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Re: higher compression ratios in FLAC

Reply #25
My music was encoded long ago with unknown settings, likely the default of whatever software package  was used, so it is my guess that they were not particularly aggressive.
OK. Settings may have been -8 originally though.

It is most often possible to find out what FLAC version is used to encode, but not the setting. If you are on Windows, I suggest foobar2000 - not only is it a good player, but it is also one where you get a lot of support here. It can display tool used (see attachment), and it can convert everything too.

I understand that if music encodes with -8 at some ratio, then that ratio would be very close to the best possible encoding.  Such is how the -8 option is documented. 
Yeah, pretty much.
There are limits to what whatever codec can achieve. FLAC did not target the absolute maximum compression level, but rather decoding speed (= battery life!). Imprecisely speaking, a heavier option will search further for patterns to compress, and that takes time; there is a heavier setting than "-8" that can do a "more brute force" search for a fewer-bytes representation, but that is slow. For practical purposes, a you would rather have it perform a "clever search" over functions that are tested to perform well.

-8 was revised some time ago, because there were found functions that seem to do a better job on the average. That does not rule out that new -8 does slightly worse than old -8.

Furthermore, if you compare file size after re-encodings, there is something called "padding". By default, the reference encoding pads up the metadata block with an empty 8 kB to make room for re-tagging; when that is spent, it will have to re-write the entire file, and that takes much more time than just overwriting a small part of a file. You can switch off in the encoding process, but I wouldn't.

My situation now is one of is trying to determine what amount of saving I can get by re-encoding, and how best to do it.

Here is what I would do, assuming that you have hard drive space to spare:
- Use foobar2000 or the audiotester.exe utility to check integrity of your lossless files. (If they are corrupt, you do not want to re-encode; re-encoding will leave the false impression that everything was right.)
- Use foobar2000 to convert with -8 with a naming structure that completely mirrors the one you had. (Any corrupt ones: copy rather than re-encode.)
- Use foobar2000 with foo_bitcompare to compare - bit by bit - old against new. Then you have safeguarded against any wrong overwrites.
Now you have a backup. If you absolutely want to keep the file-by-file smaller one, then use a copy utility that skips overwriting based on size.

(There is a "FLAC frontend", but it has eaten files of mine. Avoid.)

one of the potential targets is my mobile device.
If you cannot fit it all: Go lossy. mp3 or something.
Memento: this is Hydrogenaudio. Do not assume good faith.


Re: higher compression ratios in FLAC

Reply #26
Once in a while this topic arises and the last time i checked CUEtools flake -8 compressed slightly better here compared to flac -8 -ep on a mixed genre test corpus while being much faster.
It creates standard spec files but uses bigger blocksizes for high samplerate material.
You may use it with -b 4096 then for a blocksize of 4096 for everything like reference flac does.
Is troll-adiposity coming from feederism?
With 24bit music you can listen to silence much louder!

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