A NEW PROBLEM REGARDING CD MASTERS

If you are producing a CD, this is very important information concerning the production master that you deliver to your manufacturer.

All CD plants can accept a Red Book Standard CD-R as a production master. The problem with music on CD-R has always been that it contains an enormous amount of errors. When CD plants first began accepting CD-Rs it was very difficult to cut a CD-R that would meet the CD plant's standards. That is when Sonic Solutions became the standard in mastering software, because a CD-R master burned on a Sonic Solutions system (called a 'PMCD') was absolutely as low error rate as possible.. These PMCDs were burned on a specific Sony writer at 1x speed.

Unfortunately, rather than maintaining a high standard, the CD plants lowered their standards to the point where you have to deliver an almost unplayable CD-R for it to be rejected by a plant. This is not good news, as the CD's made from high-error CD-R masters will be more unreliable for playing on car players, boom boxes etc. and will have a lower sound quality. Consequently Sonic has maintained their status as the best mastering software, as a 'native-burn' Sonic PMCD is still the lowest error Red Book Standard audio CD-R. But now we have a new problem.

It is still important that audio CD-Rs to be used as production masters be cut at lower speeds. For instance the current Sonic soundBlade mastering system as used as DES cuts at 4x speed. However, CD-R manufacturers are continually modifying their dyes to be optimized for the fastest CD burner speeds. The result of this is that the last manufacturer who made CD-Rs for lower speed burns, Taiyo Yuden, has now scaled down that facility and has discontinued those discs. Mastering rooms who have already tried the new Taiyos report having to burn 5 or more masters before getting one with acceptable error rates. Even burning at 8x results in unacceptable errors. And it has been proven that anything approaching 10x speed definitely reduces the sound quality.

But fortunately there is a solution. The DDPi, as described in our blog entry DDPi - The New Preferred Master for CD Replication, is a completely error-free master. Even though in most cases it is delivered to the CD plant on a data CD-R or DVD-R, this does not affect the quality of the DDPi. The reason is, the method in which data is written to a CD-R is completely different from the method used to burn an audio CD-R. As we said, even the best audio CD-R has a lot of errors. But data CD-Rs are written in such a way that any bad sectors on the CD-R are skipped, and after the data is written a checksum is performed, which verifies that what was written to the CD-R or DVD-R is bit-accurate to the files it came from.

So once again we are emphasizing the importance of DDPi as a production master. DES will provide our clients with info on the best CD plants to use, as not all can accept DDPi.

Again for more info on the DDPi read our entry DDPi - The New Preferred Master for CD Replication.

DDPi - The New Preferred Master for CD Replication

The DDPi (Disc Description Protocol image) is now acknowledged as the superior production master for any optical disc medium - CD, DVD or Blu Ray. The DDPi is an absolutely error-free master, which creates a superior sounding CD in the case of audio, and also creates CDs that are more reliably played by cheap CD players, boom boxes, car players etc.
Originally just DDP, it has actually been around for more than a decade, and has been the standard in video for that long. It also has been in use in audio CD mastering and replication, but on a much smaller scale. The DDP breaks the audio, subcodes, TOC and metadata down into separate elements; five or six files total in the file set. It was originally delivered on an 8mm video cartridge created by a machine called an Exabyte. The downside was it required a specific, costly machine at both the mastering room and the CD plant. And it was a mechanical tape cartridge, which can fail. So enter the future, and for some, the present: DDPi. DDPi contains all of the elements of a DDP Exabyte tape, but it is written directly to a hard drive in the mastering room and can then be delivered to the CD plant on a data CD-R or DVD or if available it can be uploaded directly to a CD plant's server. For your reference, DES will upload the DDPi along with our DDPi player which will allow you to listen to the master, check CD-TEXT and ISRC's, and burn your own CD. A huge advantage to this is that you will be using the exact DDPi that we will be sending to the plant.
The only downside, if you want to call it that, is that you have to use a cutting edge mastering room that understands and can create a DDPi file set, like DES Mastering (www.desmastering.com) for instance, and you have to use a CD manufacturer that can utilize the technology, which coincidentally DES can steer you to.

