They are both very similar, in fact they are both automatic volume control. In fact, if your processor is powerful enough, you can easily do an AGC with a DRC (depends on the number of bands of DRC and the flexilbility of the gain threshold).
I would say that the DRC and AGC are different names used in different applications. DRC is more commonly used and it is usually seen in DVD player settings to enable "night listening mode". It basically compresses loud signals so that when the end-user is watching a movie at night, the loud explosions will not wake the entire neighbourhood! Typically the softer signals are not altered, they are increased linearly by increasing the overall volume of the DVD player.
AGC is a a new term to describe the operation of our TPA2016 in portable devices like cellphones and GPS. The idea is very much the same, except that you are more interested in boosting the level of the softer signals to make the overall audio louder. THis is especially useful in music playback in cellphones and navigation directions in GPS where such small speakers have a hard time overcoming high ambient noise (eg. in a car, bus or train).
Note that we avoid clipping distortion in both DRC and AGC.
Below are more info and definitions of the 2 terms.
Dynamic range compression, also called DRC or simply compression, is a process that reduces the dynamic range of an audio signal. In simple terms, a compressor is an automatic volume control. Loud sounds over a certain threshold are reduced in level while quiet sounds remain untreated (this is known as downward compression, while the less common upward compression involves making sounds below the threshold louder while the louder passages remain unchanged).
AGC is Automatic Gain Control and is currently implemented only our TPA2016 amplifier.
