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is WAV normalization lossless?, such as MP3 with MP3Gain
Farpenoodle
post Mar 21 2006, 03:37
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There should be no reason for language ninjutsu here.

It should be very clear if a process is lossless or not. It should not even factor if changes due to processing are subjectively noticeable or not. If data is lost or changed in the process, it is lossy. I'd like to think that yes, our definition is 'technically correct.' Considering I have no idea you can manage to extrapolate any other definition from the word, 'lossless.'

Being subjectively lossless doesn't make it lossless.


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AndyH-ha
post Mar 21 2006, 04:41
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It has nothing to do with subjective. It is the standard use of the word in the world outside HA. That does not include "data is ... changed in the process." This isn't hard to understand.

Maybe I'm wrong. I've asked for a source other than people's emotions quite a few times now. I can find plenty of sources for my belief. It is possible none of them say anything like 'exclude other possible descriptions,' but there don't seem to be any standard accepted definitions that fit the local usage, while what I've said about it is found all over the place.
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kl33per
post Mar 21 2006, 04:50
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Actually, i'll think you find that outside the world of HA, if data is changed in the process, it's still called lossy, otherwise WinZip/WinRAR/7-Zip would not work.


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Farpenoodle
post Mar 21 2006, 04:59
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Well if people outside of here are referring to a lossy process as lossless (or the other way round) then all it means is that they lack understanding of how digital compression works. The definition of lossless should be implied by the word itself.

Just because alot of people are using the term wrong does not mean the definition should change.


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bryant
post Mar 21 2006, 06:22
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I'm not interested in getting into the "what is lossy" debate, but I would like to add something about wav normalization.

Using the strict mathematical sense of the word lossless, a wav normalization in the increasing direction (i.e. gain > 1.0x) would theoretically be lossless because it could be exactly reversed, even if pseudorandom dither had been applied (true random dither would destroy information, but I don't suspect that's too common). Of course, a little information would have to be stored about how the transformation was done (like MP3Gain).

On the other hand, wav normalization that reduces the level is certainly lossy, effectively raising the noise floor by the same amount as the audio is reduced. And this is, unfortunately, the direction that ReplayGain generally turns out to be.

edit: added paragraph break

This post has been edited by bryant: Mar 21 2006, 06:24
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suhrim
post Mar 21 2006, 07:14
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QUOTE (jaktek @ Mar 20 2006, 04:40 AM)
If you look at what Burrrn is actually doing, you will find that steps 1 and 2 are completely unnecessary.  Burrrn does not use the Foobar replaygain values;  it takes the wav files (after decoding if necessary) and applies WaveGain to them.
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You can edit the parameters for the decoders so that it uses replaygain when decoding. In Settings look at the Decoders tab.

This post has been edited by suhrim: Mar 21 2006, 07:17
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jaktek
post Mar 21 2006, 07:56
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QUOTE (suhrim @ Mar 20 2006, 10:14 PM)
QUOTE (jaktek @ Mar 20 2006, 04:40 AM)
If you look at what Burrrn is actually doing, you will find that steps 1 and 2 are completely unnecessary.  Burrrn does not use the Foobar replaygain values;  it takes the wav files (after decoding if necessary) and applies WaveGain to them.
*


You can edit the parameters for the decoders so that it uses replaygain when decoding. In Settings look at the Decoders tab.
*



How exactly would you do this? I.e. what are the correct parameters? I'd like to have this information, could come in handy.

This post has been edited by jaktek: Mar 21 2006, 07:56
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AndyH-ha
post Mar 21 2006, 08:55
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QUOTE
Well if people outside of here are referring to a lossy process as lossless (or the other way round) then all it means is that they lack understanding of how digital compression works. The definition of lossless should be implied by the word itself.
Just because a lot of people are using the term wrong does not mean the definition should change.
You have not read this discussion. Its content is not what you addressed.

QUOTE
  Actually, i'll think you find that outside the world of HA, if data is changed in the process, it's still called lossy, otherwise WinZip/WinRAR/7-Zip would not work.
These examples are all compression schemes. This IS where lossy/lossless are used correctly, unlike in most posts of this debate.

