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[non BE] Fix 418 added in separate define

janssonfr requested to merge 418-using-the-correct-bitrate-for-unified-stereo-sid into main

Related to #418 (closed)

DTX/CNG for unified stereo was originally designed for a SID bitrate of 4400 bps. The SID bitrate has then been increased to 5200 bps in order to unify all different DTX/CNG modes. For unified stereo however the 4400 bitrate format is in practice kept and rest of the bits are just zero padded. This is marked with a “ToDo” comment in the code

A branch has been created that allows the unfied stereo SID encoding to use all available bits. It will not be bitexact for unified stereo DTX but the difference is small.

There is also a bug in the current code where the limitation to 4400 is not included in the conditions for itd and ipd encoding in stereo_dft_enc_write_BS. This in combination with how the 4400->5200 bps zero padding is done can give the result that too many bits are written to the bitstream. This happens if the sidegain coding uses the maximal number of bits. Increasing the bitrate to 5200 bps solves this problem.

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