No, I don't think so. Was: [vorbis] Vorbis 1.0 binary - Beta4 still the best?

[Luke Usherwood]

Yes, the ratio of an uncompressed file to a compressed file can be used as a crude estimate of the "entropy" or information in a file.  But lossy compression does not necessarily reduce the entropy.  Lossy compression may result in a proportion of the original information changing to something different, but equally complex as so far as the Flac encoder is concerned.

For an example that may be easier to visualise... Imagine you have an picture with a sharp transition, like a black rectangle on a white background.  You then compress that file to a JPEG.  When you view (decompress) the image, it has little artefacts (waves) on either side of the transitions. The resultant image now has MORE information (complexity) than before compression.  If you now compress this file in a lossless compression scheme, such as PNG or GIP, it will actually be much (much!) bigger.

<p><p>At 09:58 13/07/2002 -0500, you wrote:

<p>>Steve Bergman wrote:
>
>>
>>Call me an audio compression newbie, but I have a question.  The unflac'd versions of all three files are exactly the same size. (md5sums differ, however.)  If information has been lost in two of the files through vorbis encoding and flac is lossless, shouldn't they be smaller than the original?
>Oops.  I see my fallacy.  wav is constant bit rate and silence takes just as many bits as anything else.  However, let me try again.  The file sizes of the compressed flac's are also very similar.  Isn't the ratio of file sizes of the losslessly compressed data and indicator of the percentage of information lost?  I would have expected the losslessly compressed/decompressed ogg samples to be much smaller.  Does the ogg decoder try to fill in lost information through interpolation or something which then has to be losslessly encoded by flac, taking up about the same amount of space?
>
>-Steve

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