i have seen that once converted to mp3, the file cant be restored to its origional quality (though the mp3 is very good unless you have the ears of a clasical composer)
however, software like total audio converter that convert mp3 back to a wav file gives a wav file around the same size as an average wav, (about 10 x the size of the mp3.
if the data is lost in the shrinking process, where does the extra megs come from?
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An analogy would be changing a .jpg to .bmp
In both cases the original quality from the source is lost when converting to the lossy format (ie. the .mp3 or .jpg), but the uncompressed file is the same quality as the input lossy file (ie. the .mp3 or .jpg)
MP3 is not necessarily that good; e.g. if you use a low bitrate, you can tell the poor quality. AAC audio compression will give you better quality at the same bitrate (filesize).
Take a nice shiny, smooth piece of aluminum file. Wad it up into a little ball (compress it). Now open it back up (uncompress it). Notice how it's full of wrinkles.
Originally Posted by stewart2000
You can convert a track to mp3, back to wave, back to mp3, over and over. The filesizes will be the same. The quality will degrade a little each time you compress and expand it.
Same principle as jpeg compression of images. Convert jpeg to BMAP and back again a dozen times, see it getting fuzzier and blockier each time.
MP3 and JPEG compression is lossy. They look for patterns in the data and store the patterns. Small deviations from the patterns are dropped.
To put it in simple terms, WAV has a fixed bit rate (something like 1450 Kbps, but I don't remember the exact value - that is close though) so that's where the size comes from. WAV uses a bit rate significantly higher than MP3, so that's why converted files are quite a bit larger.
Take a list of 10 numbers. Compress it by removing 5 of the numbers. Uncompress it by adding 5 numbers. Your new list of 10 numbers probably won't contain the same 10 numbers as the original list but it's the same size.
That's essentially what's happening when you compress audio. You take a fixed size audio file (defined by the samples per second * bits per sample * number of channels * running time) and compress it by removing information. When the audio is decompressed it is restored to it's original size by restoring those original properties. But the decompressor can't restore all the values exactly as they were.
ok, thanks guys, i think iv got it now.
so once an audio file has been compressed to mp3 there is no point in uncompressing it again (unless it is for a cd player that doesnt play mp3's)
just a thought ... radio stations that store tracks on computer now, are they in mp3 or wav format, or even the cda format riped direct from cd?
think about FM radio stations which play music tracks 24 hours. they do keep hundred of thousands of music files.if it is stored in cda or wave format they need to have huge huge hard disks.
i think a few TB would do it,