Significant increase in (probably) comfort noise level at 13.2 kbps MASA transport signals with BASOP encoder

Basic info

• Float reference:
  • Encoder (float): e15ad0ad
  • Decoder (float): e15ad0ad
• Fixed point:
  • Encoder (fixed): d4fd91a6
  • Decoder (fixed): d4fd91a6

Bug description

Encoding an applause signal from selection test material with MASA at 13.2 kbps with DTX enabled and decoding that to EXT. The output transport signals have significant level increase in (presumably) comfort noise around 3-5 seconds into the sample.

Here are the spectrograms although the effect is much more noticeable by listening.

The bitrate is obviously low and the signal is hard but regardless the noise really hits as a disturbing change. Using float encoder, similar comfort noise is there but the level is more aligned with the overall signal.

Ways to reproduce

Box folder: ...\Box_EXTERNAL_IVAS_BASOP_VERIFICATION\issues\issue-1349

Use the command lines with the provided samples in Box.

IVAS_cod -masa 2 BASOP_Selection_MUSHRA-7ab_s10.met -max_band swb -dtx 13200 48 BASOP_Selection_MUSHRA-7ab_s10.wav test_0493.bs
IVAS_dec EXT 48 test_0493.bs 0493_BASOP_Selection_MUSHRA-7ab_s10.wav_13k2_48-48___EXT.wav