[To be filled by O.E.M., Realtek ALC898, Blue Line In, Rear] Background noise or low volume

[Xtien]

Since I upgraded to 14.04 (actually, re-installed Ubuntu because I had new disks) sound in doesn't work at computer startup. I have to type "sudo pactl load-module module-loopback latency_msec=1" in order to get sound from my TV (blue audio plug). But then, there's a lot of crackle. I have to modify the input volume up and down, the output volume up and down, then the crackle has gone.

I can probably put the module load in some startup script, but the crackle is annoying.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: alsa-base 1.0.25+dfsg-0ubuntu4
ProcVersionSignature: Ubuntu 3.13.0-24.47-generic 3.13.9
Uname: Linux 3.13.0-24-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.2
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: christine 2930 F.... pulseaudio
 /dev/snd/controlC0: christine 2930 F.... pulseaudio
 /dev/snd/pcmC0D0c: christine 2930 F...m pulseaudio
 /dev/snd/pcmC0D0p: christine 2930 F...m pulseaudio
CurrentDesktop: Unity
Date: Sun May 25 19:08:25 2014
InstallationDate: Installed on 2014-04-21 (34 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
PackageArchitecture: all
SourcePackage: alsa-driver
Symptom: audio
Symptom_AlsaRecordingTest: ALSA recording test through plughw:SB failed
Symptom_Card: Built-in Audio - HDA ATI SB
Symptom_Jack: Blue Line In, Rear
Symptom_Type: High background noise, or volume is too low
Title: [To be filled by O.E.M., Realtek ALC898, Blue Line In, Rear] Background noise or low volume
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 11/15/2012
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 1101
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: CROSSHAIR V FORMULA-Z
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: Rev 1.xx
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr1101:bd11/15/2012:svnTobefilledbyO.E.M.:pnTobefilledbyO.E.M.:pvrTobefilledbyO.E.M.:rvnASUSTeKCOMPUTERINC.:rnCROSSHAIRVFORMULA-Z:rvrRev1.xx:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.name: To be filled by O.E.M.
dmi.product.version: To be filled by O.E.M.
dmi.sys.vendor: To be filled by O.E.M.

[Raymond (superquad-vortex2)]

any reason to use loopback when you have line playback volume ?

try turn on line playback switch and change line playback volume to 0 dB

Simple mixer control 'Line',0
  Capabilities: pvolume pswitch
  Playback channels: Front Left - Front Right
  Limits: Playback 0 - 31
  Mono:
  Front Left: Playback 28 [90%] [7.50dB] [off]
  Front Right: Playback 28 [90%] [7.50dB] [off]
Simple mixer control 'Line Boost',0
  Capabilities: volume
  Playback channels: Front Left - Front Right
  Capture channels: Front Left - Front Right
  Limits: 0 - 3
  Front Left: 0 [0%] [0.00dB]
  Front Right: 0 [0%] [0.00dB]

[Xtien (xtien)]

Loopback? I use the audio the way Ubuntu installed it for me. I havent changed anything. If it uses loopback, then the Ubuntu installer installed it that way. What do I need to change?

[Raymond (superquad-vortex2)]

alsamixer -c0

or

amixer -c0 set Line on

amixer -c0 set Line 0dB

amixer -c0 set "Line Boost" 0

[Xtien (xtien)]

line playback is on, I don't see "loopback".
Line Boost is 0, both of them.

My question was "why doesn't it stay on when rebooting my computer?"
And why is it switched off in a clean install in the first place?

[Raymond (superquad-vortex2)]

 alsactl is used to store those setting before shutdown/logout and restore after boot/login in previous version

pulseaudio only change the capture volume and boost of the input source and the playback volume of those line out/speaker/headphone

http://voices.canonical.com/david.henningsson/2012/07/13/top-five-wrong-ways-to-fix-your-audio/

you have to ask Ubuntu audio team whether alsactl is still used to save/restore those setting

do you mean sound preference did not provide (advanced option) GUI to change those controls which pulseaudio won't change ? e.g. stereo mix, playback volume of input sources, ...

control.17 {
  iface MIXER
  name 'Line Playback Volume'
  value.0 28
  value.1 28
  comment {
   access 'read write'
   type INTEGER
   count 2
   range '0 - 31'
   dbmin -3450
   dbmax 1200
   dbvalue.0 750
   dbvalue.1 750
  }
 }
 control.18 {
  iface MIXER
  name 'Line Playback Switch'
  value.0 false
  value.1 false
  comment {
   access 'read write'
   type BOOLEAN
   count 2
  }
 }

[Raymond (superquad-vortex2)]

>And why is it switched off in a clean install in the first place?

for power saving , the analog mixer is switch off by default since normal usage only need output path for playback and input path for capture

these special feature allow line in signal mix with DAC output to line out is disabled to prevent noise from line in

[Xtien (xtien)]

so, I'll probably keep doing what I did so far, like fiddling with the controls to get rid of the crackling.

[Raymond (superquad-vortex2)]

there is delay when you record your TV Audio from line in and mix and play by pulseaudio when you have a hardware mixer

[Xtien (xtien)]

Raymond, I appreciate your answers. But, quite frankly, I now have a choice of spending a few hours studying the details of how linux audio and mixers and pulseaudio work, so I can understand your answers. Or, I can hope for someone to tell me just what to do so I can get my TV audio routed through my PC with no crackling.

I am a tech person, I'm a programmer, I built my own pc, but I don't want to know how the audio works in more detail than I need to know to just make it just work :-)

[Raymond (superquad-vortex2)]

44100Hz at 1ms is 44.1 samples

it is strange that pulseaudio let you set 0.5ms which is 22.05 samples

index: 9
 driver: <module-loopback.c>
 flags: VARIABLE_RATE START_CORKED FIX_FORMAT FIX_RATE FIX_CHANNELS
 state: RUNNING
 sink: 1 <alsa_output.pci-0000_00_14.2.analog-stereo>
 volume: 0: 100% 1: 100%
         0: 0,00 dB 1: 0,00 dB
         balance 0,00
 muted: no
 current latency: 0,84 ms
 requested latency: 0,50 ms
 sample spec: s16le 2ch 44100Hz
 channel map: front-left,front-right
              Stereo
 resample method: speex-float-1
 module: 24
 properties:
  media.role = "abstract"
  module-stream-restore.id = "sink-input-by-media-role:abstract"
  media.name = "Loopback from Built-in Audio Analog Stereo"

[Launchpad Janitor (janitor)]

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