Here is one of my many other attempts. It should be clear that I am a
beginner with ffmpeg.
No matter what I try, ffmpeg seems to merge all the 32 USB channels into 6.
For example:
ffmpeg -ac 2 -c ac3 -loglevel debug -f avfoundation -i :2 -af 'pan=5.1'
output.wav
Part of the output:
Splitting the commandline.
Reading option '-ac' ... matched as option 'ac' (set number of audio
channels) with argument '2'.
Reading option '-c' ... matched as option 'c' (codec name) with argument
'ac3'.
Reading option '-loglevel' ... matched as option 'loglevel' (set logging
level) with argument 'debug'.
Reading option '-f' ... matched as option 'f' (force format) with
argument 'avfoundation'.
Reading option '-i' ... matched as input url with argument ':2'.
Reading option '-af' ... matched as option 'af' (set audio filters) with
argument 'pan=5.1'.
Reading option 'output.wav' ... matched as output url.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option loglevel (set logging level) with argument debug.
Successfully parsed a group of options.
Parsing a group of options: input url :2.
Applying option ac (set number of audio channels) with argument 2.
Applying option c (codec name) with argument ac3.
Applying option f (force format) with argument avfoundation.
Successfully parsed a group of options.
Opening an input file: :2.
[avfoundation @ 0x7f96400041c0] audio device 'Digiface USB (24162724)'
opened
For transform of length 128, inverse, mdct_float, flags: [aligned,
out_of_place], found 3 matches:
1: mdct_inv_float_avx2 - type: mdct_float, len: [16, ∞],
factors[2]: [2, any], flags: [aligned, out_of_place, inv_only], prio: 544
2: mdct_inv_float_c - type: mdct_float, len: [2, ∞], factors[2]:
[2, any], flags: [unaligned, out_of_place, inv_only], prio: 96
3: mdct_naive_inv_float_c - type: mdct_float, len: [2, ∞],
factors[2]: [2, any], flags: [unaligned, out_of_place, inv_only], prio:
-130976
For transform of length 64, inverse, fft_float, flags: [aligned,
inplace, preshuf, asm_call], found 3 matches:
1: fft_sr_asm_float_avx2 - type: fft_float, len: [64, 131072],
factor: 2, flags: [aligned, inplace, out_of_place, preshuf, asm_call],
prio: 480
2: fft_sr_asm_float_fma3 - type: fft_float, len: [64, 131072],
factor: 2, flags: [aligned, inplace, out_of_place, preshuf, asm_call],
prio: 448
3: fft_sr_asm_float_avx - type: fft_float, len: [64, 131072],
factor: 2, flags: [aligned, inplace, out_of_place, preshuf, asm_call],
prio: 416
Transform tree:
mdct_inv_float_avx2 - type: mdct_float, len: 128, factors[2]: [2,
any], flags: [aligned, out_of_place, inv_only]
fft_sr_asm_float_avx2 - type: fft_float, len: 64, factor: 2,
flags: [aligned, inplace, out_of_place, preshuf, asm_call]
For transform of length 256, inverse, mdct_float, flags: [aligned,
out_of_place], found 3 matches:
1: mdct_inv_float_avx2 - type: mdct_float, len: [16, ∞],
factors[2]: [2, any], flags: [aligned, out_of_place, inv_only], prio: 544
2: mdct_inv_float_c - type: mdct_float, len: [2, ∞], factors[2]:
[2, any], flags: [unaligned, out_of_place, inv_only], prio: 96
3: mdct_naive_inv_float_c - type: mdct_float, len: [2, ∞],
factors[2]: [2, any], flags: [unaligned, out_of_place, inv_only], prio:
-130976
For transform of length 128, inverse, fft_float, flags: [aligned,
inplace, preshuf, asm_call], found 3 matches:
1: fft_sr_asm_float_avx2 - type: fft_float, len: [64, 131072],
factor: 2, flags: [aligned, inplace, out_of_place, preshuf, asm_call],
prio: 480
2: fft_sr_asm_float_fma3 - type: fft_float, len: [64, 131072],
factor: 2, flags: [aligned, inplace, out_of_place, preshuf, asm_call],
prio: 448
3: fft_sr_asm_float_avx - type: fft_float, len: [64, 131072],
factor: 2, flags: [aligned, inplace, out_of_place, preshuf, asm_call],
prio: 416
Transform tree:
mdct_inv_float_avx2 - type: mdct_float, len: 256, factors[2]: [2,
any], flags: [aligned, out_of_place, inv_only]
fft_sr_asm_float_avx2 - type: fft_float, len: 128, factor: 2,
flags: [aligned, inplace, out_of_place, preshuf, asm_call]
[avfoundation @ 0x7f96400041c0] All info found
Input #0, avfoundation, from ':2':
Duration: N/A, start: 1307454.032041, bitrate: N/A
Stream #0:0, 1, 1/100: Audio: ac3, 44100 Hz, 32 channels, fltp
Successfully opened the file.
Parsing a group of options: output url output.wav.
Applying option af (set audio filters) with argument pan=5.1.
Successfully parsed a group of options.
Opening an output file: output.wav.
File 'output.wav' already exists. Overwrite? [y/N] y
[file @ 0x7f9640108000] Setting default whitelist 'file,crypto,data'
Successfully opened the file.
For transform of length 128, inverse, mdct_float, flags: [aligned,
out_of_place], found 3 matches:
1: mdct_inv_float_avx2 - type: mdct_float, len: [16, ∞],
factors[2]: [2, any], flags: [aligned, out_of_place, inv_only], prio: 544
2: mdct_inv_float_c - type: mdct_float, len:
