Creating Octagonal M4a to embed into a video

[jakejeffery]

I am looking for a means to create from 4 stereo tracks an octagonal track to embed into a video file. This cannot be 7.1 or 8 channel as i cannot have an LFE track. I currently can do this by converting to a wav file, then on afconvert converting to octagonal and then embedding through ffmpeg. However i am trying to do this all through ffmpeg.

Is there any way to do the following through ffmpeg with octagonal audio and speaker layout as Front: L C R, Side: L R, Back: L C R

ffmpeg -loglevel info -i FileA.m4a -i FileB.m4a -i FileC.m4a -i FileD.m4a
-filter_complex "
[0:a] channelsplit=channel_layout=stereo [A1][A2];
[1:a] channelsplit=channel_layout=stereo [B3][B4];
[2:a] channelsplit=channel_layout=stereo [C5][C6];
[3:a] channelsplit=channel_layout=stereo [D7][D8];
[A1][A2][B3][B4][C5][C6][D7][D8]amerge=inputs=8[out2];[out2] pan=octagonal| c0 = 1.0*FL | c1 = 1.0*FR | c2 = 1.0*FC | c3 = 1.0*LFE | c4 = 1.0*BL | c5 = 1.0*BR | c6 = 1.0*SL | c7 = 1.0*SR"
-strict experimental FileE.m4a

[El Heggunte]

By "octogonal" you mean 8.0, I presume.

Well, with or without ffmpeg, you would have to generate a multichannel output whose 'channel mask' = 1867 (decimal value).

And keep in mind that not all compressed audio formats (if any) support the 8.0 channel layout.
Probably you will have no other choice than storing an uncompressed stream in a MOV container

EDIT: just checked, AAC supports the 8.0 channel layout, according to https://github.com/nu774/qaac/wiki/Multichannel--handling

[jakejeffery]

Right now im able to compress a wav to an MP4 container temporarily. However i can only do it through afconvert on mac and not ffmpeg, which is weird cuz i can only generate the wav from ffmpeg but i cant compress it to MP4 in ffmpeg. I have to go to afconvert. Is there any way to do this compression through ffmpeg?

[jakejeffery]

also to add to that, when i do an 8.0 compression in ffmpeg it always adds the LFE flag. I'm just trying to have a true 8 channel without LFE. just FL FC FR SL SR BL BC BR

also as a note when i do pan8 in wav format it gives me LFE pan octagonal doesnt....