1 =====================
2 Audio Pops and Clicks
3 =====================
4
5 Pops and clicks are unwanted audio artifacts c
6 of components within the audio subsystem. This
7 audio module is either loaded or unloaded (at
8 powered up and causes a popping noise on the s
9
10 Pops and clicks can be more frequent on portab
11 because the components within the subsystem ar
12 depending on the audio usage and this can subs
13 click every time a component power state is ch
14
15
16 Minimising Playback Pops and Clicks
17 ===================================
18
19 Playback pops in portable audio subsystems can
20 currently, however future audio codec hardware
21 suppression. Pops can be reduced within playb
22 components in a specific order. This order is
23 shutdown and follows some basic rules:-
24 ::
25
26 Startup Order :- DAC --> Mixers --> Output
27
28 Shutdown Order :- Digital Mute --> Output P
29
30 This assumes that the codec PCM output path fr
31 a PGA (programmable gain amplifier) before bei
32
33
34 Minimising Capture Pops and Clicks
35 ==================================
36
37 Capture artifacts are somewhat easier to get r
38 ADC until all the pops have occurred. This fol
39 playback in that components are powered in a s
40 startup or shutdown.
41 ::
42
43 Startup Order - Input PGA --> Mixers --> AD
44
45 Shutdown Order - ADC --> Mixers --> Input P
46
47
48 Zipper Noise
49 ============
50 An unwanted zipper noise can occur within the
51 when a volume control is changed near its maxi
52 is heard when the gain increase or decrease ch
53 amplitude too quickly. It can be minimised by
54 for each volume control. The ZC forces the gai
55 crosses the zero amplitude line.
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