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OMASA Decoding to HOA3: Large differences between Float and BASOP

Basic info

  • Float reference:
    • Encoder (float): efe53129c9ed87a5067dd0a8fb9dca41db9c4add
    • Decoder (float): efe53129c9ed87a5067dd0a8fb9dca41db9c4add
  • Fixed point:
    • Encoder (fixed): n/a
    • Decoder (fixed): ac900052

Bug description

When decoding the attached OMASA bitstream to HOA, we see large differences between BASOP and Float decoder:

Max Diff = 33593 (102.5%),  No. Diff = 77914300 (8152056 runs)

Especially at 1:38.390:

Bildschirmfoto 2026-02-13 um 16.52.55.png

Ways to reproduce

Bitstream:

bit.zip

IVAS_dec HOA3 48 bit.192 out.wav

Original encoder commandline (corresponds to test_param_file.py::test_param_file_tests[ltv-OMASA 2TC 4ISM at br sw techs 13.2 to 512 kbps start 80 kbps, 48kHz in, 48kHz out, HOA3 out])

IVAS_cod -ism_masa 4 2 NULL ltv48_OMASA_4ISM_2TC_ISM2.csv ltv48_OMASA_4ISM_2TC_ISM3.csv ltv48_OMASA_4ISM_2TC_ISM4.csv ltv48_OMASA_4ISM_2TC.met ivas-codec//scripts/switchPaths/sw_13k2_512k_2fr_start_80k_omasatechs_4ism.bin 48 ltv48_OMASA_4ISM_2TC.wav bit.192