Is it true that MP3's loose their quality over time?

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#611621 19-Apr-2012 06:31

This seems to have been posted around Oct'09. Very interesting read... http://www.head-fi.org/t/451369/why-flac-is-better

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#611624 19-Apr-2012 07:08

*face palm

Handle9

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#611627 19-Apr-2012 07:26

You should tell him that he is correct and that the same algorithm is used for banking software so your balance is automatically reduced by 12% every year.

cyril7

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#611631 19-Apr-2012 07:57

Have any of you ever written signal processing code that includes voice coding, I have and its deployed in a number of telco based products used around the world, mainly military.

Coding for MP3 is partially asymetric, MP2 video is heavily assymetric, ie the coder does most of the work the decoder is less complex therefore some of the rules a coder may have done or not done in the early days may not apply in these mip rich days.

This is more apparent with MP2 video coding, ever wondered how over time sky keep putting more channels in to a spectrum but the pictures dont get dramatically worse and your decoder was never changed.

Even with audio it was common if you had meager resources to apply more pre filtering than might be desirable, there are probably 3 or 4 stages or sub routines where you can do more or less work but still get working outputs.

So yes a coder today probably provides a better quality for a certain bitrate than older coders but we are probably talking about some pretty old examples here.

As for any implication of the coder result spoiling with time, well that rubbish unless the file becomes corrupt.

Cyril

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#611633 19-Apr-2012 08:03

I think this must be fundamentally incorrect. Here is my proof....

I have noticed in older (digital) photos I appear slimmer than in more recent photos.

Therefore I would say that the photos must be distorting over time and as they digitally age, the size of the subject is getting larger.

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grant_k

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#611638 19-Apr-2012 08:18

cyril7: This is more apparent with MP2 video coding, ever wondered how over time sky keep putting more channels in to a spectrum but the pictures dont get dramatically worse and your decoder was never changed.

A TV industry insider tells me that they use a gadget called a "Stat Mux" to cram more channels in. IIRC, this means Statistical Multiplexer, and relies on not all channels requiring the full bandwidth of a mux or satellite transponder at any given time.

However, in Sky's case, the compression on some channels like BBC World is so great, the picture increasingly looks like crap. Recently I downloaded BBC Click via iPlayer and was amazed at how much better it looked.

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#611655 19-Apr-2012 09:05

Here is an article I found (wrote) just now that explains why MP3's degrade over time.

Its all to do with Osmosis, the 1's and 0's (ones and zeros) sit right next to each other in a file and over time due to digital osmosis small amounts of the 1 are absorbed by the 0 which lessens the value of the 1 slightly and increases the value of the 0. So after say 10 years the 1 can drop down to .9 while the 0 will rise to around .1 . Its 100% exactly the same as positive and negative charges attracting each other, but totally different and unrelated in any way.

So when playing an MP3 say 10 Years After (or any band for that matter) the 1's wont quite hit 1 anymore and the 0's will almost get down but wont quite boogie. This results in the quality sounding a little Muddy and Watery and lacking Clarity.

This doesn't happen with FLAC files though because although they are exactly the same as MP3 as far as using 1's and 0's they are completely different due to the buffer between the 1 and 0, a jacket if you will, that stops the Osmosis effect and also protects the file from being damaged by small arms fire.

The reason I know all this is that I have found a way to protect and even restore MP3 with a special piece of wire that when put next to any digital file will restore it back to its former glory. Tell your mate to keep an eye on Trade Me if he wants one.

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#611658 19-Apr-2012 09:19

I do have MP3's that have developed clicks in them...
Also JPG's that have funny colours thru them.

Im pretty sure however that this was all the result of me copying them off a HDD that had bad sectors and was dying... :)

Doing your best is much more important than being the best.

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#611668 19-Apr-2012 09:38

A TV industry insider tells me that they use a gadget called a "Stat Mux" to cram more channels in. IIRC, this means Statistical Multiplexer, and relies on not all channels requiring the full bandwidth of a mux or satellite transponder at any given time.

However, in Sky's case, the compression on some channels like BBC World is so great, the picture increasingly looks like crap. Recently I downloaded BBC Click via iPlayer and was amazed at how much better it looked.

Morning Grant, yes I guess the last increase of capacity has come about by deploying stat muxs, a logical move. However the current Tandberg coders they use provided a 2.5-3x decrease in bitrate compared to the units they replaced, if anything when first deployed (and that drop in bitrate was felt) about 7-8yrs ago the images in anything improved over their old coders. Since then I think Tandberg have provided 2 or 3 software upgrades to reduce bitrates even futher, but as to if SkyNZ has taken/paid for those upgrades I have no idea. What is important, at no time did you decoder change. But agreed some of the current pics are awful, the FreeView TV1/2 off Sat which are also seen by Sky SD customers are shockers.

MP4 AVC is even more asymmetric, currently there are a number of clever coding techiniques that are not deployed due to the fact they need even more mips than economic and or only work with non realtime multipass, often these are used for BlueRay authoring but not feasible in live broadcast arena's.

Cheers
Cyril

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#611669 19-Apr-2012 09:39

xpd youve screwed the page

Cyril

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#611670 19-Apr-2012 09:42

Whoops...attempting to fix :D

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#611671 19-Apr-2012 09:42

Maybe the person who wrote the original article didn't realise that his hearing was degrading over time and attributed the SQ loss to bit loss :-)

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#611672 19-Apr-2012 09:43

Hid my post... Ill repost in a happier state later ;) (Rather than break GZ)

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#612043 19-Apr-2012 17:52

If the MP3s are stored on a CD they'll eventually degrade due to the organic materials the data is stored on decaying. On a hard-drive the magnetically stored data will _eventually_ lose its charge, but that could take decades on modern drives.

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#612109 19-Apr-2012 20:04

LOL. I read that as "is it true that MPs lose their quality over time" and I wholeheartedly agreed.

when I realised we were actually talking about a digital music format, I then had to disagree.

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