[speex-dev] integerization

Christian.Buchner Christian.Buchner1 at epost.de
Fri Jun 27 14:28:27 PDT 2003

>> Just a little status update how that integerization is coming along.
>> I am trying to limit myself to 32 bit arithmetics. That means
>> not using any __int64 or long long datatypes at any point.

> If possible, it would be nice to restrict ourselves to 32x32->64
> multiplies, so the code could run on almost any architecture.

Right now I can choose from 2 implementations (with a #define).

a) one that uses 64 bit intermediate results

b) one that restricts itself to 32 bit precision on intermediates. However
   the two factors going into the multiplications will be normalized (with
   right shifts) such that the intermediate cannot overflow.

Interestingly enough, there is no significant difference in performance
(SNR) when switching between a) and b).

> One thing to note here is that it is only the "relative values" that
> count for the auto-correlation. That is, you can normalize it by
> autocor[0] and get the same results. 

Thanks, that might be very helpful.

--- >8 ----
List archives:  http://www.xiph.org/archives/
Ogg project homepage: http://www.xiph.org/ogg/
To unsubscribe from this list, send a message to 'speex-dev-request at xiph.org'
containing only the word 'unsubscribe' in the body.  No subject is needed.
Unsubscribe messages sent to the list will be ignored/filtered.

More information about the Speex-dev mailing list