Overlap-add zeroed for HQ-core at 24.4 kbps & 32 kbps (ISM)

With 4010db07 and this bitstream,

bit

Command line IVAS_dec MONO 32 bit syn

When the decoder enters the HQ-core, then the synthesis is zeroed for 40 samples at 32 kHz (1.25 ms) every frame. This seems to corresponds to an overlap not performed or empty overlap buffers.

Figure below shows the of segment of 6 HQ-core frames followed by TCX-20 (red is float, bleu is fixed point and yellow difference signal).