How to remove ALL metadata using ffmpeg?

Question

I have input file: infile.mp3
This file contains metadata (artist, genre, etc.)
I try remove all metadata to output a .wav file.

Yes! I found option:

-map_metadata -1

But output is unexpected to me...

$ ffmpeg -i infile.mp3 -acodec pcm_s16le -ac 2 \
                -ar 44100 -map_metadata -1 ./outfile.wav

OK!

$ ffprobe outfile.wav
Input #0, wav, from 'inp.wav':
  Metadata:
    encoder         : Lavf56.25.101
  Duration: 00:04:00.47, bitrate: 1411 kb/s
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 2 channels, s16, 1411 kb/s

You see? encoder metadata exists!

And in the wav header after "subchunk1_id" with "fmt " value I expect in "subchunk2_id" is the "data" value (clear expected example):

$ strings outfile.wav | more
RIFFFB
WAVEfmt
data

But it is not (LIST, INFOISFT, etc):

$ strings outfile.wav | more
RIFFFB
WAVEfmt 
LIST
INFOISFT
Lavf56.25.101
data

Well.. How to really remove all metadata from the output file?

Solution

-fflags +bitexact -flags:v +bitexact -flags:a +bitexact