QUOTE
Using the strict mathematical sense of the word lossless, a wav normalization in the increasing direction (i.e. gain > 1.0x) would theoretically be lossless because it could be exactly reversed, even if pseudorandom dither had been applied (true random dither would destroy information, but I don't suspect that's too common). Of course, a little information would have to be stored about how the transformation was done (like MP3Gain).
On the other hand, wav normalization that reduces the level is certainly lossy, effectively raising the noise floor by the same amount as the audio is reduced. And this is, unfortunately, the direction that ReplayGain generally turns out to be.
None of this debate is about whether or not information is changed or whether or not it is a reversible change. It is all a rather funny bit about the adjectives applied to the processes. Some processes are destructive and irreversible, but find the dictionary or textbook that calls them 'lossy' simply because of that. A lossy process is one where data is deliberately discarded, according to some systematic rules, not one where there are simply rounding errors.
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hawkeye_p
post Mar 21 2006, 09:05
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So rounding is not discarding data (digits) according to systematic rules ?
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stephanV
post Mar 21 2006, 09:06
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AndyH: since you have sources that back up your claims, why don't you just post them. This debate is getting rather silly proportions.


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AndyH-ha
post Mar 21 2006, 11:21
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Put "lossy" into Google and get pages of references. Look at what they are about. These include a variety of dictionary and encyclopedia entries, and a large number of articles about ----- data compression. Yes, it is a bit silly, but it has been amusing.

No, I would say that when you have a number container of a specific precision and it is obviously the case that it is impossible for it to hold any greater precision, doing calculations with it is not discarding data. It might or might not involve reducing precision of some of the results. Do you understand "significant figures?" Quite aside from the terminology, it can't be discarding data if it isn't data.
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Big_Berny
post Mar 21 2006, 11:56
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Surely a comression is lossy if the original data can't be restored bit-by-bit!

But for me the question is: Will the round not appear if you use replaygain? Isn't the audio-output (on the soundcard) of a levelled wav not the same like the original wav with replaygain?

That would mean that it isn't "more" lossy than replaygain....

Big_Berny

This post has been edited by Big_Berny: Mar 21 2006, 11:57
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stephanV
post Mar 21 2006, 12:16
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AndyH-ha: Do a search for lossless-join decomposition (funny enough also related to 'normalization' smile.gif ). A decomposition is called lossy when the original data cannot be uniquely recovered (iow the process is not reversible). So now you have the word lossy used in a "technical" context where indeed whether the process is reversible or not matters.

Big_Berny: the difference is the reversibility of ReplayGain (can be done) and normalization (cannot always be done).


edit: spelling, spelling, spelling...

This post has been edited by stephanV: Mar 21 2006, 12:21


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Big_Berny
post Mar 21 2006, 12:56
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Yes, I know. But there isn't a difference in the soundquality, right?
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uart
post Mar 21 2006, 14:59
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Garf essentually said in the first two replys of this thread that

1. Wave normalization is not generally lossless.

but

2. For the proposed usage the extent of data loss would be neglegable.


I don't believe we have moved from this point. It was correct then and is correct now.

The only other worthwhile thing that has been brough forth is Bryant's observation that upward wave gain is generally reversable (not withstanding clipping or non-deterministic dither).
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Otto42
post Mar 21 2006, 16:34
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QUOTE (AndyH-ha @ Mar 21 2006, 04:21 AM)
No, I would say that when you have a number container of a specific precision and it is obviously the case that it is impossible for it to hold any greater precision, doing calculations with it is not discarding data. It might or might not involve reducing precision of some of the results. Do you understand "significant figures?" Quite aside from the terminology, it can't be discarding data if it isn't data.
*

Reducing precision is indeed discarding data, when the precision can never be recovered.

The stumbling block here seems that you only apply the terms "lossy" and "lossless" with regards to compression. However, the rest of the world applies them more generally to processes of any sort. A process is lossless when it can be reversed. Nothing is lost.

Compression is a process. But then, so is rounding (or truncating, as the case may be). Applying the terms lossy and lossless to both of them is equally justified.

Furthermore, you went on earlier about the "amount" of change being a factor, but the terms are not that specific. Yes, the amount of loss in a rounding operation like this being applied to a WAV is extremely small, but it nevertheless exists and is real. It is indeed lossy. If you want to apply a judgement call on the amount of change, then where, exactly, do you draw the line in the sand between lossy and lossless? A normal person would say "if there is loss, then it is lossy", because that would be the obvious line.

