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Energy/scaling issue for ISM-1 at all bitrates

Basic info

Bug description

In the middle of a voice segment, the energy if the fixed point synthesis is dropping compare to the floating point synthesis. When looking at intermediate signals, the same problem can be seen already after the downmix (ivas_input_dmx.id1.pcm). Interestingly, the difference seems to start at half frame and stop at half frame. This happens with and without metadata

From top to bottom :

  • float synthesis
  • fixed point synthesis
  • difference
  • ivas_input_dmx.id1.pcm float
  • ivas_input_dmx.id1.pcm fixed point
  • difference

image

From top to bottom :

  • ivas_input_dmx.id1.pcm float
  • ivas_input_dmx.id1.pcm fixed point
  • difference
  • spectrum (6dB between the 2 signals)

image

Ways to reproduce

Box folder: ...\Box_EXTERNAL_IVAS_BASOP_VERIFICATION\issues\issue-1186

IVAS_cod -ISM 1 cp06a1s04.wav.0.csv 128000 48 cp06a1s04.wav bit
IVAS_dec EXT 48 bit synfxfx.wav 

IVAS_cod_flt -ISM 1 cp06a1s04.wav.0.csv 128000 48 cp06a1s04.wav bit
IVAS_dec_flt EXT 48 bit synfltflt.wav

tagging @fotopoulou for awareness