Is there any introduction about the real method of guetzl?

[MrJiangSheng]

dear sir:
I have learned most of JPEG encoder,but many detil of guatzli is difficult to understand.Is there any introduction about the jpeg encoder?
thanks very much.

[jyrkialakuijala]

https://arxiv.org/abs/1703.04421 is a rough description

There is a selection of the quantization matrix (global optimization), and then performing the actual quantization (iterative local optimization).