From: Takashi Iwai Date: Thu, 10 Nov 2016 21:23:58 +0000 (+0100) Subject: ASoC: doc: ReSTize pops_clicks.txt X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=c9746eeafca3b5286a0355b895eb48af19d54d2d;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git ASoC: doc: ReSTize pops_clicks.txt A simple conversion from a plain text file. The file name was changed from "pops_clicks" to "pops-clicks" to align with others. Acked-by: Mark Brown Signed-off-by: Takashi Iwai --- diff --git a/Documentation/sound/alsa/soc/pops_clicks.txt b/Documentation/sound/alsa/soc/pops_clicks.txt deleted file mode 100644 index e1e74daa4497..000000000000 --- 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. diff --git a/Documentation/sound/soc/index.rst b/Documentation/sound/soc/index.rst index 4ac3585e7dd1..4dd679927a91 100644 --- a/Documentation/sound/soc/index.rst +++ b/Documentation/sound/soc/index.rst @@ -13,3 +13,4 @@ The documentation is spilt into the following sections:- dapm platform machine + pops-clicks diff --git a/Documentation/sound/soc/pops-clicks.rst b/Documentation/sound/soc/pops-clicks.rst new file mode 100644 index 000000000000..de7eb2a6604a --- /dev/null +++ b/Documentation/sound/soc/pops-clicks.rst @@ -0,0 +1,55 @@ +===================== +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.