Stem Mixing

Mixing to stems has been common practice in sound for film and video for decades, but it is relatively new to the world of music production. Many people still don't comprehend that the mastering engineer cannot separate elements in a stereo mix and effect just that one element. For instance if he wants to brighten up the vocals in a stereo mix, everything else in the same frequency range will be brightened also. But if the mastering engineer has stems to work with he has a lot more flexibility and the result can be a much better finished product.

Stems are stereo (or mono) subgroupings of instruments or vocals. For example, the most common stem mixes have a stereo instrumental stem and a stereo vocal stem. When these two stems are set to unity gain (no volume boost or cut) and played through a common stereo output, you should have the complete stereo mix as the mixing engineer/producer intended it. But now if the mastering engineer needs to brighten up the vocals for instance, or thinks the guitars have too much midrange, then he can work with one stem without affecting the other. You might also have a case where the bass has been separated out to a mono stem of its own, so the mastering engineer can compress or eq it independently of everything else.

Stem mixing is really very simple. You don't do anything different until you're ready to bounce your mix. Mix as you normally would, get all of the instruments and vocals balanced, eq'd, panned and f/x'd until you're happy with the mix. Then mute all of the vocals and bounce your mix. You now have the instrumental stem. Then, unmute the vocals, mute everything else, and bounce again. You now have the vocal stem. If you load the two stems back in, set them for exactly the same start time, and play them both through the stereo output, voila! You are hearing your stereo mix just as you wanted. If you have done things correctly, listen to the instrumental stem and you will hear that all of your automated fader moves, f/x etc. have been printed with that stem. You should hear no vocals, vocal reverb, echo or anything else related to the vocals. Likewise if you listen to the vocal stem there should be no hint of instruments or instrument f/x.

So you see it would be the exact same procedure if you wanted to separate out bass, background vocals, drums, whatever. You just mute everything else in the mix except those elements and print. But the mastering engineer would prefer you keep it as simple as possible, the ideal being an instrumental stem and a vocal stem as in the example above. Don't distract the mastering engineer by delivering too many stems in one song so that he is suddenly having to listen like a mix engineer and not a mastering engineer (two VERY different ways of listening, btw).

If you are mixing through an analog console with analog f/x, you need to be very conscious of processor noise. When you are printing your vocal stem, you should mute all f/x processors that are dedicated to instruments only, or if you have dedicated returns for instrument f/x then those should be muted. Otherwise you will be printing the noise from your instrument f/x processors onto the vocal stem, and then you will get the noise again when you print the instrumental stem. Although it may seem like a minor detail, you should do the same when you print the instrumental stem regarding the vocal f/x returns. Even on loud tracks, every little bit of noise you can eliminate will make a difference in the final product.

In the hip-hop world, delivering stems for a single can make your life much easier. All you need to deliver is the instrumental and vocal stem for each song. Now the mastering engineer can add the two together for the club version, mute the bad words on the vocal stem for the radio version, instrumental stem only for instrumental version, vocal stem only for acapella version. Too easy. (Or save a little money and do a clean vocal stem yourself if there are a lot of words that need to be muted).

Make sure you talk to your mastering engineer before you deliver stems. Not all mastering rooms are as technically hip and savvy as DES Mastering (shameless plug), so you shouldn't assume that they can work with stems.

Master, Master, Who's Got the Master?

There's a lot of confusion concerning what a 'master' is. One problem is, too many things are called masters. If you have a 'master', hopefully it will be labeled with one of the following terms. Or if you are in production, and you want to do yourself, your client and anyone else down the production chain a huge favor, learn and use these terms. For these purposes we'll talk about stereo only. Surround opens a whole different can of worms. Here we go!

MULTITRACK MASTER, TRACK MASTER

This is the master containing the unmixed tracks from the recording session. They range from 2 to 32 tracks in analog tape formats, up to 48 tracks in digital tape formats, and 128 tracks and beyond on computer-based systems. On modern track masters, each instrument and voice is still on a separate track. On track masters from around 1967/68 and before, you would have two, three or four tracks of combined or compiled (comp'd) recordings. Say if you had the final 4-track master from Sgt. Pepper, on those four tracks you might have all of the Beatle's rhythm section on one track, the London philharmonic on a second, a percussion section on a third, and all of the Beatles vocals on the fourth. Regardless of the number of tracks, these masters have to be mixed to stereo (or mono) before you proceed to mastering and manufacturing. They can be analog or digital reel-to-reel tapes of varying sizes, audio cassettes, VHS or Hi-8 video cartridges, and these days thumb, USB or Firewire drives, data CD-Rs or DVDs.

