at9tool.exe is typically distributed as part of the or the specific PhyreEngine packages. It is distinct from the older at3tool (used for ATRAC3 on the PSP and PS3).
To convert a standard audio file for use in a game or theme, use the -e (encode) flag: at9tool.exe
For video games, background music often needs to loop seamlessly. at9tool.exe allows embedding loop points directly into the file header. at9tool
at9tool.exe -c -d 123456