[Plib-users] Changing the pitch/volume of non-looping sounds

[Christos D. <dim...@id...>]

I have used plib successfully to load and play 8-bit sounds. I have
found that looped samples, as in the examples given at the site, have
no problem handling envelopes. However, when dealing with one-shot
samples, which I play using playSound(), volume/pitch changes using
envelopes do not seem to work. I create a new envelope once, and I
load the sample once. This is the code that I use:

    crashSample[i] = new slSample(filename[i], sched);
    crashVolEnv[i] = new slEnvelope(1, SL_SAMPLE_ONE_SHOT);

Now... the question is.. where do I do AddSampleEnvelope()?
I tried doing it immediately after loading the sample:

    sched->addSampleEnvelope(skidSample[i], 0, 0, crashVolEnv[i],
SL_VOLUME_ENVELOPE);
    crashVolEnv[i]->setStep(0, 0.0, 0.0);

Then, in order to play the sample at the appropriate volume I just do:

    sched->playSample(crashSample[i]);
    crashVolEnv[i]->setStep(0, 0.0, appropriate_volume);

... and finish with

sched->update();

This did not work at all. The sound was always played at the same
volume. So I thought maybe the sample envelope gets lost after the
sample finishes playing. Thus I added the envelope everytime the
sample was played, but to no avail:

    sched->playSample(crashSample[i]);
    sched->addSampleEnvelope(skidSample[i], 0, 0, crashVolEnv[i],
SL_VOLUME_ENVELOPE);
    crashVolEnv[i]->setStep(0, 0.0, appropriate_volume);

...

    sched->update();


What am I doing wrong? Can you help?


-- 
Christos Dimitrakakis
IDIAP (http://www.idiap.ch/~dimitrak/main.html)