CDDA-PE

pre-emphasis in compact disc copy protection

Have you ever wondered why there was no publicly acknowledged copy protection scheme associated with the original Compact Disc launch?

Since when have the record companies been carefree about releasing perfect copies of their master tapes?

I think I have the answer, after four decades of ear splitting treble and no bass from these shiny little discs.

According to my findings, pre-emphasis (50μs/15μs) was not just used for its stated purpose although it may have begun as a legitimate technical specification as is the case with the broadcasting standard CCITT J.17 pre-emphasis option also built into the PCM encoding process [see AES/EBU digital interface standard] when transferring analogue audio to digital. Importantly, the presence of any pre-emphasis EQ curve applied during encoding is supposed to only be for optimising the accuracy of the transfer to digital and must be flagged in the data so that it can be automatically removed upon playback to retrieve the optimised flat response intended.

Instead, I find that the 50μs/15μs pre-emphasis EQ curve was used to “spoil” the playback of the audio by applying the pre-emphasis on encode but not flagging it in the data on the finished discs. In this way, the analogue audio transferred to digital would have the large treble boost prescribed by 50μs/15μs pre-emphasis added upon encoding, without implementing the requisite 50μs/15μs de-emphasis protocol needed to reverse the treble boost for correct flat playback.

This achieved two important things for the record companies - it protected their masters in the sense that they weren’t being issued unaltered and it also ensured an artificially bright playback from what would otherwise, without involving costly and time consuming catalogue wide remastering programs, have been the flat masters on Compact Disc. This hyped up playback is what made Compact Disc really stand out from any consumer format that had preceded it.

The fact that it was technically incorrect playback is not important here - it is the fact that the treble boost associated with 50μs/15μs pre-emphasis vastly increases the interest from the general public in the new format that is important to the record companies.

Consider the fact that Compact Disc 16-bit/44.1 kHz PCM is effectively transparent and would not assist any flat master tape at all in sounding more ear catching to a non-audiophile and you realise the importance of this additional pre-emphasis in the incredible success of the new format.

Convenience is not the only factor in the success of Compact Disc. Had it actually just sounded like a transparent copy of a reel-to-reel tape then why would it be so much more popular than consumer reel-to-reel, the closest to that kind of accuracy and also the poorest selling format of them all? The answer is that people were intoxicated by the new levels of treble detail never before possible with the analogue formats that this stealth pre-emphasis on Compact Disc provides, despite it being a technical and aesthetic abomination.

So, a scramble to protect the master tapes turns into a huge win for the record companies. Even the consumer is happy, overall. Only the audiophiles are left wondering what went wrong.

The good news is that you can restore the correct playback by applying de-emphasis to the spoiled audio on the affected CDs. What you get after de-emphasis is an effectively transparent flat copy of the master tape.

This works on not only original CD catalogues but also much later ones - for example, since the mid-2000s The Everly Brothers Warner Brothers master tapes have all been available on Bear Family (also available in part on Collectors’ Choice Music and Warner Strategic Marketing releases) and all have unflagged pre-emphasis present. Simply apply de-emphasis and you are now in the Everly section of the Warner Brothers vault.

This applies to many other catalogue dumps too - it seems that the major labels allow other people to release their back catalogues en masse so long as they use the spoiled masters the majors provide.

New releases also received this pre-emphasis spoiling, not just back catalogue items. For example, Michael Jackson albums on CD have pre-emphasis spoiling present through at least HIStory in the mid-90s.

Some early CDs also have flagged pre-emphasis - this is on top of the spoiling pre-emphasis already on the original digital transfer and so needs removing otherwise the playback is too bright for anyone to listen to. This has been a major part of the confusion that has surrounded pre-emphasis on CD for the end user since ripping discs became possible. Once a flagged disc has been ripped, de-emphasis needs to be applied just to get to the underlying layer of unflagged pre-emphasis. De-emphasis must be applied a second time to remove this “copy protection” layer and reveal the flat master transfer.

This was an industry wide ploy to protect the masters and was still affecting some back catalogue releases into the 2000s and may even still be around today, believe it or not.

Not all discs are affected but many are - the basic rule of thumb is that if the CD contains a flat transfer of the original master tape then it is likely to have the spoiling layer of unflagged pre-emphasis present as a form of copy protection. This applies to the original discs in general but also still applies to some later CD releases as well.

In 2001, the record companies introduced Copy Control - a code based copy protection scheme for Compact Disc aimed at inhibiting the ripping of the audio from the disc.

Interestingly, the logo for Copy Control is a nested variation on the original SONY DIGITAL AUDIO DISC logo from c. 1980 which itself then appeared on much of the mostly digitally sourced CBS product in the United States from c. 1984 to c. 1994.

My guess is that this mystery symbol on CBS product actually indicated “spoiled master” - i.e. it has unflagged pre-emphasis added and this was SONY’s way of tracking market acceptance of this spoiling protection scheme for the industry as a whole. That is to say, all the record companies were spoiling the playback with pre-emphasis but only SONY were secretly tracking it with a publicly visible logo.

In summary, record companies were in a bind back in 1982 and needed a way out of simply giving away all their master tapes on the transparent new format - Compact Disc. They used a trick that just so happened to be available to them in the PCM format that had been developed and it turned out to be incredibly effective, without any extra work being necessary to implement it.

So, for any Hi-Fi enthusiasts left at this point, armed with this knowledge hopefully you will finally get to enjoy the true promise of Compact Disc Digital Audio at home - “Pure, perfect sound forever…”