Does amplification/de-amplification affect quality?

[xeen]

I'm wondering if changing the loudness of an audio music track affect its quality. For example, here is a picture of the original track (the loud one) and a picture of the same track when I de-amplified it to 80%.

http://erudition.illhostit.com/uploads/xeen_pic2.jpg

If you look at the original one, it looks like your normal wave (although a loud one). But after I made it less loud, it looks more like a rectangle than a wave. So my question is does the de-amplification process degrade quality by causing distortion? Or is it perfectly safe for me to lower the volume of my audio tracks before I encode them?


My second question is about the reverse process. Say I want to extract a piece of audio from a DVD and save it as an mp3. DVD audio tracks are usually not very loud for some reason (I mean the songs, not the speech). So after I extract it, but before I save as mp3, I like to amplify it some to make it the same loudness as my other mp3s. Does this cause any quality degradation? I understand that of course it does if I amplify it by too much, but does anything happen from an amplification of say, up to 200% ?

[jorel]

if the first picture had the same size of the second we could do some visual comparisons..maybe irrelevant but we don't have the source and the result of the music here to listen.

seems that you not only reduced to 80% but...
the second picture(result) seems normalized!
you don't normalize or something? :confused:


my opinion (humble):
don't normalize and if you feel that the souce is too loud,
only adjust the volume to ~90%-98%(depend the source).
don't forget that sometimes it can decrease the trebles and basses and the sound seems faded!
use sound forge, adobe audition or seamless.

when you normalize,you change the original dinamic of the source.
better adjust to you taste in equalizer/amplifier but using the source!
;)

[Imperial Llama]

Originally posted by xeen
If you look at the original one, it looks like your normal wave (although a loud one). But after I made it less loud, it looks more like a rectangle than a wave. So my question is does the de-amplification process degrade quality by causing distortion? Or is it perfectly safe for me to lower the volume of my audio tracks before I encode them?

The top wave is pretty rectangular too. The bottom wave is what I'd expect see if you reduced the top to 80%. A lot of popular music (I use the term in the broadest sense) is heavily processed to get it as loud as possible, and it's sadly all too common to see it looking (and sounding) distorted like that. De-amplification shouldn't cause any distortion like that.

Originally posted by xeen
My second question is about the reverse process. Say I want to extract a piece of audio from a DVD and save it as an mp3. DVD audio tracks are usually not very loud for some reason (I mean the songs, not the speech). So after I extract it, but before I save as mp3, I like to amplify it some to make it the same loudness as my other mp3s. Does this cause any quality degradation? I understand that of course it does if I amplify it by too much, but does anything happen from an amplification of say, up to 200% ?

Use besweet to convert AC3 to MP3 and tell it to normalize. Besweet's hybridgain option is a normalizing method and is recomend for AC3 to MP3 conversion by many people (including me) due to it's speed. Normalizing [to 100%] will make it as loud as possible without causing any distortion. I may have misunderstood jorel but he looks to be confusing normalization with dynamic range compression. Normalizing [to 100%] will not cause distortion.

Once you've finished encoding you can use something like MP3Gain to automatically adjust the volume of your entire MP3 collection so it all at approximately the same loudness.

[xeen]

ok in that case I think I need someone to explain to me in plain English what normalizing does. I'm using Adobe Audition/Cool Edit Pro (same thing). I just did a normalization to 80% and compared that to a de-amplification to 80%, and I don't see nor hear any difference. Is there a difference between the two and if so then which one to use when? I'm confused :(

[ursamtl]

As I understand it, all normalizing does is take the highest peak in an audio file and compare it to a target level. Then it takes the entire file and adjusts by the same amount. For example, if the highest peak in a file is at -3dB and you normalize to -1dB, then the entire file will be increased by by +2dB. In your case, de-amplification and normalization to the same level of 80% should have no difference.

True normalization is not supposed to change the dynamic range of the file. In other words, if the highest peak is at -3dB and you normalize to -1dB, if a given point in a file is at -10dB then it will be adjusted upwards to -8dB.

