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[benn600]

It seems like the estimates for VBR encoding are falling short.  I once burnt a CD with tons of FLAC to be converted to MP3.  MC immediately removed a whole pile of the songs and when it was finished burning the CD, it had burnt under 500 MB.  Now my question is if there would be a way to calculate a more accurate estimate based on the FLAC bit rate.  Is there any correlation between a VBR MP3's size and the relative size of a FLAC file?

For example, take 3 songs.  In FLAC, 1=10 MB, 2=20MB, 3=30MB.  If all these songs are the same length (duration), then the bit rate should be much greater on 2 and 3.  So, wouldn't the MP3 size be larger for the second and third?  Considering there is probably some similarities, could this concept help get better estimates?

[scthom]

You'd have to do some statistical analysis to determine if a correlation exists.  I expect there would be rough correlation but not enough to get that close.  The problem is that the flac file can tell you what size/duration the raw file would be, but until you do the analysis, MP3/VBR can't tell you what size it will be afterwards.

Since both formats are VBR, there ought to be some minor correlation between them, but because you are throwing some parts away with MP3, it probably throws off the statistics.  You could probably say that if it's a big flac, it's probably a big MP3, but that's about it.  Not enough to make an estimate of file size.

[benn600]

Is the estimate purely based on duration and average sizes?

[scthom]

Is the estimate purely based on duration and average sizes?

No idea what they use.  I expect it would be duration, with a factor for how small you can make it given VBR on a "typical" file.  As you know, that factor varies widely within each track but also style to style.