Hi,
Sometimes I use Audacity to change the pitch of a song a few semi-tones without changing the speed. Most of the time this works ok, other times not so much. It can introduce a glitchy 'under water sound' and errors in the stereo image.
I recently did it again and it occured to me that this could be due to aliasing of the band limited audio, 44100 Hz typically, because of Nyquist ... stuff. I have only a general understanding of this and no idea how the pitch algorithm works. Then I resampled to 96000 Hz before pitch shifting and the shifted output was much improved.
Is there some math to guestimate the optimal/minimum upsampled frequency, for example based on the ratio of the input and output base frequencies?
Sometimes I use Audacity to change the pitch of a song a few semi-tones without changing the speed. Most of the time this works ok, other times not so much. It can introduce a glitchy 'under water sound' and errors in the stereo image.
I recently did it again and it occured to me that this could be due to aliasing of the band limited audio, 44100 Hz typically, because of Nyquist ... stuff. I have only a general understanding of this and no idea how the pitch algorithm works. Then I resampled to 96000 Hz before pitch shifting and the shifted output was much improved.
Is there some math to guestimate the optimal/minimum upsampled frequency, for example based on the ratio of the input and output base frequencies?