Downsampling by non-integer factor Filter requirement I am trying to implement a logic to downsample data in non-integer factor.Lets say,converting 48Ksps to 1344 samples per second.Have two step implementation of upsample by K ,and downsample by L is in my mind, such that K/L gives me the required ratio.

The thing that troubles me is the filter(if any) required in between the upsampling and downsampling. Can anyone help me understand the necessity of this filter?
Also is there any better methods to do so?
If the data is already bandlimited to below half the new sample rate, then a low pass filter may not be required.  If not, low pass filtering is required to prevent aliasing, which can corrupt your result.  Low pass filtering can be combined with Sinc kernel interpolation of all the new points needed at the new sample rate, e.g. only one step, no up/down pair of sample computations required.