Re: [LAD] Tutorial for programming with JACK

Hi experts

 

I followed your discussion about JACK API tutorial.

Actually i am beginner_from_zero in JACK programming.

 

Long long time ago i writed small JACK client, but i gotta problems with

x-runs and lost connections, and i not unterstood why.

 

Even if i read all this stuff, without tutorial and step_by_step examples

i can not programming stable JACK client.

http://jackaudio.org/files/docs/html/group__ClientFunctions.html

 

I found example 

https://github.com/harryhaaren/Linux-Audio-Programming-Documentation/blob/master/jackClient/jackClient.cpp

but i have some beginner questions about it.

 

Why it is written in C++ , not C ?

 

 float* inputBuffer = (float*)jack_port_get_buffer ( inputPort , nframes);

 float* outputBuffer= (float*)jack_port_get_buffer ( outputPort, nframes);

means "read" and "write" ?

 

If so then why callback func

process(jack_nframes_t nframes  )

have such structure ??

INPUT_READ

OUTPUT_WRITE

PROCESSING ?

 

 float* inputBuffer = (float*)jack_port_get_buffer ( inputPort , nframes);

 float* outputBuffer= (float*)jack_port_get_buffer ( outputPort, nframes);

  for ( i = 0; i < (int) nframes; i++)

  { // copy data from input to output. Note this is not optimized for speed!

    outputBuffer[i] = inputBuffer[i];

  }

It means that processed samples will go to output only @ next process() call ?

 

Why not 

INPUT_READ

PROCESSING

OUTPUT_WRITE ?

 

How can i detect (list) - all available ports:channels ?

How to automatic connect my client i/o ports to jackd ?

 

 jack_lsp -t

system:capture_1

32 bit float mono audio

system:capture_2

32 bit float mono audio

system:playback_1

32 bit float mono audio

system:playback_2

32 bit float mono audio

 

 

What means - 32 bit float mono audio ?

32 bit float - does JACK work with other sample formats ?

mono  - is it possible operate with interleaved stereo stream ?

audio - what else as audio ?

 

What about stereo stream ?

Must i create 2 ports ausL and ausR ?

 

  outputPort = jack_port_register ( client,

                                    "ausL",

                                    JACK_DEFAULT_AUDIO_TYPE,

                                    JackPortIsOutput,

                                    0 );

  outputPort = jack_port_register ( client,

                                    "ausR",

                                    JACK_DEFAULT_AUDIO_TYPE,

                                    JackPortIsOutput,

                                    0 );

If so, then how to write data and sync both seperate(d) channels?

With interleaved stream i do not care about sync between channels.

 

Tnx in advance @ all.

Alfs Kurmis

 

> Which leads me to my next question: are most JACK applications
> written in C/C++? I understand that programming as close to the
> hardware as possible is important for performance, but what about
> programming in a JVM language (I have Clojure in mind)? How
> reasonable is that?

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