BUG: Wrong Channel Mapping during Audio Encode to AAC

[Wontell]

Hello,
I noticed this bug for YEARS, since I started using NVEnc to encode videos back on 2080ti.

The issue:
Randomly, during audio encode, usually in movies where more than Single audio track encoded, the outputing AAC will get wrong channel mapping.

LFE channel turns into Cb channel
Ls and Rs turn into Lb and Rb

This is a movie with 4 audio tracks, 2 encoded, 2 left alone

Track #1:

Format/Info : | Digital Theater Systems
Codec ID : | A_DTS
Bit rate mode : | Constant
Bit rate : | 768 kb/s
Channel(s) : | 6 channels
Channel layout : | **C L R Ls Rs LFE**

Came out as this:

Format/Info : | Advanced Audio Codec Low Complexity
Codec ID : | A_AAC-2
Channel(s) : | 6 channels
Channel layout : | **L R C Cb Lb Rb**

Track #2:

Format : | DTS XLL
Format/Info : | Digital Theater Systems
Commercial name : | DTS-HD Master Audio
Codec ID : | A_DTS
Duration : | 2 h 2 min
Bit rate mode : | Variable
Bit rate : | 4 188 kb/s
Channel(s) : | 6 channels
Channel layout : | **C L R Ls Rs LFE**

Came out as this:

Format : | AAC LC
Format/Info : | Advanced Audio Codec Low Complexity
Codec ID : | A_AAC-2
Duration : | 2 h 2 min
Channel(s) : | 6 channels
Channel layout : | **L R C Cb Lb Rb**

This is a TV series, with 2 audio tracks, one streo not encoded and one 5.1 DTS That encoded into AAC, comes out allright

This:

Format/Info : | Digital Theater Systems
Commercial name : | DTS-HD Master Audio
Codec ID : | A_DTS
Duration : | 44 min 40 s
Bit rate mode : | Variable
Bit rate : | 4 153 kb/s
Channel(s) : | 6 channels
Channel layout : | **C L R Ls Rs LFE**

Comes out as this:

Format : | AAC LC
Format/Info : | Advanced Audio Codec Low Complexity
Codec ID : | A_AAC-2
Duration : | 44 min 40 s
Channel(s) : | 6 channels
Channel layout : | **C L R Ls Rs LFE**
Sampling rate : | 48.0 kHz

[Wontell]

P.S. I use FastFlix for encoding and this is a generated command, what I found myself, is that FastFlix lets us choose both 5.1 and 5.1 (Side) as option, but in your NVEnc FAQ i found only single 5.1 option, there is no 5.1 (Side) option, so this may be the issue?
I always select 5.1 (side) option in FastFlix, so even if this command is wrong, why some movies come out with correct channel mapping and others dont.

"C:\Users\ps4xo\AppData\Roaming\FastFlix_Codec\nvidia\NVEncC64.exe" --avhw --device 0 -i "I:\X-Files\9x21 The X-Files I Want to Believe (2008) [BDRemux].mkv" --crop 0,140,0,140 --video-metadata clear --metadata clear --video-metadata title="The X-Files I Want to Believe (2008) [BDRemux]" --chapter-copy -c hevc --vbr 4500 --bframes 4 --ref 3 --bref-mode middle --preset P6 --tier high --lookahead 32 --aq --aq-strength 15 --level auto --chromaloc auto --colorrange auto --colormatrix auto --transfer auto --colorprim auto --output-depth 10 --multipass 2pass-full --mv-precision Q-pel --avsync cfr --audio-copy 3 --audio-metadata 2?language=eng --audio-stream 2?:5.1(side) --audio-codec 2?aac --audio-bitrate 2?480k --audio-metadata 2?clear --audio-metadata 2?title="English | AAC 5.1" --audio-metadata 2?handler="English | AAC 5.1" --audio-disposition 2?unset --audio-metadata 3?language=eng --audio-disposition 3?comment --sub-copy 1,2,3,4,5,6 --sub-disposition 1?unset --sub-metadata 1?language='rus' --sub-disposition 2?unset --sub-metadata 2?language='rus' --sub-disposition 3?unset --sub-metadata 3?language='rus' --sub-disposition 4?unset --sub-metadata 4?language='eng' --sub-disposition 5?original,comment --sub-metadata 5?language='eng' --sub-disposition 6?original --sub-metadata 6?language='eng' -m default_mode:infer_no_subs --thread-affinity all=all --output-thread 1 --cuda-schedule spin --output-buf 128 --thread-priority abovenormal --thread-throttling off --tf-level 4 -o "I:\X-Files\9x21 The X-Files I Want to Believe (2008) [BDRemux]-fastflix-6626.mkv"