Well, there is loss. You can never recover that precision. It is, in theory, audible. It is a loss that is additive over multiple operations (this being why most good audio programs actually represent the data as floating point in memory, only converting to 16-bit when saving). Okay, so it's minor, but that does not matter when the question is "is it lossy?".


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SMT [AQP]
post Mar 21 2006, 17:02
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WTF is this so difficult to understand ?
If the change is irreversible, it is lossy. End of story.
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AndyH-ha
post Mar 22 2006, 03:32
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QUOTE
Surely a comression is lossy if the original data can't be restored bit-by-bit!
But for me the question is: Will the round not appear if you use replaygain? Isn't the audio-output (on the soundcard) of a levelled wav not the same like the original wav with replaygain?
That would mean that it isn't "more" lossy than replaygain....
The part about lossy comression is true, but unfortunately you don't win any points because you have not figured out what this debate is about (hint: it is not that).

I'm not sure what you are asking in the second part of your post, but as to what I think you are asking, the answer is ‘there is no difference between normalization and ReplayGain' so far as what comes out the end of the reproduction chain for you to hear. They are both doing the same thing to the data, giving the same result. The difference is that ReplayGain does it in real time each time the audio is played, normalization does it one time by modifying the source data.

QUOTE
Do a search for lossless-join decomposition (funny enough also related to 'normalization'
I'm not sure if this is offered tongue-in-cheek or not. It does point out a legitimate technical use of the words unrelated to data compression, so I have to concede that, but alas, this use is quite unrelated to audio or signal processing. Also, I don't think you can, by any stretch, draw an analogy between database normalization, or measurement normalization, and audio file normalization.

QUOTE
The only other worthwhile thing that has been brough forth is Bryant's observation that upward wave gain is generally reversable (not withstanding clipping or non-deterministic dither).
Using "wave gain" where the discussion was about normalization is getting kinda sloppy in the current context. Regardless, I think what bryant said in that post is not true, at least as stated. Am I missing something?

Usually we are discussing 16 bit integer data, simply because that is most what people here deal with, but this should apply in the same way to 32 bit or 64 bit floating point (or whatever format):
Initially, each sample is some specific value. Once the file is normalized, each sample is some new value. This new value is arrived at by applying a factor to the original value via a multiply. If the transform is dithered, additional changes are applied.

There now exist some particular difference between the original sample value and the new sample value -- but, at least for the normalization part, it is a different difference for each sample. Therefore, to be able to get back exactly to the original, that specific difference must be stored for each sample. It can not be recalculated from a single factor the way the normalized value was calculated. That is the reason it is irreversible.

This is not a ‘little' information that has to be stored, relative to the amount of original data. (Some, probably quite small, amount of lossless data compression might be done on this difference data to take advantage of the places where some number of adjacent samples have exactly the same value, or possibly where there are more complex patterns.)

The storing of difference data and the restore of the original values would work exactly the same way whether the normalization increases or decreases the amplitude, or even if it results in clipping. The noise floor does not enter into consideration.

QUOTE
Reducing precision is indeed discarding data, when the precision can never be recovered.
The stumbling block here seems that you only apply the terms "lossy" and "lossless" with regards to compression. However, the rest of the world applies them more generally to processes of any sort.
Let's consider a reasonable example that isn't lossy data compression, such as resampling 16 bit to 8 bit. There are probably audio operations other than resampling that might be used, but none come to mind at the moment. In most transforms, such as normalization, to choose another example, there is no loss of precision.

Resampling to a lower bit depth (or sample rate) indeed results in a loss of data, and it is deliberate. Its magnitude is probably comparable to that of fairly severe (i.e. to low bitrate) lossy compression, but I don't see its parameters as comparable to the ‘deliberation' that is done in lossy compression, a choosing of what data to discard in order to achieve a particular goal. I guess that could be argued either way.

More important for this debate, however, is that ‘lossy' just isn't the term applied to it. You say "the rest of the world applies them more generally to processes of any sort." That is exactly what is not true.

QUOTE
WTF is this so difficult to understand ?
If the change is irreversible, it is lossy. End of story.
And you know this because you had a mystic insight into the true nature of life, the universe, and everything? Because your mother told you so? Because you have an emotional need for it to be so?

You also are missing the point of this debate. Your heart-felt declaration of your belief does not make it factual. You need evidence to back up your claim. It is not self evident and it is not available from an examination of the process. ... I don't believe evidence exists (that supports your position).

