sound/soc/pops-clicks.rst

2 Audio Pops and Clicks
5 Pops and clicks are unwanted audio artifacts caused by the powering up and down
6 of components within the audio subsystem. This is noticeable on PCs when an
7 audio module is either loaded or unloaded (at module load time the sound card is
11 because the components within the subsystem are being dynamically powered
12 depending on the audio usage and this can subsequently cause a small pop or
19 Playback pops in portable audio subsystems cannot be completely eliminated
20 currently, however future audio codec hardware will have better pop and click
21 suppression.  Pops can be reduced within playback by powering the audio
23 shutdown and follows some basic rules:-
26    Startup Order :- DAC --> Mixers --> Output PGA --> Digital Unmute
28    Shutdown Order :- Digital Mute --> Output PGA --> Mixers --> DAC
43    Startup Order - Input PGA --> Mixers --> ADC
45    Shutdown Order - ADC --> Mixers --> Input PGA
50 An unwanted zipper noise can occur within the audio playback or capture stream
52 is heard when the gain increase or decrease changes the mean audio signal