Energy overshoot on unvoiced segment for ISM-2 at 32kbps

Basic info

• Float reference:
  • Encoder (float): fbeb5ef8
  • Decoder (float): fbeb5ef8
• Fixed point:
  • Encoder (fixed): de24537b

Bug description

The fixed point synthesis of ISM-2 at 32.0 kbps can exhibit an energy overshoot compared to the original (or to the float synthesis) for some unvoiced content.

in the next figure, we see an example of the right channel.

From top to bottom :

• Original (right channel)
• Float synthesis (right channel)
• Fixed synthesis (right channel)
• spectrum

Ways to reproduce

Box folder: ...\Box_EXTERNAL_IVAS_BASOP_VERIFICATION\issues\issue-1159

IVAS_cod -ISM 2 NULL NULL 32000 48 dp07a5s07.wav bit
IVAS_dec_flt EXT 48 bit out.fxflt.wav

IVAS_cod_flt -ISM 2 NULL NULL 32000 48 dp07a5s07.wav bit.flt
IVAS_dec_flt EXT 48 bit.flt out.fltflt.wav