[theora] Indexless interpolation search seeking code

[xiphmont at xiph.org]

>> "An index is only marginally useful in Ogg for the complexity added; it
>> adds no new functionality and seldom improves performance noticeably.
>> Empirical testing shows that indexless interpolation search does not
>> require many more seeks in practice than using an index would."
>>
>> I am keen to see seeking code which is almost as fast as seeking with an
>> index. Is the code used in this empirical testing online somewhere or
>> otherwise available?
>
> IIRC that that quote dates from pre-Theora, and I assume it would relate to
> Vorbis-only files using libvorbisfile.

Actually, I just wrote that recently.

Fast seeking in a generalized Ogg file is no different from the
seeking implemented in libvorbisfile.  I hadn't written any such code
(outside of vorbisfile) because I'd been told it had been implemented
in liboggz/oggplay.  Is this not the case?

Monty