DPL1 is an look-ahead digital peak limiter, the kind you would use as the final step to avoid clipping when mastering or mixing. It can be used as an effect on individual instrument tracks as well.

Latency is 1.2 ms rounded up to the nearest multiple of 8, 16 or 32 samples depending on sampling frequency. This amounts to 56 samples at 44.1 kHz, 64 samples at 48 kHz, and twice those values for 88.2 or 96 kHz.

In most cases you only need -k number_of_channels, which can be 1 to 16. The same gain reduction is applied to all channels.