Correction of some overflow operations

Basic info

  • Float reference:
    • Encoder (float):
    • Decoder (float):
  • Fixed point:
    • Encoder (fixed): b0d052d7
    • Decoder (fixed):

Bug description

Two distinct undesired overflows were identified, both impacting bit‑exactness.

  1. Normalized correlation initialization
    The first overflow occurs during the initialization of the normalized correlation. Correcting it may slightly affect ACELP operating points. Only minimal differences were observed in the short version of the self_test.
  2. TCX operating point
    The second overflow affects the TCX operating point. A few differences were observed, with the corrected spectrum being closer to the floating‑point reference. No subjective differences have been found so far.

Ways to reproduce

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

For the first cases, frame 1040
IVAS_cod -dtx -stereo 24400 32 stvST32n.wav bit 

For the second case, frame 994 in the else part: 
ivas_cod -dtx -stereo 48000 32 stvST32n.wav bit
ivas_dec mono bit mono.wav
Edited by vaillancour