Bandwidth Extension problems in 7.1.4 at 96 kbps and 64 kbps

Basic info

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

Bug description

For some items selected for P800-7, there are audible artifacts in the BWE region. this occurs e.g. for cat2, items 1 and 6 and cat4, items 2 and 3. The mentioned items sound worse than the next-lower bitrate. The issue appears for 96 and 64 kbps in full-chain fixed-point output, but only at 96kbps for mixed output. So, it does NOT occur for 64kbps float enc -> fixed dec and it does occur for 96kbps fixed enc -> float dec. This hints at an encoder problem. At least from visual inspection of the spectrograms, it looks different from e.g. #2017 (closed) and #2016.

Perceptual impact is quite audible, for me worse than the next-lower bitrate which does not have it, so 64 or 48 kbps, depending on if it is mixed or fx full-chain. It does not occur in all items, but in many of the speech (!) items. The music items do not have it, but seem to also suffer from something like #2014 (closed) or #2010 (closed).

This particular example below happens for -36dB only

Float full chain 96kbps, item is cp07a4s03:

Fixed-point full chain:

Ways to reproduce

Box folder: ...\Box_EXTERNAL_IVAS_BASOP_VERIFICATION\issues\issue-2021

IVAS_cod_fx -mc 7_1_4 96000 48 20ms_aligned_files_concatenated.wav bit
IVAS_dec_fx BINAURAL 48 bit out.wav