[Flac] FLAC suddenly compresses more - why?

[Rene Boers]

Hi guys,
I use EAC to save and compress my CD's to my network drive. In the past my
compression to Flac was slightly worse than the file size shown by EAC. Now,
since about two weeks ago, my compression ends up at about half the size of EAC
i.e. I went from a compression ratio of approx 70% to a ratio of 30%. I get the
feeling that the compression is somehow missing something. Or is the intial
conversion to *.wav files not working properly?
Any help I can get on testing the process etc would be appreciated.
Note: I removed EAC and reinstalled to the latest version, but the compression
was still the "fantastic"30%.

Regards,
Rene




-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.xiph.org/pipermail/flac/attachments/20101226/a8847418/attachment.htm

[yahoo2]

Post by Rene Boers
Hi guys,
I use EAC to save and compress my CD's to my network drive. In the
past my compression to Flac was slightly worse than the file size
shown by EAC. Now, since about two weeks ago, my compression ends up
at about half the size of EAC i.e. I went from a compression ratio
of approx 70% to a ratio of 30%. I get the feeling that the
compression is somehow missing something. Or is the intial
conversion to *.wav files not working properly?
Any help I can get on testing the process etc would be appreciated.
Note: I removed EAC and reinstalled to the latest version, but the
compression was still the "fantastic"30%.
Regards,
Rene
_______________________________________________
Flac mailing list
Flac at xiph.org
http://lists.xiph.org/mailman/listinfo/flac

Sounds like your getting the default compression instead of a
compression of level 8,

[Fernando Alberto Marengo Rodriguez]

Hello Rene,
If you want to be sure that you get no information loss, I suggest a very simple test. Recover your WAV file from any of the FLAC files you mentioned in your e-mail. If this WAV file is bit-by-bit identical to the input WAV file, then you have no information loss.
Also, it is important to take into account that the compression ratio is highly dependent on the encoded wav file. If you are processing CDs, the compression ratio?for rock and pop music?is tipically 45 % to 70 %. For other kinds of music such as jazz, the compression ratio may be from 25 % to 40 %.
What kind of music have encoded so far?
Regards,
Fernando A. Marengo Rodriguez, PhD

Acoustics and Electroacoustics Laboratory

School of Electronic Engineering

Faculty of Sciences, Engineering and Surveying

National University of Rosario

Rosario, Argentina



-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.xiph.org/pipermail/flac/attachments/20101227/a21fb9bf/attachment.htm

[Brian Willoughby]

Post by Fernando Alberto Marengo Rodriguez
If you want to be sure that you get no information loss, I suggest
a very simple test. Recover your WAV file from any of the FLAC
files you mentioned in your e-mail. If this WAV file is bit-by-bit
identical to the input WAV file, then you have no information loss.

This is a good test, but keep in mind that only the audio part of the
WAV file will be identical. There are non-audio parts to a WAV file,
and those may be lost or changed when compressed, so you will need
some method of comparing only the audio and not the rest of the
file. In other words, a basic file to file compare might fail even
if the audio is the same.

I'm not sure how to compare the audio part only, at least not
easily. You can place each file in the same DAW, but with one set
for inverted polarity. Then mix them together and you should get
silence. But that is not an easy or simple test.

Brian Willoughby
Sound Consulting

[Gregory Maxwell]

Post by Brian Willoughby
This is a good test, but keep in mind that only the audio part of the
WAV file will be identical. ?There are non-audio parts to a WAV file,
and those may be lost or changed when compressed, so you will need
some method of comparing only the audio and not the rest of the
file. ?In other words, a basic file to file compare might fail even
if the audio is the same.
I'm not sure how to compare the audio part only, at least not
easily. ?You can place each file in the same DAW, but with one set
for inverted polarity. ?Then mix them together and you should get
silence. ?But that is not an easy or simple test.

Use raw files. E.g. the --force-raw-format with the flac command line command.

[rappard]

Post by Brian Willoughby

Post by Fernando Alberto Marengo Rodriguez
If you want to be sure that you get no information loss, I suggest
a very simple test. Recover your WAV file from any of the FLAC
files you mentioned in your e-mail. If this WAV file is bit-by-bit
identical to the input WAV file, then you have no information loss.

This is a good test, but keep in mind that only the audio part of the
WAV file will be identical. ?There are non-audio parts to a WAV file,
and those may be lost or changed when compressed, so you will need
some method of comparing only the audio and not the rest of the
file. ?In other words, a basic file to file compare might fail even
if the audio is the same.
I'm not sure how to compare the audio part only, at least not
easily. ?You can place each file in the same DAW, but with one set
for inverted polarity. ?Then mix them together and you should get
silence. ?But that is not an easy or simple test.

Caveat: I've never tried any of these, but these have come up in
various HA threads I've read over the years:

Audacity
EAC: Compare WAVs (CTRL-W)
foobar2000: bit-compare two tracks
(http://www.foobar2000.org/components/view/foo_bitcompare)

Cheers,

Martin