PSOne form PSN invalid header

I just tried to extract an iso from a 2-disk image (form PSN psone classics)

no information about why the header is incorrect


```
➜  NPUJ00662 psxpackager -i EBOOT.PBP --extract
PSXPackager v1.6.2 by RupertAvery

Input : EBOOT.PBP
Output: 
Compression Level: 5

Processing started: 09:38:26
Processing EBOOT.PBP

Invalid header
Processing completed: 00h 00m 00s
➜  NPUJ00662 

```