Membrane.Bin.def_output_pad
You're seeing just the macro
def_output_pad, go back to Membrane.Bin module for more information.
Macro that defines output pad for the bin.
Allows to use one_of/1 and range/2 functions from Membrane.Caps.Matcher
without module prefix.
It automatically generates documentation from the given definition and adds compile-time caps specs validation.
The type Membrane.Pad.bin_spec_t/0 describes how the definition of pads should look.