QUOTE(leggendario @ Nov 5 2006, 18:59)

QUOTE(Gambit @ Nov 5 2006, 08:03)

You can read the Vorbis docs, for complete header parsing info.
If you want to do it the easy way: The length value is stored in Samples, so you can convert that to hex and search for the value. It should be just a few bytes behind the "OggS" string.
I need a method without using .dlls, but only using files .ogg and an hex editor...
Which bytes exactly? I'm really noob about it...

What DLL, genius?
You take the samples length (foobar -> Properties, for example 3:30 would be 9261000 samples) convert the decimal value to hex(8D4FC8), reverse byte order (C84F8D), search for the value, edit, save. That's it.
I don't know what you hope to achieve by that, but if you don't know what you're doing, you better leave it like it is.