Help Needed: Writing Fade In/Out Function for Volume Control

In summary, the volume control will fade in and out over time according to a power-law decay curve, with an initial volume at time t=0 and a final volume at time t=T.
  • #1
VMail
11
0
This more of a maths question rather than a physics one, but I do remember doing something similar is my physics course.

Basically I trying to write a fade in and fade out function
for a volume control but I am stuck on the maths part. Thats where I
need you.

I've tryed a linear fade, but that does not sound good

so y = volume (0-100)
and x = time (0.5)

time is fixed to 0.5sec but can alter slightly if needed

volume will be one value from 0 to 100, but I don't know what the
volume will be until the function is needed
 
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  • #2
Just putting this PM here because I can't read the formula in the PM

Ambitwistor said:
If a linear scaling doesn't sound good, you might try something that scales as a power of time other than 1. That is, something like [itex]t^{-\alpha}[/itex] for some [itex]\alpha>0[/itex] ([itex]\alpha\neq 1[/itex]). It will fade faster than linear for [itex]\alpha>1[/itex], and slower than linear for [itex]0<\alpha<1[/itex].

However, you can't just use a straight power law, because it goes to infinity at t=0, and never drops completely to zero. So, you want a power law that's shifted to the left a bit (to be positive at t=0), and also down a bit (to drop to zero at finite t).

So, you want a volume function that looks something like this,

[tex]V(t) = A(t+t_0)^{-\alpha} + B[/itex]

for some constants A, B, and [itex]t_0[/itex].

Adding the constraints that you want the volume to have some initial volume at time t=0 ([itex]V(0) = V_0[/itex]), and drop to zero volume after some finite time t=T ([itex]V(T) = 0[/itex]), that leads to a volume function that fades with time like this,

[tex]V(t) = \frac{1-(\frac{1+T/t_0}{1+t/t_0})^\alpha}{1-(1+T/t_0)^\alpha} V_0[/tex]

or,

[tex]V(t) = \frac{1-k/(1+t/t_0)^\alpha}{1-k} V_0[/tex]

where [itex]k = (1+T/t_0)^\alpha[/itex] -- assuming I haven't screwed up the algebra; you'll have to check it.

You'll have to play around with the parameters [itex]\alpha[/itex] and [itex]t_0[/itex] to find something that sounds good. I already mentioned the effect that [itex]\alpha[/itex] has on the fade; larger [itex]t_0[/itex] values will also make for a slower fade (getting out on the tail end of the power-law decay curve).
 
  • #3
ok, I'm using

to=0 to 475 (stepping by 25)
and alpha as 1.01
Vo is set at 50

The values that I am getting are 16-45(rounded up)
is this correct?
 

Related to Help Needed: Writing Fade In/Out Function for Volume Control

1. How does a fade in/out function for volume control work?

The fade in/out function for volume control gradually increases or decreases the volume over a specified period of time. This is achieved by adjusting the volume levels at regular intervals until the desired volume is reached.

2. What is the purpose of a fade in/out function for volume control?

The purpose of a fade in/out function for volume control is to create a smooth and gradual change in volume instead of an abrupt change. This can be useful in audio or video applications to avoid sudden changes in volume that may be jarring to the listener.

3. What factors should be considered when implementing a fade in/out function for volume control?

When implementing a fade in/out function for volume control, factors such as the duration of the fade, the starting and ending volume levels, and the intervals at which the volume is adjusted should be considered. Additionally, the type of audio or video being used may also affect the implementation.

4. Are there any potential drawbacks to using a fade in/out function for volume control?

One potential drawback is that the fade in/out function may add extra processing time and may not be suitable for real-time applications. Additionally, if the fade is too long, it may be perceived as too slow or unnecessary by the user.

5. How can a fade in/out function for volume control be implemented in code?

The specific implementation of a fade in/out function for volume control may vary depending on the programming language and platform being used. Generally, it involves using a loop to adjust the volume at regular intervals until the desired volume is reached. Some programming languages may have built-in functions or libraries to help with this task.

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