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Very high MLD for ParamMC 5.1+4 at 96kbps 16kHz input

Basic info

Related to #1267 (closed)

  • Float reference:
    • Encoder (float): d3f01fcf
    • Decoder (float):
  • Fixed point:
    • Encoder (fixed): 182c2a50
    • Decoder (fixed):

Bug description

For 16kHz inputs to ParamMC, the BASOP Encoder exhibits high MLD values (30 and above) across all multichannel formats.

This holds true for non scaled inputs as well as ±10dB scaled inputs, with +10dB scaling producing the highest MLD results.

This issue seems to be most severe for this one 5.1+4 test item resulting in an MLD of 68.80.

There is a loudness difference of 2.84 LUFS visble in the below screenshots:

Float reference (-12.08 LUFS):

grafik

BASOP Encoder (-9.24 LUFS):

grafik

Comparison:

Bildschirmaufnahme_2025-05-14_um_17.53.10_1

MLD was measured on 16kHz outputs resampled to 48kHz, while loudness values are reported for the 16kHz outputs.

Ways to reproduce

Box folder: ...\Box_EXTERNAL_IVAS_BASOP_VERIFICATION\issues\issue-1583

./IVAS_cod_fx -mc 5_1_4 -max_band WB 96000 16 am3aa1s02_16.10dB.wav bit
./IVAS_dec_flt_ref 5_1_4 16 bit out.wav
Edited by Archit Tamarapu