I'm using the Game Boy Advance to make entries for the Remix battles. As the GBA only supports 8-bit samples, this implies to convert the files of the bitpack because they usually are 16-bit samples.

So here is what I do:
- I convert all the samples to 8-bit with Audacity (but it doesn't keep the loop points)
- I open two .s3m files in OpenMPT, one with the original 16-bit samples, another one with the 8-bit copies
- I set each loop points for the 8-bit samples by copying the values for loop points in the .s3m file with 16-bit samples
- (then I use the .s3m file with the 8-bit samples to compose music)

Is there a way to convert the samples without all the manual work?

openmpt can convert between 8bit and 16bit naturally in the sampler by right-clicking on the waveform, it even has a default keybind of Ctrl+8

Oh thanks, it works well! I didn't know you could right click on samples, I'm more used to Schism Tracker