forums.ps2dev.org

[mrn]

yea,FFT is used everywhere, so I thought..
(i know, whenever i start a thread with these words somebody locks it, so....)
.. i thought it would be really smart to have fft precompiled
and offered as a luaplayer routine, in the same way as the battery or control functions are implemented.

fft (real, imag, N, inverse)

this would let us have many-many audio apps,
not to mention, if we would have pre-compiled DCT ...
u know what i am spaking about
h,

[KawaGeo]

I used FFT for my speech project many years ago. I knew about it. It required a huge amount of calculation to perform a relative large range of sound samples. I don't know if PSP could handle that much amount of calculation, sines and cosines and all. A table of sines and cosines helps to reduce the calculation but enough memory in PSP?
_________________
Geo Massar
Retired Engineer

[mrn]

No. Do not worry. for a 256, 512, or even 1024 -point FFT (as normally used in audio processing) you need to store only a piece of a cosine wave in a vector (which is of a length of the FFT-size). So, only some hundreds of Bytes. Then, you just pick up the numbers by downsampling this cosine wave by 2,4,8,16,etc when doing the butterfly multiplications...

Here is a really simple and fast FFT routine written in C.
http://www.jjj.de/fft/int_fft.c

I used it some yrs ago, simple to implement..
Hope, it is not a big problem to put it into our Luaplayer.
mrn

[KawaGeo]

If it were pre-implemented for Lua Player, it would be handy for speech translation, text-to-speech (easy) for the blind and speech-to-text (not so easy) for the deaf.

I sure hope 32MB RAM is big enough for the task.
_________________
Geo Massar
Retired Engineer

[Shine]

Most games and programs won't need it. I think the best idea would be to enhance Lua Player to load self-made PRX modules. A good place for it would be System/Library and write access from Lua Player scripts should be intercepted, to ensure that no script can create and execute unsafe code, which could damage the PSP. Then it is up to the user to manual copy libraries to the Library folder from sources she trust and some useful libs could be included in the standard Lua Player distribution and loaded on demand.

[mrn]

This library idea sounds great, I can provide some good fixed-point /floating-point FFT/DCT routines...
but unfortunately i do not have the time to learn how to create libraries for Luaplayer. Is there sbody willing to do that?

one of the fastest floating-point versions:
http://www.fftw.org/
..and this one was a fixed-point FFT:
http://www.jjj.de/fft/int_fft.c

[mrn]

[nevyn]

Sorry, the following is mostly off-topic. Skip if you're only interesting in fft.

Indeed, the idea of dynamically loading relevant libraries have sprung to my mind several times, I even worked out a great interface for it in my head and then forgot it. (as in interface design and architecture, not code) It allows extensibility without being slow (as in being interpreted). I'm right with you there, Shine.

Mrn, I didn't lock your thread because I disagreed with your ideas, I locked your thread because you were asking questions and bringing forth ideas that had already been debated and dismissed several times all over the forums.

I do believe that most of us have at least played with the idea of a full-fledged application environment within LuaPlayer. I know I have: that's my original vision with Lowser (tho' Lowser's a ridiculously simple (and badly written) app at the moment). Lowser and UIKit are supposed to bring an easy multitasked GUI and event toolkit (if I ever have the time to code it, that is).

[mrn]

[mrn]

hey, i just implemented fft in lua.
For N= 256 we need 40msec, which means 25 FFTs per second.
Quite slow for real-time audio processing.

Just a note: for speech recognition we need to process ~50 frames per sec,
where at least one FFT per frame (of course, plus a lot of other operations) is required. mrn

[mrn]