This patch also adds a description how the heuristic works and mentions that
there is a scaling factor that can be adjusted if there is audible clipping.
Since commit e32a408b3c, we silence the
input memblock in order to give the resampler enough input samples, if
necessary.
But if there is no need to resample the hrir, the resampled memblock is
actually the same as the input memblock. Thus, we have to make sure that
we do not silence it in this case.
The sink has different frame size than the sink input, so
the max_request and max_rewind values of the sink input need
to be converted when setting the sink max_request and
max_rewind values.
The conversion is already done correctly in
sink_input_update_max_request_cb() and
sink_input_update_max_rewind_cb().
It provides a virtual surround sound effect.
v2: Normalize hrir to avoid clipping, some cleanups
v3: use fabs, not abs
v4: implement changes proposed by Tanu Kaskinen
v5: likewise
v6: use channel map from hrir file
v7: remove hrir_ss and hrir_map form userdata
v8: update naming of sink