This post has been edited by AndyH-ha: Mar 22 2006, 03:35
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Farpenoodle
post Mar 22 2006, 04:25
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So what do you want to call it then?

A 'sorta-lossy' process?

That's still lossy.


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Destroid
post Mar 22 2006, 07:42
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Yuck.

In the professional meaning of the word, permanently adjusting volume levels of audio data will never be considered "lossless."

But whatever, not everyone is a professional biggrin.gif


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AndyH-ha
post Mar 22 2006, 07:48
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This isn't about what I want to call a destructive edit, it about what the 'professional' audio world calls it. Being professional 'they' are a little more exacting with their use of technical terms than is this neighborhood.
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kjoonlee
post Mar 22 2006, 07:57
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The first person who replied on this thread is a professional, you know.


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Farpenoodle
post Mar 22 2006, 08:00
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They call it 'adjusting the volume?'


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cliveb
post Mar 22 2006, 10:43
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This thread has developed into a rather deep philosophical debate, which is all very well, but unfortunately the OP's original question seems to have been largely forgotten, and (s)he is probably still wondering what (s)he needs to do to achieve his/her goal. To recap:

QUOTE (Bourne @ Mar 19 2006, 09:10 PM)
My goal is to burn a standard Audio-CD with CDDA(WAV) tracks with mixed music/artists, but each music has its own volume level. Burning the lossless WAV of course does not alter the data, but the volume levels for each track are all different. Is there any special process one could do in order to level the tracks equally?
*


Let's begin by noting that *normalization* of WAV files will not achieve Bourne's goal. The generally accepted meaning of "normalization" is the application of linear gain so as to bring the peak level of the file to a standard level (typically 0dB). However, the perceived loudness of a track is just as much dependent on the dynamic range as it is on peak levels. Therefore simple normalization won't do what Bourne wants.

Algorithms such as ReplayGain will determine the linear gain required in order to achieve a given perceived loudness by taking into account the dynamic range as well as the peak level. However, if the original file has a very large dynamic range, there is a danger that the required gain is so great that it would result in the peak levels being pushed into clipping. And you *really* don't want that to happen. In order to avoid this, you have three options:
(i) choose a very low "target loudness" for the ReplayGain algorithm, so that all linear gains calculated are certain to be less than unity (ie. result in a loudness *reduction*). The downside to this is that all your mix CDs will be very quiet.
(ii) Accept that those files with a large dynamic range are going to sound a bit quieter, and apply the maximum possible gain without causing clipping - in other words, normalize those files to 0dB. The downside here is that your mix CDs will still have variations in loudness between tracks.
(iii) Apply some dynamic range compression so as to reduce the dynamic range of the quieter files, which makes them sound louder. The downside here is that dynamic range compression tends to "squeeze the life" out of music, so it should only be used in moderation.

I don't have any practical experience using WavGain, but my understanding is that it uses the ReplayGain algorithm to determine a linear gain that is applied to the WAV file. I don't know whether it backs off the required gain in order to avoid introducing clipping - perhaps someone else here can verify this.

If you want to persue option (iii), then you might like to try out a piece of shareware I wrote called Volume Balancer. It doesn't use the ReplayGain algorithm as such, but it does use similar dynamic range measurement to determine perceived loudness and then applies linear gain and/or dynamic range compression in order to bring a set of WAV files to a defined level. It only uses compression where the target loudness cannot be achieved through linear gain adjustments.

One last thing. *All* of these processing options for WAV files result in non-reversible changes to the audio data, and so in a formal sense they are "lossy". But from a practical point of view options (i) and (ii), which involve only linear gain adjustments, are benign. Option (iii) is less benign, but may in some circumstances be the best compromise.
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AndyH-ha
post Mar 22 2006, 11:22
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Bourne, the original inquirer, asked about CoolEdit's Group Waveform Normalize which I believe is an RMS based process used to balance perceived loudness. I'm not positive about that, as I've never had interest in doing that task, but I seem to recall reading that is its purpose.

You introduce a new descriptor "formal sense" into the debate. Have you any evidence, that being the sticking pont or the whole issue? I maintain that is an incorrect use of the term lossy. Its not losing anything, its changing it, but more importantly, it isn't the accepted technical use of the term.

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