Band-width switching issues in ISM format

In the ISM format coding, there is used WB low-rate coding mode for coding inactive segments of individual streams. At the decoder, there exists a band-width switching logic coming from the EVS. This switching is triggered every time when the low-rate mode is present in the ISM coding but there is actually no real band-width switching as triggered by the band-width detector by default. Consequently, this EVS-based band-width switching logic has a negative impact on the quality as it attenuates the high-band spectrum in a few frames after the low-rate mode segment.

It is thus desirable to not trigger the band-width switching in the ISm format when using the low-rate coding mode.