High-frequency artifacts in 48kbps MDCT-Stereo encoding of frequency sweep from end of ltv48_STEREO.wav signal

Basic info

• Float reference:
  • Decoder (float): 2e062fa2
• Fixed point:
  • Encoder (fixed):c93084e6

Bug description

In the frequency sweep signal part of the stereo ltv signal, high-frequency artifacts are observed with the BASOP encoder:

The screenshot is from encoding with 48kbps, but I could also observe the same with 96kbps, but at a high frequency. Probably there is something going wrong at the starting frequency of the IGF range.

Ways to reproduce

Cut file:

ltv48_STEREO_sweep.wav

./IVAS_cod_fx -stereo 48000 48 ltv48_STEREO_sweep.wav bit
./IVAS_dec_flt_ref stereo 48 bit out.wav