I/O: OUTPUT

MP3/AAC CODEC CHECK

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The primary distribution method for the majority of artists today is digital distribution and streaming. In most cases, the format delivered to the consumer is a lossy file format.

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LOSSY FILE FORMATS

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Unlike lossless file formats (FLAC, ALAC, etc.) which use linear prediction and run-length encoding to reduce file size, most lossy file formats utilize perceptual coding to discard audio components that are considered beyond human perception. In effect, the audio signal is encoded using inexact approximations. The lossy data compression substantially reduces the bit rate and, therefore, file size when compared to the original uncompressed file (WAV, AIFF). Because of the reduced bit rate and file size, lossy formats are an efficient means for digital distribution and streaming. MP3 and AAC are the most widely used lossy formats.

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PEAK LEVELS

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Lossy encoders introduce noise during encoding (defined as approximation error) which can increase peak levels beyond the peaks of the original uncompressed file (WAV, AIFF), sometimes resulting in clipping (or peaks exceeding 0 dBFS and/or 0 dBTP). In general, the lower the bit rate of the encoder the higher the increase in peak level.

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TEST ENCODE/DECODE

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All WAV production masters at Mindtree undergo a test MP3 and AAC encode/decode to ensure that peak levels do not clip during lossy encoding and decoding. The test MP3 file is encoded from the 3244 WAV master with the LAME MP3 codec at 320 kbps constant bit rate (CBR). The test AAC file is encoded from the 3244 WAV master with the Apple AAC codec from iTunes for Windows at 256 kbps constrained variable bit rate (CVBR). This codec is the Windows version of the iTunes Plus codec, which is the default file format for iTunes and Apple Music. Lower bit rate (192 kbps, 128 kbps, etc.) MP3 and AAC files, as well as other lossy file formats, are not tested and may exhibit peaks exceeding 0 dBFS and/or 0 dBTP.

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REFERENCE FILES

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After completion of the MP3/AAC codec check, an email will be sent containing a Dropbox link for downloading a set of MP3/AAC reference files. A Dropbox account is not required.

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Secure File Download Instructions

1 Click on Dropbox link in supplied email.

2 Enter provided secure file download password in link password field and click Continue.

3 Click on Download button.

4 Select either Direct download or Save to my Dropbox (Dropbox account needed for this option) to transfer all folders and files. Direct download saves ZIP files in your device's default downloads folder. The ZIP files should be unzipped and the files in the extracted folders used for reference. Save to my Dropbox saves the folders and their contents to your Dropbox and downloads the folders to all of the computers linked to your account.

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MP3/AAC REFERENCE FILES

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All mastering projects include the following MP3/AAC reference files:

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320 MP3 Reference Files

320 kbps/44.1 kHz MP3 CBR (LAME MP3 codec) reference files for master approval. These files should not be utilized as production masters for digital distribution and streaming.

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256 AAC Reference Files

256 kbps/44.1 kHz AAC CVBR (Apple AAC codec) reference files for master approval. These files should not be utilized as production masters for digital distribution and streaming.

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METADATA

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Optional metadata may be embedded in an MP3 or AAC file through the use of ID3 tags.

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ID3 Tags

An ID3 tag is a metadata container stored within an MP3, AAC, or other digital audio file. The tag consists of a set of frames located at the start of the file, each one capable of storing one piece of metadata. 83 types of frames are defined in the current ID3v2.4 specification; however, most media players only display a subset of this information. ID3 metadata containing Artist Name, Track Title, Album Title (if applicable), Track Number (if applicable), Year, Genre (one of 192 selections), and ISRC identifier (optional) are encoded on all MP3 and AAC reference files at Mindtree.

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Cover Art

ID3 tags allow for the inclusion of album cover art. The following specifications are recommended for cover art images:

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File Type:        JPEG (.jpg, .jpeg)

Color Mode:    RGB/8-Bit

Resolution:      300 ppi (pixels per inch)

Dimensions:    4.724 in. x 4.724 in.

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Album cover art, if provided, is encoded on all MP3 and AAC reference files at Mindtree.

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MASTER APPROVAL

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Upon approval of the reference files, a set of masters is created.

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WAV MASTER CREATION

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WAV masters are utilized by digital distributors and digital delivery platforms for encoding to lossy and lossless formats.

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2496 WAV MASTERS

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24-bit/96 kHz WAV production masters are created directly from the 3296 WAV masters through the use of proper 24-bit dither.

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2444 WAV MASTERS

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24-bit/44.1 kHz WAV production masters are created directly from the 3244 WAV masters through the use of proper 24-bit dither.

