FEATURE REQUEST: explicit backend selection on LRZIP

[Else00]

Hi Keka team,

Thanks for Keka, it's a really helpful archiving tool!

I've been using the lrzip option for compressing large files and have a suggestion regarding the controls. Currently, the "compression level" slider in the Keka GUI controls which backend algorithm lrzip uses internally, rather than just setting the level for one algorithm.

Based on my testing and looking at the output (like with lrzip -i), I've observed that the levels on the slider correspond to these lrzip backends:

• Level 0 (Store): Uses lrzip -n (rzip pre-processing only).
• Levels 1-4: Use lrzip --lzma (with varying levels).
• Level 5 (Slow): Uses lrzip -z (rzip + ZPAQ).

Lrzip natively supports selecting different backends explicitly using command line options like --lzma, -b (BZIP2), -g (GZIP), -l (LZO), -z (ZPAQ), and -n (no backend). These options offer distinct trade-offs in speed and compression ratio.

My suggestion is: could Keka add a direct way to select the lrzip backend algorithm in the UI? Perhaps a dropdown menu?

If an algorithm that supports level adjustments (like LZMA, BZIP2, or GZIP, which use lrzip's -L option) is selected, the standard compression level slider could then appear to set the level for that specific algorithm (from 1 to 9 in lrzip's CLI). For algorithms that don't use a standard level in the same way (like LZO, ZPAQ, or "No backend"), the level slider wouldn't be relevant and could be hidden or disabled.

This change would give users clearer control over which lrzip method is used and help them better balance speed and compression needs.

Also, as a quick side note: I noticed the lrzip version included with Keka seems to be 0.631, while the latest standalone is 0.641.

Thanks for considering this request!