On Fri, 2015-10-09 at 01:09 -0300, Alexandre Torres Porres wrote:
hi, I was testing a lower samplerate with block in the parent patch, and listening to it.
It would be interesting to know what patch you used to _listen_ to your experiment. The attached patch simply shows that a down-sampled sine still looks ok.
sound is ruined in a way that is not explained or visible within what's going on in the patch. see attachment. If you lower it in the settings then it's fine... I really wonder why.
First, the help of [block~] and [switch~] states that they cannot be use together with [dac~] and [adc~] in the same canvas. In order to listen to that down-sampled sound, the signal needs to pass an [outlet~] which also does re-blocking with different methods that can be specified by arguments (pad, hold, lin). All of them are quite simple and cause artefacts. When you set a low sampling rate in the Pd settings, most likely the audio-backend will resample the output of Pd to match the sample rate of the audio card. The resampling algorithm used here is much better and thus you don't get that heavy artefacts.
By the way, on a second note, I lowered it down to 1Khz and could lis ten a 440Hz sine wave alright, but getting closer to 500Hz, the sound quickly disappears. Not that this is really important, just curious.
Have you ever heard of the Nyquist-Shannon sampling theorem? The sampling frequency needs to be at least twice the maximum frequency you intend to sample (play or record). Anything above will be lost (if filtered correctly, or else it will cause aliasing).
Roman