Interpolation is needed whenever the sound we want to hear is recorded/generated/played back at the same sample rate as the system making the final conversion to audible sound. Good interpolation doesn't add anything indeed, but naive interpolation does.
Say the sound was recorded at 44.1k, but the DAC is running at 48. Now whenever the output DAC asks for a sample, the recording will almost always be somewhere in between two of its samples. So we need some math to know what value to give the DAC.
Zero Order Hold = no math at all. Just take the value of the previous sample. Lots of Aliasing.
Linear interpolation = trivial math. Draw lines between samples and place the new samples on the line. Less aliasing, but still a lot.
Cubic interpolation = better math. Instead of lines between samples, draw curves. Even less aliasing, but still some.
Sinc = even better math. Still draw curves, but even better curves. Can get arbitrarily close to alias-free.
Can warmly recommend for anyone who wants to understand the nerdery better.
https://www.youtube.com/watch?v=UqiBJbREUgU
The "stair step" thing he mentions, which many folks imagine to be how digital sound works, is what ZOH is. Indeed no modern DAC does it. But tracker software apparently does.
Say the sound was recorded at 44.1k, but the DAC is running at 48. Now whenever the output DAC asks for a sample, the recording will almost always be somewhere in between two of its samples. So we need some math to know what value to give the DAC.
Zero Order Hold = no math at all. Just take the value of the previous sample. Lots of Aliasing.
Linear interpolation = trivial math. Draw lines between samples and place the new samples on the line. Less aliasing, but still a lot.
Cubic interpolation = better math. Instead of lines between samples, draw curves. Even less aliasing, but still some.
Sinc = even better math. Still draw curves, but even better curves. Can get arbitrarily close to alias-free.
Can warmly recommend for anyone who wants to understand the nerdery better.
https://www.youtube.com/watch?v=UqiBJbREUgU
The "stair step" thing he mentions, which many folks imagine to be how digital sound works, is what ZOH is. Indeed no modern DAC does it. But tracker software apparently does.
Statistics: Posted by Andreya_Autumn — Fri Apr 12, 2024 12:07 am