** Summary changed: - MicBoost with HDA-Intel introduces DC-bias + [intrepid] MicBoost with Intel HDA / Realtek ALC882 introduces DC-bias
** Description changed: - Running Ubuntu Intrepid with Intel-HDA (ALC882) sound: MicBoost does - not seem to work properly. + Intrepid with Intel-HDA (ALC882) sound: MicBoost does not seem to work + properly. Background: ====== Prior to seeing symptoms (below), have never been able to get microphone to work well for Skype: - mic audio very low with 0 MicBoost (0 setting in alsamixer and gnomealsamixer). - mic audio completely distorted and nearly inaudible with full MicBoost. - intermediate MicBoost caused distortion but audible. - Skype setting "let Skype adjust audio..." caused mic audio to be distorted and inaudible (so did not use). Always assumed problem with Skype was some problem with pulseaudio until I tried recording from Audacity and noticed that adjusting MicBoost while recording from microphone shows four steps of DC-Offset (0 - 3). (see attached screenshot). Problem: ====== According to the screenshot, MicBoost seems to be amplifying the microphone (good), but also creating an extreme negative DC-bias (bad), i.e. shifting the signal into the negative until only the largest positive peaks are not clipped. Each step in the audio signal in the audacity screenshot corresponds to one of the four steps of the MicBoost control. Audacity has same result with Recording Device ID 0 (OSS: /dev/dsp) and Device ID 2 (ALSA: HDA Intel: ALC882 Analog (hw:0,0)). (will attach the Audacity Device Info output next) Examining the output of the alsa-info.sh script: http://www.alsa-project.org/db/?f=386a234a728c1b20f88f717d7839651e6938f7aa shows control.17 of the AlsaCtl section: control.17 { comment.access 'read write' comment.type INTEGER comment.count 2 comment.range '0 - 3' comment.dbmin 0 comment.dbmax 3000 iface MIXER name 'Mic Boost' value.0 2 value.1 2 } This is a total SWAG, but one possibility comes to mind: Could the type INTEGER be wrong? Perhaps it should be a FLOAT and we are seeing the results of an aliased setting? If someone can point me in the right direction, I would be willing to look at the source to try and track it down. I know C/C++/Java, but I have no idea where it might be in the source (i.e. kernel?, module?, driver?). Where do I find the definition and use of the Control.17 configuration above? -- [intrepid] MicBoost with Intel HDA / Realtek ALC882 introduces DC-bias https://bugs.launchpad.net/bugs/316165 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
