I have just written an MSP pitch detector object in java. It works perfectly but has a very high load on the CPU. In fact, if I use a signal vector size of more than 256 it causes clicking artefacts in the audio. The code isn’t really that big and I am using a brand new intel mac book 2.2 GHz machine.

Is this because of some speed limitation of using mxj quickie to build java objects? How could I improve the speed?

I am normally a C programmer and have coded much much larger things that run in real-time as VST plug-ins for example – and they generally are not that much of a burden on the CPU. I know Java is slower than C but I didn’t expect it to be quite so limiting, is there something I am doing wrong?

Alternatively, if anyone could point me to a good introduction to programming Max/MSP objects in C I would be very grateful (apologies as this question prob should go in the other forum but the first question should be here…).

I’d be very happy if someone could point me in the right direction,

Many thanks,

Adam

I could take a look at your code if you want. Things to avoid
are unnecessary object allocation, method call overhead,
etc. Generally having a knowledge of what the JVM will do
when it executes certain instructions.

I generally tend to think as if I am writing C code when writing
mxj~ stuff and stay as much as possible with the primitive constructs
of the java language.

Hope this is helpful.

Topher

On Oct 24, 2007, at 07:54 AM, Adam Stark wrote:

>
> Hi,
>
> I have just written an MSP pitch detector object in java. It works
> perfectly but has a very high load on the CPU. In fact, if I use a
> signal vector size of more than 256 it causes clicking artefacts in
> the audio. The code isn’t really that big and I am using a brand
> new intel mac book 2.2 GHz machine.
>
> Is this because of some speed limitation of using mxj quickie to
> build java objects? How could I improve the speed?
>
> I am normally a C programmer and have coded much much larger things
> that run in real-time as VST plug-ins for example – and they
> generally are not that much of a burden on the CPU. I know Java is
> slower than C but I didn’t expect it to be quite so limiting, is
> there something I am doing wrong?
>
> Alternatively, if anyone could point me to a good introduction to
> programming Max/MSP objects in C I would be very grateful
> (apologies as this question prob should go in the other forum but
> the first question should be here…).
>
> I’d be very happy if someone could point me in the right direction,
>
> Many thanks,
>
> Adam

Using the benchmark message allows you to quantify any optimizations
that you might be making
and could be helpful if you are not aware of it. See the mxj~
examples for use of the benchmark
message.

T

On Oct 24, 2007, at 07:54 AM, Adam Stark wrote:

>
> Hi,
>
> I have just written an MSP pitch detector object in java. It works
> perfectly but has a very high load on the CPU. In fact, if I use a
> signal vector size of more than 256 it causes clicking artefacts in
> the audio. The code isn’t really that big and I am using a brand
> new intel mac book 2.2 GHz machine.
>
> Is this because of some speed limitation of using mxj quickie to
> build java objects? How could I improve the speed?
>
> I am normally a C programmer and have coded much much larger things
> that run in real-time as VST plug-ins for example – and they
> generally are not that much of a burden on the CPU. I know Java is
> slower than C but I didn’t expect it to be quite so limiting, is
> there something I am doing wrong?
>
> Alternatively, if anyone could point me to a good introduction to
> programming Max/MSP objects in C I would be very grateful
> (apologies as this question prob should go in the other forum but
> the first question should be here…).
>
> I’d be very happy if someone could point me in the right direction,
>
> Many thanks,
>
> Adam

Thanks for your replies. It would be great if you could have a look at my code. I have attached the java file. The function causing the problems is the pitch_YIN function.

I also have one more question which is about C coding Max/MSP objects – so far, all the examples I have seen so far in C have been massively complex, uncommented and unexplained. The Java equivalent is so simple. Is there a simple C example somewhere or a good guide? Or is it generally complicated?

I’m very very appreciative of your help,

Thanks

Adam

The c external api is covered in writing max/msp externals by david
zicarelli.

It is not overly complicated. Just a little different.

I agree that there could be a higher level c api for externs. I was
working on a similar object to mxj called cfunk that addresses these
issues by allowing you to write in a similar way but in c instead of
java .I have stopped development of cfunk but perhaps I will finish it
up someday or someone else is interested in taking it over.

volker.

On 25 Oct 2007, at 15:19, Adam Stark wrote:

> Hi Topher,
>
> Thanks for your replies. It would be great if you could have a look
> at my code. I have attached the java file. The function causing the
> problems is the pitch_YIN function.
>
> I also have one more question which is about C coding Max/MSP
> objects – so far, all the examples I have seen so far in C have
> been massively complex, uncommented and unexplained. The Java
> equivalent is so simple. Is there a simple C example somewhere or a
> good guide? Or is it generally complicated?
>
> I’m very very appreciative of your help,
>
> Thanks
>
> Adam
>

Yes, that is a good suggestion and would make it run much faster. I also found another problem. This is maybe very obvious to more experienced Java users but I am new to using Java for signal processing: I found that, in my loop, when I calculated the square of a number using:

Math.pow(x,2);

my function took 19ms to do it’s calculations. However, when I used:

x*x

the processing time was reduced to just 3ms.

Anyway, thank you everyone for your help,

Adam