[vorbis-dev] encoding to fixed window length vorbis file

[c0g]

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Hi!
I want to encode wav file into fixed window length vorbis file. I don't
know if "window" is good name for that, but i mean MDCT buffer size.
This buffer is passed to mdct_backward() as "in" and it's size is
determined by "init->n" variable which is also passed to this function.
So, when I say "window size" I mean "init->n" value.
I noticed, that when decoding ogg vorbis file, window size is changing
and it's values for normal quality sound are: mostly 1024, somethimes
512 and very rarely 256.
I noticed also, that when decoding file resampled to 11kHz this value is
always 512 (for files I tested). When I resampled to 5,5kHz there was no
change in window size. I tried many combinations of oggenc options, but
the lowest window size, I obtained was still 512.

But I want to make file with window size = 256.

Is there way to accomplish that?

And now, why I need this.
I'm working on ogg vorbis decoder optimised for SUN SPARC machines. SUN
provides library (medialib, mlib) of multimedia functions, which are
written in VIS assembly, so they are fast. I want to optimise bacward
MDCT, and use medialib function for it. But here is a problem: medialib
IMDCT has hard-coded buffer size = 256. It is not possible to use it for
larger buffers (I think - I tried to use it twice on two halfes of 512
buffer on many ways). And the second problem is my project deadline is
comming soon, so I want to make decoder that works only on files with
windows size = 256 :P

Thanks in advance for any help!

- --
c0g at wp.pl
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