so I spent the last 4-5 hours reading every single thread in the
archives related to buffer~.

I have been keeping into consideration threads priority and buffer~’s
lightweight locking mechanism (b_valid and b_inuse flags).

I am writing a normalization routine to be used inside a more complex
object and here is what I came up with:

void myobj_normalize(t_myobj *x)
{
t_buffer *b = x->buf;

if (b && b->b_valid) {

float *table = b->b_samples;
long chan = x->chan;
long frames = b->b_frames;
long nc = b->b_nchans;
int i;

// don’t need to worry about threads priority
// when reading from a buffer~

float maxval = 0.;
for (i = 0; i < frames; ++i) {
float val = table[i * nc + chan];
float absval = fabsf(val);
if (absval > maxval) {
maxval = absval;
}
}

if (maxval > 0.) {

// now I need to write to buffer
// so threads priority become an issue

// defer to low priority

float scale = 1. / maxval;
defer_low(x, (method)myobj_doscale,0L,0,0L);
}
}
}

void myobj_doscale(t_myobj *x, double scale)
{
t_buffer *b = x->buf;
float *table = b->b_samples;
long chan = x->chan;
frames = b->b_frames;
long nc = b->b_nchans;
int i;

while (buf->b_inuse) ; // spin until buffer is no longer
// in use by the audio thread

buf->b_valid = 0; // set b_valid to false to prevent
// buffer~ access while editing

for (i = 0; i < frames; ++i) {
table[i * nc + chan] *= scale;
}

b->b_valid = 1; // restore buffer~ access

b->b_modtime = gettime(); // set new modification time
// so that any object referencing
// this buffer~ can update
}

So far the code seems to be working correctly but I am not sure it IS
correct.

1. Is it strictly necessary to defer methods that alter the buffer~
content in any way to low priority ?

2. Am I supposed to be using deferlow as above or is defer more
appropriate in this situation ?

3. Am I correctly understanding and using buffer~’s locking mechanism ?

Any comments highly appreciated.

Thank you.

- Luigi

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Moody friends. Drama queens. Your life? Nope! – their life, your story. Play Sims Stories at Yahoo! Games.

http://sims.yahoo.com/

I am reviving this thread because my hopes in the new SDK have been disappointed. I wish there was the code of poke~ so I could see Cycling74 approved buffer writing etiquette.

Can someone give me the real practice of the inuse, valid and dirty flags?

thanks

pa

did you see this, posted the other day by tim place?

http://blog.74objects.com/2009/03/22/accessing-buffers/

oli