STEM MASTER

Mixing audio in stems has been commonplace in the film and video industry for decades, and is becoming increasingly popular in music production. Stems are stereo or mono subgroup mixes that are then combined for the complete stereo mix. In music for instance you could mix a stereo vocal stem, a stereo instrumental stem minus bass, and a mono bass stem. This would allow the producer to easily create a vocal up version for radio, edit the vocal for a clean version, pump up the bass for a club version etc. In mastering, stems allow the engineer to process and control the individual stems rather than having to process the entire mix. Stem masters could be any of the same formats as the track masters above.

MIX MASTER, MIXES, MIX FILES, BOUNCES, BOUNCE FILES, SOURCE MASTER (in mastering terminology)

These contain the stereo mixes that have not been edited or mastered. These can be various sizes of analog or digital reel-to-reel, analog cassette tape, VHS, Beta or Hi-8 video tape, DAT tapes, audio CD-Rs, or folders containing audio files on data CD-R, DVD or any form of hard drive.

For people who record and mix 'in the box': Do not be a lazy engineer. Your individual tracks in your session folder should have proper file names, "Kick", "Snare" etc., not "Track 1", "Track 2"... Your mixes should be in one folder labeled as "Mix Masters" etc.

EDIT MASTER, BANDED MASTER, SEQUENCE MASTER, SEQ MASTER

In the analog days of vinyl, this referred to an analog mix master tape that has been sequenced and topped & tailed (noise before and after each song edited out), timed leader tape has been inserted between tracks for proper spacing, and leader tape has been added to the head and tail of the reel. It also implies that any inner-song editing has been done. In the analog days we would say these tapes have been 'prepped', meaning the tape has been prepared for the cutting room. Unless otherwise noted, this master has not had any further processing such as eq, compression or limiting, which was done at the lathe as the lacquer was cut. In today's world, mastering engineers prefer that you do not top or tail your mixes, leave a second or two of noise before and after the audio.

In the digital age, a BANDED MASTER has a new meaning. Many artists want to have some or all songs on their album crossfade between each other, have no space between tracks etc. But of course this can cause problems in the age of downloads since the ending of a song that crossfades into another song will just suddenly chop off if you download the first song only. Or if you download the second song, you hear the end of the first song fading out as the song you wanted starts. So many artists have their mastering engineer create a 'banded master' which has a basic 2 seconds or so of silence between songs. They will use this as the source for online content so the songs have clean in's and out's. This also allows them to suggest purchasing the CD if the listener wants to hear the album the way it was really intended. Unlike the analog version, this type of banded master would be implied to have all mastering processing applied. These banded masters can be on any of the media described in the next category.

PRODUCTION MASTER, PRE-MASTER, EQ MASTER, EQ AND LIMITED MASTER, PMCD, REFERENCE MASTER, GOLD DISC MASTER, DDP, DDPi

A master that has any of these labels would be assumed to have all mixing, editing, sequencing and masteering applied and is ready for manufacturing as is. Some of these need further explanation:

PRODUCTION MASTER, PRE-MASTER, EQ MASTER, EQ AND LIMITED MASTER - The standard media that manufacturers can or could accept that would have one of these labels would be analog or digital reel-to-reel tape of varying sizes, VHS, Beta, Hi-8, and 3/4" U-Matic video tape, audio cassette tape, DAT tape, red-book standard audio CD-R, and now some manufacturers will accept production master audio files on data CD-R, DVD, any type of hard drive or as uploads to a server. 'EQ Master' and 'EQ and Limited Master' are old-school terms for labeling production master reel-to-reels that were prepped for the cutting room. If your mastering guy uses one of these terms you can be pretty sure he's been around the block.

