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  1. #1
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    flac compression/size discrepancies

    So I was ripping an audio cd to FLAC using EAC and noticed that the percent compression was a lot higher than all the flac files I have downloaded in the past. As an example, a certain track that is about 4 minutes in duration, when ripped from the original cd, ended up being 12mb in size and 72% compressed. Most of the downloaded flac album tracks are usually about 20-30mb and only 20-30% compressed.

    I downloaded the exact same track in flac format and it is 23mb and 46% compressed, which is quite significant. I know there are different compression settings for flac (from 0-8), but from what I read, it didn't seem like the difference could be this huge.

    I did a test with both of these flac files and converted them both to wav files, and the sizes are pretty much identical (maybe about 15 bytes off), which seems to me that my own ripped flac file was just truly more compressed than the other with no loss in data/quality.

    This is the command line I used in EAC: -8 -V -T "ARTIST=%artist%" -T "TITLE=%title%" -T "ALBUM=%albumtitle%" -T "DATE=%year%" -T "TRACKNUMBER=%tracknr%" -T "GENRE=%genre%" -T "PERFORMER=%albuminterpret%" -T "COMPOSER=%composer%" %haslyrics%--tag-from-file=LYRICS="%lyricsfile%"%haslyrics% -T "ALBUMARTIST=%albumartist%" -T "DISCNUMBER=%cdnumber%" -T "TOTALDISCS=%totalcds%" -T "TOTALTRACKS=%numtracks%" -T "COMMENT=%comment%" %source% -o %dest%

    Any ideas on what may be going on here? Is it possible for two flac files of the same song, where one file is twice as big as the other (12mb vs 23mb)? As I stated earlier, most of the download flac files I have are around 25-30mb so to see that this one was only 12mb was a bit shocking. I would appreciate any comments or explanations for this matter! Thanks in advance!

  2. #2
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    Hmm...but I just took an v0 mp3 file and a flac file for the same song and converted them both to wav...and the sizes were pretty close too (with the wav file converted from the mp3 file being 12 bytes less)...shouldn't there be more of a discrepancy since mp3 is lossy?

  3. #3
    Senior Member Wombat's Avatar
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    Quote Originally Posted by nelce View Post
    Hmm...but I just took an v0 mp3 file and a flac file for the same song and converted them both to wav...and the sizes were pretty close too (with the wav file converted from the mp3 file being 12 bytes less)...shouldn't there be more of a discrepancy since mp3 is lossy?
    mp3 replaces content of music it thinks you can┤t hear with noise. When decoded to wav a lossless compressor has problems compressing the noise so in the end the original wav may end at ~ the same size.

    As for your other questions. Decode all files to wav and encode them with the same flac version and setting and start from there.
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  4. #4
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    So are you basically saying depending on the flac version used to encode the flac files, it's possible to have that huge of a discrepancy in file sizes and percent compression for the same song? I have been browsing all the flac files I downloaded and nto wrap one of them are even close to a 74% compressed number. I'm just curious if this is actually possible while maintaining no loss in data. I mean I ripped the track straight from the cd with a flac encoder so theoretically there should be no loss in quality. I just can't seem to wrap my head around the huge discrepancies. I'm sure if I decoded both flac files to wav and then encoded it back to flac with the same flac program, the size will be the same though. I'm not sure that will give me any answers...unless I have misunderstood?

  5. #5
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    Quote Originally Posted by nelce View Post
    Hmm...but I just took an v0 mp3 file and a flac file for the same song and converted them both to wav...and the sizes were pretty close too (with the wav file converted from the mp3 file being 12 bytes less)...shouldn't there be more of a discrepancy since mp3 is lossy?
    No, they'll both decode to the same size because they both represent 44.1 kHz 16-bit stereo. Two files that encode X seconds of music, no matter if they're lossy or lossless, will give you the same amount of data when they're decoded.

  6. #6
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    Compression ratios depend on the audio being encoded. It's not unusual to have tracks in a library that only compress 20%, nor tracks that compress up to 80%.

    Was the CD that you ripped a commercial CD or a CD-R? It's possible that a CD-R could have been burnt from a decoded Mp3 (or other lossy format) file. When it's then re-encoded by Flac you'll get a larger amount of compression than you would with the original data from the CD.

    Try AudioChecker to test files of unknown origin.

  7. #7
    Senior Member Wombat's Avatar
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    Quote Originally Posted by JJZolx View Post
    No, they'll both decode to the same size because they both represent 44.1 kHz 16-bit stereo. Two files that encode X seconds of music, no matter if they're lossy or lossless, will give you the same amount of data when they're decoded.
    Hehe! I did misread this one. I meant flacs of wav and mp3 are ~ the same. Never expected someone asks about differences in wav size between decoded mp3 and original wav

    As for the big difference in filesize there was a point where flac started to detect empty bits very effective and can reduce some files even better as other compressors. So once again, please encode the files with the same flac version and setting.
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  8. #8
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    Quote Originally Posted by JJZolx View Post
    Compression ratios depend on the audio being encoded. It's not unusual to have tracks in a library that only compress 20%, nor tracks that compress up to 80%.

    Was the CD that you ripped a commercial CD or a CD-R? It's possible that a CD-R could have been burnt from a decoded Mp3 (or other lossy format) file. When it's then re-encoded by Flac you'll get a larger amount of compression than you would with the original data from the CD.

    Try AudioChecker to test files of unknown origin.
    My file was ripped from an original commercial cd and I'm pretty sure the downloaded flac file was too. That is why I'm so surprised but the difference in size and compression.
    Is it possible to have this great of discrepancy if the same song was ripped from the same cd, even if the flac encoder and settings were different?

  9. #9
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    Quote Originally Posted by nelce View Post
    My file was ripped from an original commercial cd and I'm pretty sure the downloaded flac file was too. That is why I'm so surprised but the difference in size and compression.
    Is it possible to have this great of discrepancy if the same song was ripped from the same cd, even if the flac encoder and settings were different?
    I wouldn't think so, but you can always re-encode them using the same version of Flac and the same compression setting and compare those files.

  10. #10
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    When you say compare those files, do you mean compare the file size and percent compression? Or is there a software to compare something more detailed?

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