Universal MG embed an audible watermark in downloads (article@post#30), Was: FLAC file with artefacts not present on original CD? Options

[mannheim]

This is my first post in these forums.

Can anyone help me guess the source of some audible artefacts in some downloaded music?

I have two FLAC files for the same classical track (Tchaikovsky's 5th Symphony, Markevitch, on a Philips label). One was purchased from Passionato, the other was purchased from UMG's web site. Although both are supposed to be lossless copies of the data on the original CD, the FLAC file from Passionato actually has a clearly audible sort of "flutter" in some quiet, sustained passages. It is not the same as the UMG file. The difference isn't subtle. (Having read the TOS, I did do an ABX test. But it hardly seemed necessary in this case: I got 10/10 without difficulty. I will upload the short samples that I used.)

My guess was that the Passionato download was actually derived from a compressed audio file, converted to FLAC. But I'm puzzled. Compressing the UMG file and then converting back to FLAC did not give me a result that was in any way comparable, whatever compression I tried. The UMG and the Passionato file have exactly the same number of samples, and the difference of the two wave forms has a spectrum which is mostly in the range of about 1000 Hz - 2500 Hz, with very little above that.

Another possibility is that both FLAC files were obtained from some (fairly high quality) compressed source -- say MP3 -- but that the Passionato file was decompressed using software with a bug. I have quite a few FLAC files from Passionato. All the files from UMG labels exhibit this "flutter", with the exception of the most recent one I purchased.

I will edit this post when I have a link to the samples. I'll upload 7 seconds of each of the two FLAC files, and also the difference of the two wave forms (amplified). The difference sounds like fragments of the original tones together with higher "chirps". (I read the TOS concerning differences of wave forms, but I think the difference is interesting in this case.)

Edit: The uploaded FLAC samples are here.

This post has been edited by mannheim: Jul 21 2011, 18:56

[mixminus1]

Hmm, interesting, and I agree with Wombat (edit: and greynol), I think they both come from true lossless masters, as well.

The reason I don't think the Passionato track is sourced from lossy is that, in addition to what Wombat noted about the noise floors, the fluttering is fairly slow, but very rhythmic and consistent, which is usually not the case with fluttering/ringing artifacts in lossy encoding. Yes, those artifacts can be somewhat rhythmic, but they're usually much faster.

I was going to guess wow and flutter (specifically wow) from an analog tape machine, but if this is the release you're referring to, it appears to be all-digital, so that couldn't be the case (and all that hiss would then be coming from the mics and/or preamps).

Odd indeed...was there any liner note info included with the Passionato download WRT the mastering engineers or facilities?

This post has been edited by mixminus1: Jul 21 2011, 20:24

[evereux]

I was going to guess wow and flutter (specifically wow) from an analog tape machine

That was my thought too.

[mannheim]

I was going to guess wow and flutter (specifically wow) from an analog tape machine

That was my thought too.

I do have some entirely digital recordings from passionato.com with the same problem. For example, I have this version of Mahler 9, in FLAC format, and it has the same sort of "flutter" effect (e.g very apparent in the horn phrases at 00:35 to 00:45 in the first movement). For this release, I do not have the corresponding FLAC file from the Universal Music web site (the link above), so I can't make a comparison. But I have listened to the clip of this track that is available on Amazon's MP3 web site. Although the streaming quality of the clip is low, it is good enough to be fairly sure that the flutter is not present.

[Wombat]

One thing i noticed is the noise floor in the delta file looks like noise shaped dither. So one of these recordings must have gone thru some digital processing or downsampling different as the other file.
I wonder if one version was processed to correct the flutter. Imho this is pretty hard to repair. The other way around makes not much sense but who knows!?