Automatically control volume of songs in playlist to make a better experience.

Pros: Lower input dynamic range required by peak detector; Inherently higher linearity

Cons: Instabilities with high compression or expansion; Higher settling-time

• looper filter: generate VGA parameter
• peak detector: detect amplitude level of Vout
• log conv: make AGC a linear system in decibels

Pros: No instability problems; Ideally zero settling-time

Cons: AGC input dynamic range required by peak detector; High linearity required in loop

for ((i=1;i<10;i++)); do
    ffmpeg -i raw/${i}.mp3 -acodec pcm_f32le -ac 1 -ar 44100 input/${i}.wav;
done

python3 agc.py # -> output/*.wav

Perez, Automatic Gain Control http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CEEQFjAD&url=http://www.springer.com/cda/content/document/cda_downloaddocument/9781461401667-c2.pdf?SGWID=0-0-45-1180039-p174121673&ei=LtcQU7McgrXgBMTdgdAI&usg=AFQjCNHUReiMDeUPA-hpYoerCXiPZLvXZg&sig2=j5UA1xMWoB-qjdelhsDpLQ&bvm=bv.62286460,d.bGE&cad=rja

TI: Software Implementation of Automatic Gain Controller for Speech Signal http://www.ti.com/lit/wp/spraal1/spraal1.pdf

Automatic gain control https://en.wikipedia.org/wiki/Automatic_gain_control

Python AGC of audio time-freq Demo https://github.com/jorgehatccrma/pyagc

Adaptive volume normalization on a stream of PCM data https://dsp.stackexchange.com/questions/24335/adaptive-volume-normalization-on-a-stream-of-pcm-data

Adaptive Gain Control with the Least Mean Squares Algorithm https://www.allaboutcircuits.com/technical-articles/adaptive-gain-control-with-the-least-mean-squares-algorithm/

Adaptive Volume Rendering using Fuzzy Logic Control http://web.cse.ohio-state.edu/~shen.94/papers//Li2001.pdf

Automatic Loudness Control https://www.acoustics.asn.au/conference_proceedings/ICA2010/cdrom-ICA2010/papers/p960.pdf

StreamingKit https://github.com/tumtumtum/StreamingKit

iOS AVAudioEngine http://www.jianshu.com/p/506c62183763

Audio API Overview https://www.objc.io/issues/24-audio/audio-api-overview/

Understanding Automatic Gain Control https://www.allaboutcircuits.com/technical-articles/understanding-automatic-gain-control/

tf_agc - Time-frequency Automatic Gain Control https://labrosa.ee.columbia.edu/matlab/tf_agc/

Youtube: Automatic Volume Level Control circuit demonstration | scanner https://www.youtube.com/watch?v=pUii_pDQxg8

Math Plot: http://fooplot.com/#W3sidHlwZSI6MCwiZXEiOiItMy8yKngtNyIsImNvbG9yIjoiIzAwMDAwMCJ9LHsidHlwZSI6MTAwMCwid2luZG93IjpbIi0yNDIuNjgzODY5NDAwMDI0MjYiLCIyNDEuNjAzODY5NDAwMDI0MjgiLCItMTUwLjk5MTYxMTkzODQ3NjUyIiwiMTQ3LjAzMTYxMTkzODQ3NjUiXX1d