Better understanding of downsampling (decimation) and upsampling (interpolation)

1. Which performs better downsampling upsampling or leaving the data Raw?
2. What is the difference between decimation and downsampling?
3. What is interpolation and decimation filters and why we need it?
4. What is the difference between upsampling and downsampling?

Which performs better downsampling upsampling or leaving the data Raw?

It depends on the level of certainty you need. If you don't need mathematical certainty and just want a heuristic, downsampling is faster and upsampling is more accurate. If you need to put bounds on the accuracy of your computation: it is possible but I can't help you with that.

What is the difference between decimation and downsampling?

Loosely speaking, “decimation” is the process of reducing the sampling rate. In practice, this usually implies lowpass-filtering a signal, then throwing away some of its samples. “Downsampling” is a more specific term which refers to just the process of throwing away samples, without the lowpass filtering operation.

What is interpolation and decimation filters and why we need it?

Decimation and interpolation are the two basic building blocks in the multirate digital signal processing systems. The decimator is utilized to decrease the sampling rate and interpolator to increase the sampling rate.

What is the difference between upsampling and downsampling?

Downsampling is the reduction in spatial resolution while keeping the same two-dimensional (2D) representa- tion. It is typically used to reduce the storage and/or transmission requirements of images. Upsampling is the increasing of the spatial resolution while keeping the 2D representation of an image.