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#1 goal for the format: special codecs for file types that are most used currently yet can not be compressed by current tools.
basically this is compression for complicated (already compressed) file types.
so what you have to do is take file apart, and divide it into parts that can and that can not be compressed (which is why jpeg, png, docx, pdf that is compressed, can not be compressed further usually).. then compress the part that can be compressed with special codec designed for that format. All of this is done transparently to the user of course, and usually quite fast if done right.
But for each format (mp3, jpeg, png, pdf, docx, odt, etc), special codec is required. So there is a lot of development work to be done here. There are also no examples of such work, and only very few utilities do it - for instance, Stuffit has a lot of special compressors, but it is available only if you give out your credit card (no actual free trial), while most other utilities do not have anything but general codecs.
Reality is that most people compress things that are already compressed, so using zip, or rar or 7zip on most things people usually backup or send via email will not result in great savings, or sometimes savings at all. If you compress jpegs to send over email or upload somewhere or simply backup, you will not gain any compression. On the other hand, with special jpeg codec, you can expect 20%-30% gain on your full album of pictures.
For instance zip has one most common codec which is deflate. WinRar has single codec too.
Now .paf/pa/power will have 5-6 at least within next 2 years. So you can imagine how big the task is. But the gains are big too so it is worth it.
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