PMCD, REFERENCE MASTER, GOLD DISC MASTER - These would only apply to a CD-R. The definition of PMCD has changed. Originally, this meant 'Pre-Master CD'. This was a revolution in CD manufacturing that was developed by Sonic Solutions and allowed CD plants to cut glass (explained below) directly from a CD-R, eliminating a very expensive step that will be explained later. The Pre-Master CD was a CD-R that could only be created on Sonic Solutions mastering systems and contained a data burst that fed the TOC (table of contents) timecode information into the glass mastering program independent of the audio. Probably no, or at least very few, CD plants can use Pre-Master CDs any longer, as the CD burners that Sonic needed to create them have been obsolete for about 15 years. And now CD plants can cut glass from ordinary red-book standard audio CD-Rs. These audio CD-R production masters were originally referred to as a Reference Master or a Gold Disc Master (even though the disc may be silver or green). Some still use those terms, but increasingly they are referred to as a PMCD, now meaning 'Production Master CD'. A CD-R with one of these labels would normally be for CD replication, but often production masters for vinyl records or in the days of cassettes would have the same label. If you have a master that is labeled 'PMCD', there is really no way of telling which type it is if you don't have a Sonic Solutions system with the proper CD drive. But never fear, a Pre-Master CD will play on a normal player, and can be used by a CD plant, just like a current Production Master CD.

DDP - The DDP (Disc Description Protocol) is acknowledged as the superior production master for any optical disc medium - CD, DVD or Blu Ray. The DDP is an absolutely error-free master, which creates a superior sounding CD in the case of audio, and also creates CDs that are more reliably played by cheap CD players, boom boxes, car players etc. The DDP breaks the audio, subcodes, TOC and metadata down into separate elements, and is delivered on an 8mm video cassette created by a machine called an Exabyte. The downside is that it is still a mechanical tape cartridge, which can fail, and it requires a specific, costly machine at both the mastering room and the CD plant. So enter the future, and for some, the present:

DDPi - DDPi is a 'Disc Description Protocol image'. and is the new standard in production masters for any optical disc, including audio CDs. It contains all of the elements on a DDP Exabyte tape, but it is written directly to a hard drive in the mastering room and can then be delivered to the CD plant on a data CD-R or DVD or it can be uploaded directly to a CD plant's server. The only downside, if you want to call it that, is that you have to use a cutting edge mastering room that understands and can create a DDPi file set, like DES Mastering (www.desmastering.com) for instance, and you have to use a CD manufacturer that can utilize the technology, which coincidentally DES can steer you to.

The reason Sonic Solutions (now SonicStudio) workstations, as used by DES, have been the mastering industry's standard for 20+ years is not only because of their superior sound quality but because Sonic writes the absolutely lowest error PMCD compared to any other system. However, you would probably be shocked to see how many errors even these comparatively low-error masters have, and these translate directly to your manufactured CDs. The thing is, a CD player has a certain amount of DSP (digital signal processing) allocated for error correction. The amount of DSP being performed will directly affect the sound quality of the playback. So the fewer errors on the CD, the better the sound. That is why real mastering rooms use very specific software and burners. If the person doing your mastering is using standard off-the-shelf CD burners and software, you are losing sound quality. So to emphasize the advantage of DDPi, it is an error-locked system, meaning it is either 100% accurate or 100% fail. If it works, it is absolutely error-free, yielding the best sounding CDs possible. But rest assured that even if you are already using a plant that can only accept Production Master CDs, DES Mastering can provide you with the best quality master possible. OK, enough commercials; onward, through the fog!

Now things get a little tricky, because we have a difference in terminology between Europe and the U.S. In the U.S., what we do at DES (eq, compression, limiting, song sequencing, spacing etc.) is called 'mastering'. In Europe, this is called 'pre-mastering', and 'mastering' means that you are creating a part that will be used in manufacturing; cutting lacquer for vinyl, cutting glass for CD replication (we'll get to that) etc., and this is also called mastering in the U.S., which causes some confusion.

PCM-1610, PCM-1630

Before Sonic created the Pre-Master CD, anything going to CD replication had to be on either a Sony PCM-1610 or PCM-1630 formatted tape. Simply put, these were like gigantic DAT machines with a couple of extra analog data tracks where timecode and pq subcode info was put. The converter itself was probably 30"wx24"hx30"d and weighed 100 lbs. or so. Rather than a tiny DAT tape the digital audio was recorded onto a professional 3/4" U-Matic video tape, which required an enormous video deck. If I remember correctly, the cost of the converter with the video deck was around $25-$30,000.00. Of course smaller mastering rooms couldn't afford this, so some CD plants would allow Production Master DATs that they would then format to their 1630, for an extra fee of course. If the only master you have is one of these U-Matic tapes, there are still mastering rooms that have a 1630 system and can get your material onto a more usable format, but you would be advised to do this asap. If you need this contact us at george@desmastering.com and we will refer you to the proper people.

