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Topic: Apply frequency equalization to MP3? (Read 1247 times) previous topic - next topic - Topic derived from Amplifying MP3's
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Apply frequency equalization to MP3?

And, is there a way to apply frequency equalization to the MP3 without decoding and re-encoding it? Can mp3DirectCut do that?

Re: Apply frequency equalization to MP3?

Reply #1 –
I don't know of any software that does that.

It should be possible since MP3 uses FFT.

Re: Apply frequency equalization to MP3?

Reply #2 –
https://hydrogenaud.io/index.php/topic,65556.0.html

Quote from: SebastianG on
The short answer to this is: No.

Long answer: There's no tool out there I know of that does this kind of job. You could try to code one that messes with scale factors for equalizing or "simply" set some MDCT samples to zero. The downside however is that "aliasing cancellation" won't work anymore. The problem is that the filterbank is critically sampled. The same is actually true for volume fades that some tools offer (some temporal aliasing will stay).

Re: Apply frequency equalization to MP3?

Reply #3 –
Quote from: lvqcl on
https://hydrogenaud.io/index.php/topic,65556.0.html

Quote from: SebastianG on
The short answer to this is: No.

Long answer: There's no tool out there I know of that does this kind of job. You could try to code one that messes with scale factors for equalizing or "simply" set some MDCT samples to zero. The downside however is that "aliasing cancellation" won't work anymore. The problem is that the filterbank is critically sampled. The same is actually true for volume fades that some tools offer (some temporal aliasing will stay).
A colleague of mine did this with MP2 files that were recorded from CDs with de-emphasis switched on, even though it was supposed to be off. His software was based on a partial decoder I wrote in the 90s that could read the scale factors to display a kind of volume indicator. But only MP2, I don't know how similar it is to MP3.

Re: Apply frequency equalization to MP3?

Reply #4 –
I remember that one of the MP3 decoders that Winamp once had, applied the equalizer directly to the scalefactors. This was done basically as a fast way to do EQ, not as a way to have good quality. Later on they implemented a standard equalizer and one could switch between the fast and the good one. 
And finally, they ditched the decoder for a better quality one (although people were switching to third party ones already, like the mad decoder)

So, equalizing the raw data is possible, but I don't know of any tool that is designed to do so.