summaryrefslogtreecommitdiffstats
path: root/Documentation/sound/alsa/soc/pops_clicks.txt
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/sound/alsa/soc/pops_clicks.txt')
-rw-r--r--Documentation/sound/alsa/soc/pops_clicks.txt52
1 files changed, 0 insertions, 52 deletions
diff --git a/Documentation/sound/alsa/soc/pops_clicks.txt b/Documentation/sound/alsa/soc/pops_clicks.txt
deleted file mode 100644
index e1e74da..0000000
--- a/Documentation/sound/alsa/soc/pops_clicks.txt
+++ /dev/null
@@ -1,52 +0,0 @@
-Audio Pops and Clicks
-=====================
-
-Pops and clicks are unwanted audio artifacts caused by the powering up and down
-of components within the audio subsystem. This is noticeable on PCs when an
-audio module is either loaded or unloaded (at module load time the sound card is
-powered up and causes a popping noise on the speakers).
-
-Pops and clicks can be more frequent on portable systems with DAPM. This is
-because the components within the subsystem are being dynamically powered
-depending on the audio usage and this can subsequently cause a small pop or
-click every time a component power state is changed.
-
-
-Minimising Playback Pops and Clicks
-===================================
-
-Playback pops in portable audio subsystems cannot be completely eliminated
-currently, however future audio codec hardware will have better pop and click
-suppression. Pops can be reduced within playback by powering the audio
-components in a specific order. This order is different for startup and
-shutdown and follows some basic rules:-
-
- Startup Order :- DAC --> Mixers --> Output PGA --> Digital Unmute
-
- Shutdown Order :- Digital Mute --> Output PGA --> Mixers --> DAC
-
-This assumes that the codec PCM output path from the DAC is via a mixer and then
-a PGA (programmable gain amplifier) before being output to the speakers.
-
-
-Minimising Capture Pops and Clicks
-==================================
-
-Capture artifacts are somewhat easier to get rid as we can delay activating the
-ADC until all the pops have occurred. This follows similar power rules to
-playback in that components are powered in a sequence depending upon stream
-startup or shutdown.
-
- Startup Order - Input PGA --> Mixers --> ADC
-
- Shutdown Order - ADC --> Mixers --> Input PGA
-
-
-Zipper Noise
-============
-An unwanted zipper noise can occur within the audio playback or capture stream
-when a volume control is changed near its maximum gain value. The zipper noise
-is heard when the gain increase or decrease changes the mean audio signal
-amplitude too quickly. It can be minimised by enabling the zero cross setting
-for each volume control. The ZC forces the gain change to occur when the signal
-crosses the zero amplitude line.