The flat tops of the peaks suggest that some kind of brick wall limiting or compression was used or else the file was overnormalized and clipped somehow. If normalization is not used properly or if the program is incorrectly written then it might cause this kind of problem, but normalizing to anything less than 0dB should not be a problem as it simply raises the loudest parts of your file to this level. I was reading an article in the latest issue of Sound On Sound magazine (excellent mag by the way) that suggested normalizing to -0.5dB just to allow a margin of error. Even -1dB should probably be fine. Notice that these are not percentages, but 100% on a decent program should be equivalent to 0dB.

Using something like MP3Gain should be ok as long as none of the files ever pass 0dB.

Having written all this, it's still a good idea to avoid using too much of this kind of thing. Some professional comments I've read on the subject consider normalization a complete no-no, whereas others use it regularly. As with all processing, a little goes a long way so don't overdo it.

Regards,
Steve.

[Soulhunter]

Originally posted by Imperial Llama

A lot of popular music (I use the term in the broadest sense) is heavily processed to get it as loud as possible, and it's sadly all too common to see it looking (and sounding) distorted like that. De-amplification shouldn't cause any distortion like that.

Noticed the same, I have way too much CD's with distortions... :angry:

So I got this this (http://mf.onthanet.nl/forum/thread.php?threadid=112&boardid=16&styleid=1&sid=13a5b308b4a3bc78763ae8606aa1d5c4) simple idea !!!


Bye

[ursamtl]

Originally posted by Soulhunter
Noticed the same, I have way too much CD's with distortions... :angry:

So I got this this (http://mf.onthanet.nl/forum/thread.php?threadid=112&boardid=16&styleid=1&sid=13a5b308b4a3bc78763ae8606aa1d5c4) simple idea !!!


Bye

Your idea looks extremely cool. How does it sound? Any test results? I've been extremely peeved about the idiots who compress the heck out of popular music lately as well. Some new releases are massacred by this!

[Soulhunter]

Originally posted by ursamtl

How does it sound? Any test results?

Ehm, its only a idea...

I made the last pic with Photoshop to visualize my idea !!!

Im not a programmer, someone else should code this... :o


Bye

[ursamtl]

Originally posted by Soulhunter
Ehm, its only a idea...

I made the last pic with Photoshop to visualize my idea !!!

Im not a programmer, someone else should code this... :o


Bye

Ok, fully awake now on this end.:o I believe there are some wave reconstruction tools in Wavelab and Audition, but I've never tried them. The problem I'm seeing is that entire CDs are being so overcompressed that restoring the peaks would take forever! And then the music industry wonders why people don't want to pay $20 for a CD!

[Soulhunter]

Originally posted by ursamtl

And then the music industry wonders why people don't want to pay $20 for a CD!
Originally posted by Soulhunter (some time ago...)

Anyway...

Most of the money Ive spend for CD's in the past, I spend now for DVD's and PC games !!!

Reason for this ???

* 5 different (M)TV channels and countless radio stations playing the top 100 24/7 in-loop...


Also the quality of mainstream music has decreased (IMO very much...) the last years !!!

* 2 out of 10 CD's with distortions, 4 out of 10 with clicks, 6 out of 10 compressed to hell...

[Slogra]

Originally posted by xeen

My second question is about the reverse process. Say I want to extract a piece of audio from a DVD and save it as an mp3. DVD audio tracks are usually not very loud for some reason (I mean the songs, not the speech). So after I extract it, but before I save as mp3, I like to amplify it some to make it the same loudness as my other mp3s. Does this cause any quality degradation? I understand that of course it does if I amplify it by too much, but does anything happen from an amplification of say, up to 200% ?

The problem is not that your DVD are too soft, but the problem is that the mp3s/cd audio are WAY too loud.

They make the sound of CDs as loud as possible by using a compressor. A compressor is like an automatic volume button that goes up when the sound drops below a certain volume. They do it at such an extend that all natural peaks of the sound are gone. You can make a CD quite loud with this method without letting it clip, but it'll sound quite different than the original recording (not just louder).
After they made everything equality loud (remove all natural dynamics), they often decide to make it even louder and the song starts to clip at many, many places.

I'm sure all cd masterers know what they are doing and know that they f*ck up the sound.
But i guess their bosses (who just want to see money) don't know anything about audio engineering, and just want the cd to be as loud as possible. They probably don't even compare the original version and the squashed and clipped afterwards at the same volume.

BAM! Another CD went to hell. :scared: