результат ffmpeg ниже.
ffmpeg version git-2020-05-28-c0f01ea Copyright (c) 2000-2020 the FFmpeg developers
built with gcc 9.3.1 (GCC) 20200523
configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libsrt --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --disable-w32threads --enable-libmfx --enable-ffnvcodec --enable-cuda-llvm --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf
libavutil 56. 49.100 / 56. 49.100
libavcodec 58. 89.100 / 58. 89.100
libavformat 58. 43.100 / 58. 43.100
libavdevice 58. 9.103 / 58. 9.103
libavfilter 7. 83.100 / 7. 83.100
libswscale 5. 6.101 / 5. 6.101
libswresample 3. 6.100 / 3. 6.100
libpostproc 55. 6.100 / 55. 6.100
Input #0, wav, from '1.wav':
Duration: 00:06:17.50, bitrate: 63 kb/s
Stream #0:0: Audio: mp3 (U[0][0][0] / 0x0055), 44100 Hz, mono, fltp, 64 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (mp3 (mp3float) -> mp3 (mp3_mf))
Press [q] to stop, [?] for help
[mp3_mf @ 000002e13cca9100] MFT name: 'MP3 Encoder ACM Wrapper MFT'
Output #0, mp3, to 'out.mp3':
Metadata:
TSSE : Lavf58.43.100
Stream #0:0: Audio: mp3 (mp3_mf), 44100 Hz, mono, s16, 128 kb/s
Metadata:
encoder : Lavc58.89.100 mp3_mf
size= 2816kB time=00:03:14.50 bitrate= 118.6kbits/s speed= 388x
size= 5887kB time=00:06:17.54 bitrate= 127.7kbits/s speed= 393x
video:0kB audio:5886kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.007665%