Volume Limiter

[terrence1019]

If know there has been talks of inserting a volume limiting function (a la iPod) and that the prospect of inserting it into SVN code is low.

What if I were to make a volume limiting plugin? Would that be more preferably accepted?

[Llorean]

I'm not sure I understand at all what you're proposing. How would it work? How would it offer any benefit over simply changing the volume? Or setting a pre-amp to limit the volume? Or replaygaining your files to limit maximum effective loudness?

[markun]

yes, it should be possible as a plugin as well, but since you can't do that much when the plugin is running it would not be so nice.

Would you want your limiter also to raise the volume when the music gets too quiet, or only to limit the volume during loud parts?

[dreamlayers]

I'm not sure I understand at all what you're proposing. How would it work? How would it offer any benefit over simply changing the volume? Or setting a pre-amp to limit the volume? Or replaygaining your files to limit maximum effective loudness?

Don't those scale the digital value, effectively decreasing the number of DAC bits in use, increasing distortion from that and decreasing signal to noise ratio?

I think only the volume actually scales the analog output of the DAC, allowing the full range of the DAC to be used. 

I think a volume limit option might help avoid times when while turning up the volume one overshoots into uncomfortable volume and it could help avoid volume levels which result in distortion.

[Mad Cow]

On the ipod OF, it's just a limit on how loud you can set it. So say you don't want it to go over -10db, you set it at that and the volume would never go over that. I never really understaood the point of it though.

[terrence1019]

yes, it should be possible as a plugin as well, but since you can't do that much when the plugin is running it would not be so nice.

Would you want your limiter also to raise the volume when the music gets too quiet, or only to limit the volume during loud parts?

Simply, it just limits the volume to a certain maximum limit.

Example: setting -3 db as a limit

I want it to be like iPod's volume control limit

[markun]

So you want to limit the value of the volume setting, not the actual volume itself (which also depends on the audio file being played) ? Can you explain In which cases that would be useful?

Also, I don't see how that could be done with a plugin...

[terrence1019]

So you want to limit the value of the volume setting, not the actual volume itself (which also depends on the audio file being played) ? Can you explain In which cases that would be useful?

Also, I don't see how that could be done with a plugin...

It would be useful for those who always wanted this as a setting.

But seeing it can't be done as a plugin, I'll abandon the project.

[linuxstb]

Just because a feature isn't wanted in the official Rockbox code, doesn't mean you shouldn't implement it for your own pleasure...

[saratoga]

So you want to limit the value of the volume setting, not the actual volume itself (which also depends on the audio file being played) ? Can you explain In which cases that would be useful?

Also, I don't see how that could be done with a plugin...

It would be useful for those who always wanted this as a setting.

Couldn't you just not raise the volume above whatever level you want as the limit?  Having an option who's sole purpose is to change the range of values on another option is pretty silly IMO. 

[spike66]

It is said that prolonged listening to certain volume levels can cause hearing damage. While the *recommended* max volume level is 70dB, most DAPs can go up to 100dB, so maybe it's not such a bad idea to have the option to put limits on that, just because it might be difficult to manually do it in certain occasions.  It is kind of hard sometimes to identify that limit level for instance. I personally have the tendency to “get carried away” during some songs and put the volume really loud ; it also happens when the environment is noisy, you tend to raise the volume level in order to hear the music, making your ears go through a much higher decibel level.

Apple's OF is far from perfect though, because it is not a real limit to the decibel level, but rather a "volume set limit", so e.g. if you are listening to a song at an adequate level -volume limit on- but the next song is twice as loud, you'll just hear it twice as loud… it has to be used together with replaygain I guess. They are apparently thinking of making a further change there, check http://www.allheadlinenews.com/articles/7009538792

[eevan]

I have an old Sony discman that has AVLS (automatic volume level system). It works like a limiter with a very long release time and properly adjusted threshold level. You can use the volume pot but when you reach a certain level the volume remains constant even if you crank it to the max. Also, it has very short attack time. You can turn the pot quickly to the max, but you barely notice the change in volume.

Maybe the OP had something like that in mind.

[Llorean]

Frankly this is mostly marketing fluff. How loud the audio is depends not only on what it's mastered at, but also on the sensitivity of your headphones. Many listeners also use an amp which changes things further.

There is no way to know how loud you're listening from the player's side. All you can do is replaygain your music, then attempt to choose a level you feel is comfortable with your headphones, or take careful measurement with them. Then, never turn the volume above this level.

A volume limiting plugin would be misleading since it can't be any more precise than a user simply choosing not to turn up the volume. The only way it could be effective is if it weren't controllable by a user and were capped at an extremely cautious level. Any user who can say "It's too loud to hear my music here so I'll turn it up" can also say "It's too loud to hear my music here, so I'll turn off the limit, just for a little while, so I can turn it up." You aren't taking that choice out of their hands, so it really offers no protection beyond their own decisions.

And even then, as I've said a few times now, an equalizer precut serves this exact purpose anyway (limiting the effective maximum volume).

[soap]

A method to prevent hearing damage would have to limit decibels to your eardrum.  The power delivered by your DAP's amp is just one part of the equation which determines this value.

In theory your DAP could monitor the energy level of the final signal before it enters the amplifier, and decrease the volume if found to be over a user-set limit - but here is where it gets tricky. 
What I just described limits the electrical energy leaving the DAP - but this has a relatively weak relationship to the mechanical energy delivered to your eardrums.

The efficiency of your headphones is a large factor (as Llorean mentioned) but also the physical fit of the headphones to your ear, and the nature of the air gap between (volume, shape, freedom of movement) the headphone drivers and your eardrum is also a very significant factor.  This is why your would be unable to create a lookup table for headphones and say "Headphones A deliver X decibels of energy to my eardrums when given Y watts of electrical power."
Unless you have a decently accurate model of your head, your ear canal, and your outer ear you simply can not solve this equation to a level of confidence which would deliver safety.

I'm not sure I understand at all what you're proposing. How would it work? How would it offer any benefit over simply changing the volume? Or setting a pre-amp to limit the volume? Or replaygaining your files to limit maximum effective loudness?

Don't those scale the digital value, effectively decreasing the number of DAC bits in use, increasing distortion from that and decreasing signal to noise ratio?

Decreasing the digital value does decrease the number of bits in use, but does not increase distortion - simply decreases the signal to noise ratio.  And considering you only want to deliver 70-80 decibels to your ear, and the background noise of a quiet room is 20 or so.....

[saratoga]

It is said that prolonged listening to certain volume levels can cause hearing damage. While the *recommended* max volume level is 70dB, most DAPs can go up to 100dB, so maybe it's not such a bad idea to have the option to put limits on that, just because it might be difficult to manually do it in certain occasions. 

Its not actually possible to limit the dB at your ear, since that depends on the headphones used.  The most you can do is limit the power at the amp, and we have that already (volume control).