Vorbis granule position

I have a technical question about the vorbis granule position,
but I would like to put the question into context.

When a ogg vorbis stream is ripped using wget, fetch, or
streamripper under Linux or FreeBSD, the resulting file has
problems both with granule position and with a missing EOS. I
think I can figure out how to add an EOS, but is there a way
to determine the granule position in a stream if both the
previous and next granule positions are correct?

I am not the first person to notice this problem:

http://streamripper.sourceforge.net/phpBB2/viewtopic.php?t=1458

I understand that granule position of pages containing Vorbis
audio is in units of PCM audio samples, but I do not
understand if this quantity can only be calculated during
encoding or if it is possible to calculate it from the
captured file itself.
                                             
Finally, does there already exist a tool (sort of an 'fsck'
for ogg vorbis files) that will fix these files?

Regards,
 JM Rotenberry
 [email protected]