How to use zlib compression during packaging at UE 5.1?

[Janghoon_Kang]

Hi, I’m trying to packaging my sample project with using Zlib compression. However, there’s no documents or informations for using zlib compressing at UE5.1 project packaging. Are there any ways to use zlib compression at UE5 project packaging?

[3dRaven]

Seems by default Zlib compression is only available for materials. You would need to write your own plugin to compress whole packages.

[Janghoon_Kang]

Yeah I already set Shader compression by ZLib at Engine-Rendering part. And now I found “NAME_Zlib” option at PakFileUtilities.cpp so that I changed Zlib at Package Compression Format (replaced from Oodle) and removed Kraken at Package compression method. But still error at IoStoreUtilities

[3dRaven]

I just tried replacing Oodle with Zlib. Left Kraken.
I worded it just like in IoStoreUtilities so uppercase Z the rest lower case
Packed fine and the project runs

Did another test replacing kraken with Zlib…also compiles fine. I’ll try a 3 x Zlib combo with materials next.

Edit: Ok so 3 x Zlib seems to fail during packing with ExitCode=-1073740940. Seems you can turn off “Use IO Store” in packing to mitigate this.

Trying a final repack => It was a success.

So you can set all 3 compressions to Zlib and turn of Use IO Store and it should pack ok.

If you want IO Store to work then the materials need to be set to the default compression.

Final note here is my engine version

[Janghoon_Kang]

Yes I also got same error code with using IoStore option. And I got error code (CompressedGroupSize > 0, CompressedGroupSize estimate seems wrong) when I replaced Kraken to Zlib option. It seems Epic only allows IoStore with using Oodle method. Thanks for testing several options for me and sorry to reply lately

[Edit]
Oh I found [AlternateTextureCompression] at Engine.ini, so that I will test with modifying that option and share it to you