Is it possible that audiochecker tells some tracks are MPEG?
Yes, that's possible, what I shared are exact copies of the silvers, so it depends :
- of the source they used, that could very well be lossy after all
- of the treatment done to the sound, the work on the sound could result in the cut of some frequencies, which makes audiochecker find lossy files.
To cut short, a file checked as "CDDA" means a lossless file, the sound has all its frequencies intact, so it is considered as lossless (no loss of frequency, therefor no loss of quality). A sound checked as "MPEG" means there was some compression along the way, some frequencies were dropped, therefore the sound is not "complete", it is considered as lossy. MP3 uses the MPEG compression, that's why you can see messages such as "don't share those files as MP3" in the text of some shares. A compression to MP3 or any compressed format is definitive, you can't undo that, so you decrease the quality for good.
Audiochecker gives also a percentage before CDDA or MPEG, 100% MPEG means Audiochecker is absolutely sure, given its criteria, that the file is lossless. 40% CDDA means the software is not so sure, but he bets that it is lossless.
A perfect recording, taken from an original lossless source would give all files with "100% CDDA". It is not the case here; that's most probably because it is not a real copy of the source, but the sound has been modified by the bootleg company. They remastered it in some way. It could be me who modified the sound after ripping the files from the bootleg discs, but it's not the case here, it is a direct copy of those discs.
To get more information you can use the Word document with the freq analysis and spectral views, which gives you a view of the level of the frequencies used. The human ear can hear up to 20.000 Hz or so (some say they can hear more, some less). So a MP3 conversion would cut the frequencies at 16.000 HZ, therefore 20% of the sound is deleted. Here it is not the case, but you can see something like a line around 15.000 Hz which makes Audiochecker (which is only a software analyzing the files with given criterias) a little unsure of the results he gives. Whether the remastering works made this line, or the original source had this "hole" (could be a problem with the equipment, or bad mikes, or something like that), is unknown to us; bootleg companies don't tell what is done to the sound.
In my own opinion, a bootleg still is a bootleg, a product on his own, with its own history, its own artwork, its own trademark sound (for example Gypsy Eye and its crackling sound). Someone dealt with the sound along the way, or not, we don't know. It is different from a RoIo (Recording of unkown origin), because it is at first created to be sold, whereas RoIo's are generally exchanged between the fans (at first, some bootleg companies are avid of an easy "download, cut and paste", but that's another story).
Therefore, the bootleg companies use the sources they have (sometimes they are the only persons to have them, it is not shared elsewhere), and they can play with the sound as much as they want, nobody can't do anything about that. They create a sort of finished product. That's what is shared here !
Therefore, you can't really know what was really done to the sound and by whom (bootleg company, original sharer?) or what (hiss reduction, bad equipment used?).
At least that's my own explanation, but some more skilled people could confirm/correct/complete what I say !
wanna trade ?