[Tremor] I wanna increase the performance of the

[Roland Wintersteller]

functionmdct_backward()
In-Reply-To: <SEA1-F60yy86mRkgnZG00011b6b at hotmail.com>
Message-ID: <000e01c470c7$d4b28a90$9600a8c0 at CNH0WINTER>

In my understanding, the function mdct_backward() is the implementation
of the inverse discrete cosine transform in the way it is described in
the paper from Sporer, Brandenburg and Edler ? ?The use of multirate
filter banks for coding of high quality digital audio?.
(das.iocon.com/res/docs/ps/eusipco_corrected.ps)

The used algorithm fulfils a couple of important features:
-          in-place calculation: same buffer for input and output data
-          minimum of add, multiply, storage instructions
-          only little rounding errors

There are several other implementations of MDCT and IMDCT available.
Some people prefer FFT-based MDCT/IMDCT-implementations. The reason
therefore is, that for a number of processors ready-to-use
assembler-optimized FFT- functions are available. Nevertheless, the
IMDCT is one of the most time-consuming steps in the decoding process.

Regards, Roland



-----Urspr?ngliche Nachricht-----
Von: tremor-bounces at xiph.org [mailto:tremor-bounces at xiph.org] Im Auftrag
von moul karim
Gesendet: Freitag, 23. Juli 2004 15:22
An: Tremor at xiph.org
Betreff: [Tremor] I wanna increase the performance of the
functionmdct_backward()

Hello;
While I was analyzing the performence of a palyer, it looks that the
function mdct_backward() in file mdct.c takes me a lot of time, and I
wanna make my program runing 16 times more faster, so I think if I could
implement this function in hardaware it will be more faster. But to do
it, I need to understing what this function did exactely, I read it but
I'm not sure that I understand all its parts, and in the same time I
can't find anything that explain what this function did.
Can anyone help me or show me where I can find details about this
function.
Thank you .


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