AMR Optimization

针对AMR语音特性，通过ffmpeg参数实现语音体验优化，评分基于NISQA

[ FFmpeg Pipeline ]

> ffmpeg -y -i input.wav \
  -af "highpass=f=310:poles=2,lowpass=f=3720:poles=2, \
       equalizer=f=3150:width_type=h:width=1000:g=7.5, \
       loudnorm=I=-18.5:TP=-1.5:LRA=6,aresample=8000" \
  -ar 8000 -ab 12.2k -ac 1 output.amr

[ Audio Samples ]