Find out resolutions in Photo CD (PCD) format images

[nyk]

Anyone know how I find out what resolutions are stored in a PCD (photo CD) format image?
"file" says:
"MPEG ADTS, layer I, v1, Monaural".

"identify" (from imagemagick) says:
"PCD 768x512 DirectClass 3.8mb".

But I know (from the shop I just went, where they used photoshop on OSX), that there are higher reolutions in there!

I saw that there's the program "hpcdtoppm", but I only find the manpage through google, no source or binary. But according to it's manpage, it could be of use here. Any idea what I can use to find out the resolution in that PCD file?