Unity Float to db

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hi! As you all know, i hope, Unity has a function where you can read the ... let's call it "volume" of every sample of an audio file. the problem is: its given in float -1 to +1. I found some sites where they convert float to db. But only 0 to +1 floats. what to do with negative floats? Is there any "unity-compatible" conversion from float to db?

Answer 1

Answer by Bunny83 · May 10, 2015 at 02:22 PM

The data you get from Unity are PCM samples which are by nature positive and negative. In a wave file they are stored as an unsigned integer but represent the same information, just shifted into the positive range (like xortrox mentioned above).

Not sure why you want it in decibel but the conversion for volume is usually:

 float db = 20f * Mathf.Log10(amplidude);

amplitude should be between 0 and 1. You get that by taking the absolute value of each sample (Mathf.Abs()).

Note that decibel is just a relation compared to a reference value. Depending on the usage a db value could mean totally different things. See Decibel.

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Kokujou · May 10, 2015 at 02:26 PM 0

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so its really this simple huh... okay than i'll try this maybe it works this time ^_^ i'm trying to create a script that builds a road via an audio file like that game "Audiosurf" does...

Bunny83 · May 10, 2015 at 02:30 PM 0

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Keep in mind that you probably want to take the average of a period and not a single sample.

Kokujou · May 10, 2015 at 02:35 PM 0

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yeah i got this in my mind... still... it's so complicated to copy audiosurf... i mean just to build a road with curves is... nearly impossible.. >.<

Bunny83 · May 10, 2015 at 02:46 PM 0

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Well, how you actually approach this? I never played audiosurf (but i've seen it). If the track is actually derived from the audio you probably want to measure the average volume in equal intervals and use the derivative (change between two measured levels) as indication if the track should go up or down.

Kokujou · May 10, 2015 at 02:48 PM 0

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maybe... well but a short trip back to the db Problem... i analyzed an audio file with unity... but the samples where NOTHING is playing so ... a pause. is -6db. while other stuff is -7db... -11db... what the hell is going on there...

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Answer 2

Answer by Catlard · May 10, 2015 at 02:09 PM

I think you're misunderstanding the meaning of "float". A float is a kind of number the computer recognizes that takes up a certain amount of memory in the computer, where as db is just a name for the number. I assume that however they measure the decibels in an audio file at one time, it is stored either as a float, or something else that can handle decimals. The name of a VARIABLE is probably db, but the variable is an object the computer calls a "float". Does that make sense?

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Kokujou · May 10, 2015 at 02:15 PM 0

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however the assigned range, unity gives is from -1 to +1. thats definitly not the value in db! maybe its a factor or something i don't know. whether or not i need a conversion from the unity values into db values!

Catlard · May 10, 2015 at 02:19 PM 0

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Does it matter what they've done to the values, as long as you can convert them back to the same range using algebra? Clearly 0 must correspond to -1 in this situation, right?

Also, I have seen some decibel values on stereos as negative numbers. Just saying.

http://www.animations.physics.unsw.edu.au/jw/images/dB_files/LI.gif

Kokujou · May 10, 2015 at 02:21 PM 0

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i don't know thats why i'm asking! there must be a reason why unity is using negative numbers. if they just want a higher range they could've taken 0 to +2 but why -1 to +1?

Unity Float to db

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