Hi David,
On 03/31/2015 01:43 PM, David Henningsson wrote:
On 2015-03-31 12:06, Nikita N. wrote:
If you have any concrete examples (alsa-info please!) of speakers that can be burned out, and you know a maximum speaker volume where this
As we said, that is not our bug, we are not audio experts, nor any of us is interested in audio matters.
Here's my suggestion how to move forward on this:
- Gather consensus that limit the maximum volume on internal
speakers is the right way forward. Takashi, Clemens, anyone against that strategy?
- From the person with the hardware, we will need alsa-info (
https://wiki.ubuntu.com/Audio/AlsaInfo ), and also the max volume where this does not happen. Is -6 dB good enough? -12 dB? I don't know - this is something someone with the hardware must tell us, it cannot simply be guessed.
- I or someone else can write a kernel patch that limits the maximum
volume of the speakers to the amount deducted from point 2). Considering that we're actually dealing with hardware breakage, this should be sent to stable as well. Then no userspace application can set the volume higher than our limit.
Probably a kernel patch is not necessary. asound.conf ans asound.state can do similar job. If the master volume is fixed to a safe value, the audio can be routed through softvol plugin, which can be used as a replacement for the master volume control (the exact levels need to be confirmed with someone who has access to the problematic hardware).
state.Intel { control.1 { comment.access 'read' // read-only comment.type INTEGER comment.count 2 comment.range '0 - 64' comment.dbmin -6400 comment.dbmax 0 iface MIXER name 'Speaker Playback Volume' value.0 42 // safe volume levels value.1 42 // } }
Could be even better if the HW master volume control is hidden (I don't know how to do this), and the softvol control is exposes as master volume:
pcm.!default { type softvol slave.pcm "default" control.name "Master Volume" control.card 0 }
...something like this.
Kind regards, Nikolay