Issue when computing bwe_exc_extended

Basic info

• Commit SHA: 6c9ddc40
• Platform: windows

Bug description

This has been identified while working on sa4/audio/ivas-basop#1406 (closed).

Basically, in rare occasion bwe_non_lin_prev_scale gets very high during inactive/unvoiced frame having low energy and if the next generic/tc frame has a sharp increase of energy at the beginning of the frame, then the bwe_exc_extended get scaled with a very large energy. The SWB_TBE has no mechanism to scale down the frame energy (minimum tbe "frame gain" is 1.0), thus this energy overshoot is not corrected.

Figure below shows the 2 channels of the original signal and the floating point synthesis at that place.

Ways to reproduce

Check synthesis of this bitstream at approx. 43 seconds

bit_new.dtx IVAS_dec STEREO 32 bit syn