Coding of noise signal with BASOP encoder produces significantly different transport output with specific sample at 32 kbps WB DTX MASA

Basic info

• Float reference:
  • Encoder (float): b63c033f
  • Decoder (float): b63c033f
• Fixed point:
  • Encoder (fixed): f66bba2c
  • Decoder (fixed): f66bba2c

Bug description

For a specific noise sample, there seems to be a significant difference how the signal is encoded by the BASOP encoder and the float encoder. See figure below

The difference is similar (and audible) regardless if BASOP decoder or float decoder is used. Note that this is transport channel output so no MASA metadata is involved.

Ways to reproduce

Box folder: ...\Box_EXTERNAL_IVAS_BASOP_VERIFICATION\issues\issue-1468

Use the command line and files from Box.

IVAS_cod -masa 2 BASOP_Selection_MUSHRA-7ad_s15.met -max_band wb -dtx 32000 48 BASOP_Selection_MUSHRA-7ad_s15.wav test_1561.bs
IVAS_dec EXT 48 test_1561.bs 1561_BASOP_Selection_MUSHRA-7ad_s15.wav_32k_48-48___EXT.wav

Quite similar effect happens also with another sample set which is with command line

IVAS_cod -masa 2 BASOP_Selection_MUSHRA-7ab_s14.met -max_band wb -dtx 32000 48 BASOP_Selection_MUSHRA-7ab_s14.wav test_0694.bs
IVAS_dec EXT 48 test_0694.bs 0694_BASOP_Selection_MUSHRA-7ab_s14.wav_32k_48-48___EXT.wav