Encoder can create a wrong bitstream for all stereo bitrate < 48 kbps with dtx on

(Generic issue template)

When encoding a file in stereo at a bitrate lower than 48 kbps with the dtx option enabled, in the function stereo_dft_enc_sid_coh() at frame 444, the encoder tries to push an -1 index in the bitstream. This happens because cohBand[0] == inf

The input file is located at : _EXTERNAL_IVAS_BASOP_VERIFICATION\issues\FLT_issue-1246

Command line:

IVAS_cod -dtx -STEREO 13200 48 dm1aa1s12.wav bit13200

When the debugging is activated, the encoder interface will print the following error:

Internal fatal error: Indice with value 65535 exceeds the range of 2 bits (frame 444)

The encoding process continue, but this stops the decoder.

@norvell, I assigned you because of the DTX, but feel free to reassign. @multrus