[vorbis-dev] merging monty's branch

[Monty]

Hi folks,

I'm doing a merge of my current branch onto the mainline (for testing)
today.  I believe it to be stable.  Just a little more vorbisfile
testing.  After the merge, I have a few more patches to apply, then
onto cascading/coupling.

New stuff:

Floor backend 1 and residue backend 1; both are present, but the
mainline modes won't use either yet.  Naturally, both are enabled for
decoding future streams that use them.

Floor 1 is a piecewise linear approximation of the spectral envelope.
Advantages: more stable local spectral behavior (no more spreading
stereo image at lower bitrates), more control over tuning specific
error characteristics.  Disadvantages: it takes more bits than LSP,
but not by an absurd margin (20%-30% premiun).

Residue 1: Same as residue 0, but uninterleaved.  The advantages are
that this is faster and allows one to more easily exploit
adjacent-line structure in the MDCT, assuming that that's what the
codebook model wants to do.

Vorbisfile optimizations; I took HB's optimization patch, fixed a few
infinite loop problems in it, and then decided to go a little nuts
eliminating unneeded machine initializations and decoding work.  The
end result is that ov_open (and friends), ov_raw_seek and
ov_pcm_seek_page are more than 100x faster (and even faster than that
on a network file system), and the other seek functions (that do
actually require some internal background PCM decode to get sample
boundaries right) are a shade under 2x faster (again, much larger
margin on distributed file systems).

I also added an ov_test() function as a fast partial open that
verifies the vorbis-ness of a file (and loads the headers for
perusal), but doesn't seek to learn the chain structure or total
length.  A partially open file can then be fully opened using
ov_test_open().  

Libvorbis now has an official vorbis_packet_blocksize() function to
learn the block size of a packet without decoding it. Libogg also has
one new function, ogg_stream_packetpeek(), which fetches the next
packet in a logical stream without removing it from the stream head.

None of these changes should affect binary compatability with prebuilt
applications.

Monty

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