# DSPs, DPMs, and DPFs

DSP programs are distributed in files called data processing modules (DPMs). These files use the extension .f41, and contain executable code for a family of algorithms. Algorithms in the family are called data processing functions (DPF). They can be referenced by a unique string generated by combining the family string ID that corresponds to the DPM with the function ID string that corresponds to the DPF. The string is formatted as dpm.dpt. Both the DPM and DPF have associated hexadecimal IDs that can be combined to uniquely identify the DSP function.

For example, the file echo.f41 is the DPM for echo cancellation. All of the DPFs in echo.f41 provide a type of echo cancellation functionality. The echo canceler DPM ID is echo and the associated hexadecimal ID is 0x16. For an echo canceler that has a filter length of 20 milliseconds and an adaptation rate of 100 percent, the DPF ID is ln20_apt100 and the associated hexadecimal ID is 0x0A00. Therefore, this echo DPF is identified by the string ID echo.ln20_apt100 (or the hexadecimal ID 0x160A00) formatted as dpm.dpf.

To list all function IDs in a particular family and their associated hexadecimal IDs, run the f41info program and specify the DPM file name for the family. For example, for the echo cancellation family of functions, type the following command at the prompt:

f41info tone

For more information about f41info and about DPM and DPF hexadecimal IDs, refer to f41info - Displaying DPF file resource usage.