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"Fix" mp3?
eiko
post Mar 20 2009, 05:43
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Is there any app to take an mp3, or a WAV that was previously compressed to mp3, and add high frequency sounds in plausible locations that mp3 encoding would have removed?

Thanks

This post has been edited by eiko: Mar 20 2009, 05:43
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timcupery
post Mar 20 2009, 06:07
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Before we talk about applications to do what you want, let's figure out what you're looking for first - what you want to accomplish, and whether anything can do it, and what comes closest.
I assume you're talking about dithering. This basically adds noise to an audio stream, and as such fills in higher frequencies that may have been lowpassed out through encoding. However, this won't fill in the frequencies that were lost upon lowpassing.

If your goal is to take lossy material and make it sound less lossy, you're mostly out of luck.

But I may be misreading your intent. What are you hoping to accomplish?


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eiko
post Mar 20 2009, 06:39
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Hmmm, I'm interested in converting some mp3s to WAV files and making it tough to detect they were originally encoded in mp3.

I know I can just add a small low and high frequency noise and those "true audio" programs fail pass it off as high quality audio. And people can't really hear the difference. The only problem remaining is that it's quite obvious what was done from looking at the spectrum view of the track.

So I'm wondering if there's any program or strategy that would fix that up a little by adding "plausible" noise.
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Axon
post Mar 20 2009, 06:43
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It's called SBR. I don't think it works for existing MP3s. Even when it does work (MP3PRO) it only does miracles at very low bitrates.
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Iain
post Mar 20 2009, 07:07
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QUOTE (eiko @ Mar 19 2009, 20:43) *
Is there any app to take an mp3, or a WAV that was previously compressed to mp3, and add high frequency sounds in plausible locations that mp3 encoding would have removed?

Thanks



If you want to add high frequencies to compensate for a low pass filter, then you may want to look at an enhancer or Exciter. Specifically, an harmonic exciter like the Aphex Aural Exciter. These devices add additional high frequency harmonics to give a sense of increased clarity.

They work something like this.

1)Apply a high pass filter to original signal
2)Distort high frequencies to create additional harmonic content
3)Mix with original signal.
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timcupery
post Mar 21 2009, 02:39
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are you trying to fool someone here? it sounds like you're aware that this won't make any difference in sound, but may look different on a spectral analysis display or to a program that's supposed to judge if something is sourced from mp3 or cd.


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eiko
post Mar 21 2009, 04:38
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Yep. It's for a noble cause. wink.gif

Will check into these ideas thanks.
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rpp3po
post Mar 21 2009, 11:02
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QUOTE (eiko @ Mar 21 2009, 04:38) *
Yep. It's for a noble cause. wink.gif

Will check into these ideas thanks.


I see only two options here:

1.) He is a pirate of the lowest sort, who wants to share pseudo lossless files to be allowed to download other peoples' content.

2.) He's from an organization planning to demoralize the lossless sharing scene by injecting pseudo lossless files.

This post has been edited by rpp3po: Mar 21 2009, 11:19
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M
post Mar 21 2009, 18:40
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QUOTE (rpp3po @ Mar 21 2009, 06:02) *
I see only two options here...

Might he not also be trying to prove a point to someone who relies too much upon spectral views to determine what "sounds" good? That would plausibly fit the concept of "noble cause," without necessarily making him a villain.

- M.
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[JAZ]
post Mar 21 2009, 20:06
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QUOTE (timcupery @ Mar 20 2009, 06:07) *
I assume you're talking about dithering. This basically adds noise to an audio stream, and as such fills in higher frequencies that may have been lowpassed out through encoding.



Were you serious?
First, i believe you wanted to say noise-shaping when you said dither, but even then, if that noise was of a comparable level of a content in those frequencies, it would be destroying more than helping. (Also, noise shaping increases with the frequency, and audio usually decreases with the frequency)


For the OP. You have another experiment, if you want: record the output of an (Creative) X-FI Soundcard with the "mp3 enhancer" enabled. The only problem is that it may change the audio too much.
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timcupery
post Mar 22 2009, 20:28
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QUOTE (eiko @ Mar 20 2009, 23:38) *
Yep. It's for a noble cause. ;)

It seems like none of us believe you that it's for a noble cause. Might you be willing to explain why it's something other than the three possible explanations that have been mentioned? If it is a different reason than one of those three?

QUOTE (ameyer17 @ Mar 21 2009, 11:48) *
EDIT: This moderation is getting to be a bit ridiculous. I'm leaving.

Get over it. A nice thing about HA is that people aren't full-quoting the post directly prior to theirs all the time, and this makes threads easier to read. Nobody hurt you.
Quoting is useful where you're replying to posts that aren't directly prior, or replying to a number of different things in a given post.

QUOTE ([JAZ] @ Mar 21 2009, 15:06) *

QUOTE (timcupery @ Mar 20 2009, 06:07) *
I assume you're talking about dithering. This basically adds noise to an audio stream, and as such fills in higher frequencies that may have been lowpassed out through encoding.

Were you serious?
First, i believe you wanted to say noise-shaping when you said dither, but even then, if that noise was of a comparable level of a content in those frequencies, it would be destroying more than helping. (Also, noise shaping increases with the frequency, and audio usually decreases with the frequency)

I was serious. Although I might have meant noise-shaped dither. I don't know all of the differences here. To my knowledge, dithering adds high-frequency noise and makes lowpassed audio streams appear (to a spectral analyzer) as if they weren't lowpassed.

This post has been edited by timcupery: Mar 22 2009, 20:29


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eiko
post Mar 23 2009, 23:56
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QUOTE (rpp3po @ Mar 21 2009, 04:02) *
QUOTE (eiko @ Mar 21 2009, 04:38) *
Yep. It's for a noble cause. wink.gif

Will check into these ideas thanks.


I see only two options here:

1.) He is a pirate of the lowest sort, who wants to share pseudo lossless files to be allowed to download other peoples' content.

2.) He's from an organization planning to demoralize the lossless sharing scene by injecting pseudo lossless files.
I sometimes contribute in a scene group myself so I have nothing against sharing lossless files in general and wouldn't release fakes under a scene release. But some people deserve it. smile.gif
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rpp3po
post Mar 24 2009, 02:39
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QUOTE (eiko @ Mar 23 2009, 23:56) *
I sometimes contribute in a scene group myself so I have nothing against sharing lossless files in general and wouldn't release fakes under a scene release. But some people deserve it. smile.gif


Moral arguments by so called 'scene' people are often the pinnacle of disingenuousness. Their whole trade is the hard work of others. They work against greedy corporations, who "don't sufficiently compensate artists anyway". Do 'scene' people compensate artists? Rivaling group B "deserves" fake lossless files, although they are doing exactly the same trade as group A.

Do what you want. Share your BS, but spare us the moral reasoning. It's built on sand.

This post has been edited by rpp3po: Mar 24 2009, 02:41
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greynol
post Mar 24 2009, 03:05
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I'm having a hard time finding a legitimate reason for this discussion to continue; especially since it's starting to go against the spirit of TOS #9.

This forum is not about helping people with illegal activities.


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