I am using PVRTexTool library to convert textures from several formats. With DXT5 I found out that quality parameter in Transcode function doesn’t have any significant effect. With ePVRTCNormal, ePVRTCHigh, ePVRTCBest output image remsins the same. Most disappointing is that NVIDIA texture tools (nvtt) produce better quality
The quality parameters will only affect PVRTC and ETC compression, and have no affect on the DXTC compressor. Whilst PVRTexTool does support compression to DXTC, it is not necessarily a compression format that we are supporting much hardware with, and our advice is to always use PVRTC preferentially on our hardware. So this means that unfortunately the DXTC compression has not had any significant work done on it for a long time now. NVidia on the other hand have DXTC as their primary compression format, and have invested significant time into their compressor, so the additional quality for this format is not surprising.
In a future release we plan to add the ability to use custom compressors, which would allow you to use, say libsquish to generate your DXTC textures. For now though I’m afraid if you do really want the best quality DXTC compression you probably will have to continue using other tools.
Thanks for your responce!
Is parameter affected both ETC and ETC2 formats? Since I am developing not for mobile devices I am interesting in ETC2 and DXT1/3/5 formats, PVRTC maybe interesting later