version: 4.3.1,

Input: 2 mp3 files,

the chennels mp3: 1,

the sampling: 8000

ffmpeg version 4.3.1 Copyright (c) 2000-2020 the FFmpeg developers

built with gcc 4.8.5 (GCC) 20150623 (Red Hat 4.8.5-39) configuration: --disable-debug --enable-libx264 --enable-libx265 --enable-gpl --enable-shared --prefix=/usr/local/ffmpeg libavutil 56. 51.100 / 56. 51.100 libavcodec 58. 91.100 / 58. 91.100 libavformat 58. 45.100 / 58. 45.100 libavdevice 58. 10.100 / 58. 10.100 libavfilter 7. 85.100 / 7. 85.100 libswscale 5. 7.100 / 5. 7.100 libswresample 3. 7.100 / 3. 7.100 libpostproc 55. 7.100 / 55. 7.100 Hyper fast Audio and Video encoder usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...