Created attachment 53598 [details] [review]
proposed fix

This will search for only two chains, and is thus incorrect. Smarter chain
position finding would be better.

Created attachment 53627 [details] [review]
proposed fix (2)

This is basically the same patch as above.
It makes gst_ogg_demux_read_end_chain stop when the last page of the *chain* is
found.
The current approach is to stop when the last page of *each logical bitstream*
in a chain is found. This approach is slow with oggs that have logical
bitstreams that end early in the phisycal bitstream, e.g. annodex files (where
the skeleton ends before the first data page).

Moreover this patch makes the chain finding work when there are logical
bitstreams that can't be decoded (that is when pad->elem_pad is NULL and the
pad->first_time can't be calculated).

the attachment #53952 [details] from bug #319986 contains this patch

Created attachment 53984 [details] [review]
proposed fix (3)

Created attachment 54077 [details] [review]
proposed fix (4)

updated to apply on HEAD

Committed version 3 of the patch, modified to apply to HEAD. The last version
added a bunch of unrelated functionality which I didn't want to review as part
of this patch (I suspect this version of the patch was intended for #319986).

Thanks for working through the issues with this patch, Alessandro.