[vorbis-dev] Observations about the floating point data in vorbisfile

[Tomas Ogren]

Hello.

I noticed that when reading data with ov_read_float(), you can get
values outside [-1..1] when the stream is encoded at lower quality, but
with higher quality, the values trim down to inside [-1..1].
Looking at the plot from -q10, the data from ov_read_float seems
clipped.

I've made some plots of encoding the start of Rammsteins Feuer from the
xXx soundtrack (it's a pretty loud soundtrack, but max is still max.. ).
http://www.ing.umu.se/~stric/tmp/vorbis/
These are plots of data read with ov_read_file, printf()'d and fed into
gnuplot. The x axis is sample number, counting from sample 900k
(left,right,left,right,...)

Looking at ov_read(), it clips the data to [-1..1], but I have encoded
files where samples go up to 1.45 which I suppose isn't right.

Both 1.0 and 1.0rc3 show similar stuff.

/Tomas

-- 
Tomas Ögren, stric at ing.umu.se, http://www.ing.umu.se/~stric/
|- Student at Computing Science, University of Umeå
`- Sysadmin at {cs,ing,acc}.umu.se
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