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MDCT-stereo at 48kbps for STV produces severely distorted output with BASOP encoder

Basic info

The output for MDCT-stereo at 48kbps coding the stv stereo file with the BASOP encoder and decoding with the float decoder is severely distorted and in general very different from the float-float output. The difference of the two signals (float minus basop) can be seen below:

Screenshot_2024-12-10_at_14.17.50

a main issue seems to be aliasing distortion, that is observed on the boarders of the frames e.g.

(basop - float)

Screenshot_2024-12-10_at_14.27.27

with the original for reference:

(float - float)

Screenshot_2024-12-10_at_14.27.37

This is only an example snapshot. Issues like this can be seen and heard across the whole item.

One source for these distortions could be the ITD.

Ways to reproduce

{BASOP} ./IVAS_cod -stereo 48000 48 stvST48c.wav stvST48c_float_48k.192

{Float} ./IVS_dec stereo 48 stvST48c_float_48k.192 stvST48c_float_48k.dec.wav