OMASA to FOA/HOA rendering has spikes in float

Basic info

  • Commit SHA: main
  • Platform: all

Bug description

Slightly duplicate of BASOP issue sa4/audio/ivas-basop#2438 but the problem is a bit wider.

Using the LTV OMASA test samples, a high MLD (about 48) is observed between BASOP and float for IVAS renderer when rendering FOA (or HOA). Inspecting the signals, this is seen

Screenshot_2026-04-22_at_15.56.32

There are spikes in the float signal. This seems to be a result of MASA stereo type detection not able to cope up with the given signal (same signal in both channels). Further inspection shows that this actually also happens with IVAS decoder as well and the spatiality of the output is completely lost in left-right direction in these cases. A simple fix will follow soon that will detect this situation. Both MASA and OMASA to FOA/HOA3 are affected and also MONO output will have some differences as it uses the same path.

Ways to reproduce

For example this

IVAS_rend -o out.wav -i ltv48_OMASA_4ISM_2TC.wav -if ISM4MASA2 -of FOA -fs 48 -im ltv48_OMASA_4ISM_2TC_ISM1.csv ltv48_OMASA_4ISM_2TC_ISM2.csv ltv48_OMASA_4ISM_2TC_ISM3.csv ltv48_OMASA_4ISM_2TC_ISM4.csv ltv48_OMASA_4ISM_2TC.met -fr 20