my nhw_neatness_metrics doesn't reflect for me image quality and what I call "neatness".For example, you can have a degraded image and sharpen it, my nhw_neatness_metrics will have very good score whereas the image looks horrible...

Cheers,
Raphael

[rwill]

Originally Posted by nhw_pulsar

For example, you can have a degraded image and sharpen it, my nhw_neatness_metrics will have very good score whereas the image looks horrible...

Heh... just like VMAF.

[nhw_pulsar]

Originally Posted by rwill

Heh... just like VMAF.

Hello rwill,

As I don't know VMAF, thank you for your professional feedback and information.I know that VMAF is largely acclaimed in the video compression community, especially at AOM, but as you point it has its imperfections... Measuring what I call the "neatness" of an image seems very difficult... Is it then offensing to say that VMAF is the less bad of the perceptual metrics?

Cheers,
Raphael

[rwill]

If you are using metrics like VMAF just for your own stuff its probably ok.

The ability to cheat in a metric becomes problematic if different actors start to compete on the basis of the metric. Then such a metric cannot be trusted. Thats why PSNR is so robust, you cannot cheat that one.

[nhw_pulsar]

Originally Posted by rwill

If you are using metrics like VMAF just for your own stuff its probably ok.

The ability to cheat in a metric becomes problematic if different actors start to compete on the basis of the metric. Then such a metric cannot be trusted. Thats why PSNR is so robust, you cannot cheat that one.

Yes that's right you can not cheat PSNR, but I really can not explain why PNSR can rate high some images that have not a great visual quality, and reversely...

[nhw_pulsar]

Hello,

Just a quick update, I think we can add a 10th element in the weight sequence to improve NHW precision and image quality, but currently I am too tired and it's too boring to test all the possible weights combinations (and there are millions of combinations), and I don't have the formula to derive the best weight sequence, so I must test currently each sequence combination with my eyes on different images...

However, v0.3.1+44 has for me an OK precision, and a better neatness than MPEG and AOM codecs, so I think, if I don't resume work on NHW in the meantime, I'll silently transform v0.3.1+44 into official v0.3.2 version next week, neatness will be still the strong point of NHW...

Cheers,
Raphael

[nhw_pulsar]

Hello,

I've finally improved the weight sequence (to the 10th order), so I have released v0.3.1+45 which is better, -as said, I'll release v0.3.2 next week-.

Cheers,
Raphael

[nhw_pulsar]

Hello,

Before v0.3.2, I have continued with the new v0.3.1+46 to improve the weight sequence (to the 11th order now).

Cheers,
Raphael

[nhw_pulsar]

Hello,

Just very quickly, I'll finally wait before releasing v0.3.2 to determine if I can level up the weight sequence to the 12th order, for a better image precision.I think and hope that the next iteration of the weight sequence order could have a competitive precision with AOM and MPEG codecs (however I can not test AV2- and ECM- intra).

Cheers,
Raphael

[nhw_pulsar]

Hello,

Very quickly, I have released v0.3.2 with an improved weight sequence up to the 12th order, for a better precision.

Cheers,
Raphael