Is it possible for ffmpeg to select audio channels without reencoding

Question

I use this command to try and downmix an audio file without re-encoding but the channel selection is not done :

$ time ffmpeg -i input.aac -c:a copy -map_channel 0.0.0 -map_channel 0.0.0 output.aac -y
[aac @ 0x5655577ffcc0] Estimating duration from bitrate, this may be inaccurate
Input #0, aac, from 'input.aac':
  Duration: 01:32:25.17, bitrate: 122 kb/s
    Stream #0:0: Audio: aac (LC), 44100 Hz, stereo, fltp, 122 kb/s
Output #0, adts, to 'output.aac':
  Metadata:
    encoder         : Lavf58.20.100
    Stream #0:0: Audio: aac (LC), 44100 Hz, stereo, fltp, 122 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
size=   82790kB time=01:54:51.61 bitrate=  98.4kbits/s speed= 973x    
video:0kB audio:82790kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000000%

real    0m7.302s
user    0m7.068s
sys 0m0.216s

Can you help ?

Answer 1

Not possible. -map_channel invokes the pan filter behind the scenes.