[Speex-dev] Distances in codebook search

Björn Thalheim s9268716 at mail.inf.tu-dresden.de
Mon Sep 11 01:43:15 PDT 2006


I recently measured the distances ndist[0][nb_subvect-1] which are used
to make the decicion, which codebook entries are to be used in
libspeex/cb_search.c (function split_cb_search_shape_sign).

For that I took a couple of audio books (all german speech), downsampled
the tracks to 8kHz and encoded them with "speexenc -n --bitrate 15000
..." (I used svn revision 11825).

Usually, the distances are in average 7.544420 and the deviation of the
distances is around 2.139503.

But the encoding of the data of one of these CDs shows for some tracks
average distances of around 12163.722796 and a deviation of 24312.252308
(that's just one example, there are more of them). I find this quite
interesting. More interestingly, it still sounds alright.

Is somebody of you interested in the raw audio files producing these
weird distances? I think these weird distances are a problem in the
codec. Maybe it is possible to find out where the problem is more
exactly than based on tracks (maybe frames).



PS: if anybody of you uses R, I could send the R workspace file, too.

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