[PlanetCCRMA] amplitude overload problems

abi zerogrado@virgilio.it
Mon Aug 23 14:43:01 2004

Oded Ben-Tal a écrit :

it could be a broblem of bit depth, I had the same problem and I solved 
forcing jack with
16bit depth (my samples are at 16bit). If you don't use jack see the pd  
manual :

Pd's audio signals are internally kept as 32-bit floating point numbers, 
so you have all the dynamic range you could want. However, depending on 
your hardware, audio I/O is usually limited to 16 or 24 bits. Inputs all 
appear between the values of -1 and 1; and output values will be clipped 
to that range. Pd assumes a sample rate of 44100 unless you override 
this ( in Pd's command line or in the "audio setup" dialog).

Pd can read or write samples to files either in 16-bit or 24-bit fixed 
point or in 32-bit floating point, in WAV, AIFF, or AU format, via the 
soundfiler, readsf, and writesf objects.


>I'm encountering some amplitude overload problems when using pd and have 
>no clue how to track them not to mention fix them. I'm not even sure they 
>are related and they aren't consistent. Here is what I know:
>I'm running RH9. I have an audio quattro sound card connetced to a 
>keyboard and speakers (no mixer). I get audio from the keyboard as well as 
>midi in-out. 
>1) running pd with jack the output levels are sometimes overloading (i.e. 
>the test audio signal is a distorted scream; reducing the output levels in 
>working patches to %1 gets normal sound. On other occasions the level are 
>just fine (I think this depends on the boot process since stoping starting 
>jack or pd doesn't change tha outcome, rebooting sometimes does)
>2) running pd the sound input from the keyboard is overlaoding. strong 
>notes are always clipped; to get softer notes not to clipp I have to 
>reduce the amplitude on the keyboard itself to almost zero, even then 
>sending a strong midinote to the keyboard results in clipped input. 
>I played a bit with rosegarden to check the midi outputs and it worked 
>fine. I'm also running the same pd code (sending midi out to keyboard and 
>getting the audio in) under windows and it works fine. 
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