GLASS MASTER

Boy, does this cause a lot of confusion. With only the rarest of exceptions, glass mastering is only done at your CD plant. A few of the super high-end (and priced) mastering facilities may cut glass, but they are few. Even a lot of people who consider themselves mastering engineers get it wrong and will call the PMCD (or Reference Master or Gold Disc Master, as you now know) they create a Glass Master. Getting back to the terminology thing; the CD plant uses the European terminology - the processing and assembly done by DES for instance to create a PMCD or DDPi would be 'pre-mastering', cutting the glass at the plant from this would be the 'mastering'. This causes confusion when a plant says that mastering is included in their pricing. What they are talking about is cutting the glass master. Their price does not included pre-mastering.

The glass master is a large glass disc approx. 240mm in diameter that is painted with photo-resist. Then the digital audio from the PMCD, DDP, DDPi or PCM-1610/1630 is photo etched onto this using an LBR (Laser Beam Recorder). Stampers are then created from this and the photo-resist is peeled off the glass which is then highly polished to be used again. So the CD plant will only have a limited number of glass discs that are used over and over. This is the CD equivalent of cutting lacquer for vinyl records.

A note about production masters for download-only releases:

At the very least, this should be a PMCD. Online stores such as iTunes and CD Baby will not allow you to upload your own mp3s or AACs. They want the full resolution, CD-quality audio files. That way, not only can they create the best quality compressed files with their own CODECs, but as technology improves, like when iTunes went to iTunes+, they can create a new set of compressed files from your full-resolution upload. Hopefully, as connection speeds increase and storage gets cheaper, we will be downloading full CD-quality music, or even better.

As we've said before, you should NEVER accept an mp3, AAC or any other data compressed file as a mix master or production master. See our entry "Audio Production in the Age of mp3 and AAC" http://desmastering.blogspot.com/2009/09/audio-production-in-age-of-mp3-and-aac.html.

I intended to include a list here covering a question that we mastering guys hear all of time time; "I've found this (fill in the blank) type of tape/disc from an old session. What could this be?", but this has already gone longer than I expected. I'll do that next entry.

What is Acceptable as a Master?

As the home recording 'revolution' continues, we are seeing more and more people charging for professional audio services but who apparently have no idea about standards that have to be met in order to assure the best audio quality, and what to give their clients so they can proceed to post-production, mastering and manufacturing. There is a disturbing trend, especially in the hip-hop community, of studios, producers and so-called mastering engineers delivering mp3s as masters.

PLEASE MAKE NOTE - MP3 IS BARELY ACCEPTABLE AS A CONSUMER FORMAT. IT IS NOT ACCEPTABLE AS A MIX MASTER, PRODUCTION MASTER OR FOR ANY OTHER PROFESSIONAL APPLICATION!

The only thing in professional production that mp3 is used for is as a quick reference that can be uploaded for a client to approve a mix, an edit or a revision etc. Also, most stadium and arena music comes from mp3, but that is hardly a critical listening environment.

If you mix to a digital recording system, when you leave the studio you should have your mixes in as high resolution digital format as possible. Refer to our blog entry of Sept. 15, 2009 "Audio File Formats, Sample Rates and Bit Depth" for a detailed explanation. But in brief, your mixes should be .wav, .aif or .sd2 audio files of at least 24 bit resolution and at the same sample rate your session was tracked at. In other words no sample rate conversion should have been performed. Also, be sure you get your 1st generation, unprocessed mixes. That means no normalizing, fades, edits or any other process has been applied. You might also have a folder of Edit Masters which have fades & edits (normalizing shouldn't be done in any case), but for mastering you want the totally unaffected mix masters.

It's a good idea for you to take a hard drive to the studio and have them put your high res audio files there, or the studio may have priced a drive in your package, but you should also have them create one or more data CD-Rs or DVDs containing your mixes. I've seen it before; artists who think they've done the right thing by storing all of their mixes and sessions on a hard drive, only to have the drive fail. Having them on a hard medium like CD-R or DVD is the safest backup. Of course you also want the studio to provide you with an audio CD-R reference disc so you can easily proof your mixes, but for your archive and for mastering, post production etc. they should be high resolution .aif or .wav or .sd2 audio files.