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Topic: Increasing / Decreasing MP3 Compression (Read 5542 times) previous topic - next topic

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  • FXtrader
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Increasing / Decreasing MP3 Compression
I need confirmation that I've got this right please......Look, If you rip an original CD track to MP3 @ 192 kbps, and then for whatever reason, decide to compress that MP3 even further - say to 128, that would result in an MP3 sounding pretty much similar to one that was ripped directly to 128....Am I Right ?

But, if you rip a CD track to MP3 @128, and then decide to increase that same MP3 to 192 kbps, you're not really going to get any improvement - or at least very little - as whilst the sound would be spread out further, there's no 'new data' to read as it's been discarded.....Am I Right ?

I Suspect this to be the simplest question ever asked but....well I need comfirmation !.....Thanks !

  • boojum
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Increasing / Decreasing MP3 Compression
Reply #1
1) Once it is compressed it cannot be made better.
2) Recompressing at a different rate will almost always degrade the resulting file.
3) So, always start from the original WAV file if you want a different rate MP3.

L8R

Nov schmoz kapop.

  • Jebus
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Increasing / Decreasing MP3 Compression
Reply #2
As boojum said, you're not quite right... every compression session throws stuff away. 128kbps will throw away more stuff of course, but then recompressing to 192kbps will throw away more stuff again so the second-gen 192kbps file will actually have LESS of the original audio data in it than the 1st generation 128kbps file.

Every time you compress at 128 you are essentially throwing out 91% of the original data (128/1440 kbps for uncompressed wave) Compressing at 192 throws out about 87% of the original data. Compressing at 128, then at 192 will result in even more data loss, of course.

Hope this makes sense. Don't transcode, essentially.

  • Defsac
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Increasing / Decreasing MP3 Compression
Reply #3
I tried some blind tests comparing transcoded and directly encoded MP3s using LAME 3.96.1. I found it did a fairly reasonable job at transcoding (though all the samples I tested were ABXable on the equipment in my signiture).

If you're not listening in critical listening conditions (if you're in a car or using a portable for example) you'll probably find transcoded MP3s encoded with LAME to be acceptable quality.
  • Last Edit: 26 August, 2005, 02:33:24 AM by Defsac

  • FXtrader
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Increasing / Decreasing MP3 Compression
Reply #4
OK, Thanks for replies....I get the 'jist'of it - I won't do that - I was more curious than seriously going to do that....Answers usually lead to more questions unfortunately....

As data is thrown out and permanently deleted from an MP3, why call it 'Compression'..... afterall, you can't 'Decompress' it then can you....a better term might be 'cannibalize'...!
Thanks...

Increasing / Decreasing MP3 Compression
Reply #5
easy, when you make something smaller it's called compression. It does not yet say anything about being lossy or lossless

  • Jens Rex
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Increasing / Decreasing MP3 Compression
Reply #6
Quote
As data is thrown out and permanently deleted from an MP3, why call it 'Compression'[a href="index.php?act=findpost&pid=322716"][{POST_SNAPBACK}][/a]

That's why we differentiate between lossy and lossless compression.

  • Sunhillow
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Increasing / Decreasing MP3 Compression
Reply #7
Quote
As data is thrown out and permanently deleted from an MP3, why call it 'Compression'..... afterall, you can't 'Decompress' it then can you....a better term might be 'cannibalize'...!
Thanks...
[a href="index.php?act=findpost&pid=322716"][{POST_SNAPBACK}][/a]


"Cannibalize" is good 

When MP2 and MP3 still were young, they were called "data reduction" which IMO is the right term for what it does