FFMPEG: 3 stereo sets into one 5.1 mix

[sparktank]

EDIT: using https://ffmpeg.org/ffmpeg-filters.html#amerge
Making it inputs=3 will give a proper 5.1 mix, opened in Audacity and it tested the channels.



I've 3 sets of audio that are stereo but each with specific mappings:
#1) L,R
#2) C,LFE
#3) SL,SR

There isn't an example on the FFMPEG trac site to show how to do this.
https://trac.ffmpeg.org/wiki/AudioChannelManipulation

This is what ffprobe reads:

Duration: 00:02:37.20, start: 0.000000, bitrate: 159994 kb/s
    Stream #0:0(und): Video: prores (HQ) (apch / 0x68637061), yuv422p10le(tv, bt709/unknown/unknown, progressive), 1920x1080, 150675 kb/s, SAR 1:1 DAR 16:9, 23.98 fps, 23.98 tbr, 24k tbn, 24k tbc (default)
    Metadata:
      creation_time   : 2019-03-14T05:43:13.000000Z
      handler_name    : Core Media Video
      encoder         : Apple ProRes 422 HQ
      timecode        : 00:59:56:01
    Stream #0:1(und): Audio: pcm_s24le (lpcm / 0x6D63706C), 48000 Hz, stereo, s32 (24 bit), 2304 kb/s (default)
    Metadata:
      creation_time   : 2019-03-14T05:43:13.000000Z
      handler_name    : Core Media Audio
    Stream #0:2(und): Audio: pcm_s24le (lpcm / 0x6D63706C), 48000 Hz, stereo, s32 (24 bit), 2304 kb/s (default)
    Metadata:
      creation_time   : 2019-03-14T05:43:13.000000Z
      handler_name    : Core Media Audio
    Stream #0:3(und): Audio: pcm_s24le (lpcm / 0x6D63706C), 48000 Hz, stereo, s32 (24 bit), 2304 kb/s (default)
    Metadata:
      creation_time   : 2019-03-14T05:43:13.000000Z
      handler_name    : Core Media Audio
    Stream #0:4(und): Audio: pcm_s24le (lpcm / 0x6D63706C), 48000 Hz, stereo, s32 (24 bit), 2304 kb/s (default)
    Metadata:
      creation_time   : 2019-03-14T05:43:13.000000Z
      handler_name    : Core Media Audio
    Stream #0:5(und): Data: none (tmcd / 0x64636D74), 0 kb/s (default)
    Metadata:
      creation_time   : 2019-03-14T05:43:13.000000Z
      handler_name    : Core Media Time Code
      timecode        : 00:59:56:01
Unsupported codec with id 0 for input stream 5

There's no meta info but the title card reads:

[pandy]

Use https://trac.ffmpeg.org/wiki/AudioChannelManipulation#a6mono5.1 as reference.
I think it is most convenient to use https://ffmpeg.org/ffmpeg-filters.html#join but also https://ffmpeg.org/ffmpeg-filters.html#channelmap or https://ffmpeg.org/ffmpeg-filters.html#pan-1 can be used to manually align channels.
There is no ready to use example but i think you are searching for syntax

[0:a:0][0:a:1][1:a:0][1:a:1][2:a:0][2:a:1]

instead

[0:a][1:a][2:a][3:a][4:a][5:a]