Spikes in OMASA LTV at 160 kbps with 16 kHz output happens also with ISM4 coding

Basic info

• Float reference:
  • Encoder (float): efe53129c9ed87a5067dd0a8fb9dca41db9c4add
  • Decoder (float): efe53129c9ed87a5067dd0a8fb9dca41db9c4add
• Fixed point:
  • Encoder (fixed): ac900052
  • Decoder (fixed): ac900052

Bug description

Using this combination, there are large spikes (and MLD of almost 80) caused by BASOP decoder. These are not present in the float decoder and it does not matter if encoder is BASOP or float. And this only happens with 16 kHz output (checked also 32 and 48 kHz).

See the plot below for the spikes. The spikes seem to be in the ISM channels as this is discrete coding bitrate for OMASA. No exact idea how long this has been present in the codec.

Ways to reproduce

Use float ENC to BASOP DEC.

./IVAS_cod -ism_masa 4 2 ltv48_OMASA_4ISM_2TC_ISM1.csv ltv48_OMASA_4ISM_2TC_ISM2.csv ltv48_OMASA_4ISM_2TC_ISM3.csv ltv48_OMASA_4ISM_2TC_ISM4.csv ltv48_OMASA_4ISM_2TC.met -max_band fb 160000 48 ltv48_OMASA_4ISM_2TC.wav test_0952.bs
./IVAS_dec EXT 16 test_0952.bs out.wav