Checking lossless audio with Audiochecker

[sakis21]

This is related to the GITS lossless collection issue, with some tracks considered to be lossless and appear lossy in audiochecker.

So, I checked, with audiochecker, another lossless collection of mine (not uploaded on BBT), 3 albums 2 singles, around 70 tracks in total, and again there were 4-5 tracks that had over 80% probability of being mpeg format. None of them is ripped by me, and they appear to be flac in terms of format name and bitrate (in foobar and winamp).

Can anyone tell me in what ways is it possible for a lossless collection to be uploaded with some tracks of it being lossy?
Is it possible that the original uploader collected the tracks one by one and decided to fill in some missing lossless ones with transcoded from lossy lossless ones or is this a common error of audiochecker?

Another clue is that the unsplit .ape file of one of the 3 albums was checked 100% CDDA by audiochecker, while the split .flac version of the same album had 2 lossy tracks (according to audiochecker).

I also understand that another way to check the true quality of a track is with a spectogram. How is this done exactly (do I check certain freq bands?), and is it really accurate?

[jokli]

I wouldn't trust Audio Checker too much. If you want to judge authenticity by looking at the frequency spectrum along the time, just look at several examples of files you are quite sure they are really lossless and some MP3s. Probably you will notice the difference and learn how to decide whether any given time–spectrum graph corresponds to a lossy file. Nevertheless there are lossy codecs (non MP3) which look very similar to their lossless originals.
One nice tool is the Sonic Visualiser.

Regarding GitS:
With foobar2000 I have created a cue sheet that represents the REPACK version of OST 4 and changed it to use "01 - smooth in the shell (no break disk).flac":

Code: [Select]

REM GENRE Soundtrack
REM DATE 2007
PERFORMER "Yoko Kanno"
TITLE "Stand Alone Complex O.S.T. 4"
FILE "01 - smooth in the shell (no break disk).flac" WAVE
  TRACK 01 AUDIO
    TITLE "Phase Delight"
    INDEX 01 00:00:00
  TRACK 02 AUDIO
    TITLE "Northern Flow"
    INDEX 01 04:10:65
  TRACK 03 AUDIO
    TITLE "Transistor"
    INDEX 01 06:48:47
  TRACK 04 AUDIO
    TITLE "Static Funk"
    INDEX 01 08:01:64
  TRACK 05 AUDIO
    TITLE "Alleyway Sleeper"
    INDEX 01 10:56:34
  TRACK 06 AUDIO
    TITLE "Runaway"
    INDEX 01 11:58:58
  TRACK 07 AUDIO
    TITLE "Banquet Firewall"
    INDEX 01 13:31:69
  TRACK 08 AUDIO
    TITLE "Blur Storm"
    INDEX 01 18:47:20
  TRACK 09 AUDIO
    TITLE "Tundra"
    INDEX 01 22:47:27
  TRACK 10 AUDIO
    TITLE "Net Cafe"
    INDEX 01 26:19:09
  TRACK 11 AUDIO
    TITLE "Black Waltz"
    INDEX 01 30:12:05
  TRACK 12 AUDIO
    TITLE "Decisive Action"
    INDEX 01 31:24:54
  TRACK 13 AUDIO
    TITLE "Rapid-fire"
    INDEX 01 32:55:54
  TRACK 14 AUDIO
    TITLE "Launch Mosaic"
    INDEX 01 34:03:04
  TRACK 15 AUDIO
    TITLE "Smooth Combat"
    INDEX 01 34:42:52
  TRACK 16 AUDIO
    TITLE "Quartz Movement"
    INDEX 01 39:40:42
  TRACK 17 AUDIO
    TITLE "I/O Rain"
    INDEX 01 41:54:54
  TRACK 18 AUDIO
    TITLE "Major's Minuet"
    INDEX 01 45:05:28

The result is almost identical to the REPACK with respect to timing. The lengths differ a bit (some hundred samples; i.e. a few 1000th seconds) from the REPACK due to the imprecise time codes in the cue sheet.

Of course you may use it in your torrent, for example just as an extra for the no break version, which is the original! I think, since the cue sheet version and the REPACK are almost the same, the latter is now obsolete.

Again with foobar2000 and now with the help of the new cue sheet, I then extracted the suspicious track 6 from that no break file and let Audio Checker look at it. It says it's MPEG with probability 73% while the whole no break file is determined to be 100% CDDA. So this shows the same behaviour as you have mentioned it for another album. Looking at the spectrum graph, I guess it's lossless.

[sakis21]

So the SAC OST4 repack had tracks that showed loosy in audio checker, too huh?
About 4, 7 and 9 from Techno Style, if I understood correctly you said that these appeared to be lossy even by checking their spectrum graph?
Anyway, from what you said should we assume that the entire collection is lossy and it was audio checker that was mistaken then?

- EDIT -

^In the last line I meant lossless (*entire collection lossless*)

Anyway thx for the answers. Lets assume for now that my offer is purely lossless.

[jokli]

Yes, both versions, the extracted one from the no break disk and the one from the REPACK are judged as lossy by Audio Checker:


My personal guess is that Audio Checker simply shows a false positive. I think the files are all really lossless.

PERHAPS the tracks 4, 7 and 9 from Techno Style are lossy with respect to the CD.
Another possibility is that they are even lossy on the CD with respect to what the producer created and lossless with respect to what can be found on the CD in the torrent. It could also be that simply the production was done with lossy files.