FS#12223 - sinc resampling for rockbox
The attached patch implements sinc based resampling in rockbox.
I have only tested it stand-alone so far (i.e. the code outside of rockbox -- I am waiting for a replacement for my broken android phone to test it there).
There is (of course) quite some room for improvement.
Things which could be improved:
- buffer handling
- calculate the correct sinc spanning the whole table for downsampling. Then the downsampling and upsampling code would be the same (no need for sinc_increment, saving some additions). Also the result would be more accurate resampling.
- Save some memory by always calculating the correct sinc and putting it into resample_data. Would need to use fp_sincos() for that.
- Save some more memory by taking advantage of sinc's symmetry, only storing half of it in the table.
I know that I'm breaking the coding-style by using more than 80 chars in some lines. I will fix that when I have time. I wanted to get this code finally out to get some feedback after it sitting for two weeks (basically unchanged) on my HD.
This task depends upon