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1644 WAV MASTERS

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16-bit/44.1 kHz WAV production masters are created directly from the 3244 WAV masters through the use of proper 16-bit dither.

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THE DIGITAL EP/ALBUM: METADATA

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WAV production masters produced at Mindtree do not include embedded metadata. Although WAV metadata tagging is possible through some software applications, the reality is that very few applications or media players can read or display all forms of WAV metadata. And it is the sheer number of available WAV metadata formats that makes any kind of unified standard difficult to achieve. Implementations include LIST INFO, Broadcast Audio Extension (bext), three different versions of ID3v2 tags, iXML, Adobe's XMP, and from radio broadcast Cart Chunk, in addition to the Broadcast Wave Format (BWF) ISRC specification (aXML). Most importantly, your digital distributor will require you to manually enter metadata information to accompany your WAV masters when they are submitted for production. The digital distributor or digital delivery platform then encodes the metadata on the distribution formats.

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THE DIGITAL EP/ALBUM: ASSEMBLY

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The consumer delivery format for the digital EP/album is a collection of individual tracks, usually (but not exclusively) in a lossy file format. These tracks are encoded for distribution by the digital distributor or digital delivery platform from the provided WAV masters.

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Sequencing

The sequence (or order of tracks) is determined by assigning a track number to each track.

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Gaps

The gap (or pause between tracks) is created by adding a space to the end of the previous track. Thoughtful spacing, in conjunction with sequencing, can help determine the pacing of the EP or album.

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Gapless Playback

Gapless playback is defined as the playback of consecutive audio tracks without pause. Lossless formats are inherently capable of gapless playback, including the use of crossfades (or the simultaneous fade-out and fade-in of two adjacent tracks). Gapless playback of lossy formats, on the other hand, has not been implemented consistently across different codecs and media players. This is due to the fact that lossy codecs add a small amount of space at the beginning (defined as encoder or decoder delay) and end (defined as padding and only applicable during encoding) of each track. Some codecs and media players compensate automatically for the additional space, while others do not. It is, therefore, recommended that gapless playback of lossy formats be avoided.

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QC

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Program Audition

All WAV masters are auditioned in real-time before being approved as delivery masters.

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VINYL PRE-MASTER CREATION

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MASTERING FOR VINYL

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With the destination format being uniquely analog, the requirements of a vinyl pre-master differ from those of a digital master. One of the distinguishing features is that the loudness of a record is not determined by the absolute level of the digital pre-master. Instead, loudness is dictated by the side length and the amount of bass content. Shorter sides with less bass content have the potential to be louder than longer sides with more bass content. Likewise, shorter sides have the potential to contain more bass than longer sides. So, if you want a loud record with a healthy amount of bass you will be constricted to shorter side lengths.

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In addition, there are physical restraints imposed by the cutting head when the master disk is cut by the cutting engineer. Excessive limiting can lead to distortion on the cut, as can sibilance. That being said, I normally reduce limiting (generally to not more than 1-2 dB of gain reduction) or remove it altogether on the vinyl pre-master. And de-essing may be added to control sibilance.

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ASSEMBLY

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The assembly process begins by exporting the vinyl optimized masters as 3296 WAV files. These files are in turn dithered to 24-bit and exported as 2496 WAV files. The 2496 WAV pre-masters are then imported into the PQ editor for sequencing. One thing to be aware of concerning sequencing is that the high frequency response of a record diminishes as the grooves become shorter toward the center, and excessive high frequencies may lead to inner groove distortion. Therefore, it is recommended to place louder, brighter tracks on the outside grooves and quieter, less dynamic tracks on the inside grooves.

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Vinyl Pre-master Timing Guidelines

The timing guidelines listed below are recommended maximum program times per side:

 

7”        Single        45 RPM                  3:00-3:30

12”      Single        33 1/3 RPM        10:00-12:00

12”      LP              33 1/3 RPM        16:00-20:00

12”      Single        45 RPM                  6:00-8:00

12”      LP              45 RPM              12:00-14:00

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These are general guidelines. Be sure to check with your cutting engineer and/or record manufacturer for their exact specifications.

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VINYL PRE-MASTER FORMAT

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The emerging standard vinyl pre-master format consists of two 2496 WAV files (one each for Side A and Side B). A PQ sheet containing track timings is included. The delivery master is termed a pre-master, since the actual production master for record pressing is the master disk produced by the cutting engineer.

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QC

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Program Audition

All WAV vinyl pre-masters are auditioned in real-time before being approved as delivery masters.

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CD PRE-MASTER CREATION

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CD BASICS

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The CD-DA (Compact Disc-Digital Audio) is an optical disc format which stores 16-bit/44.1 kHz PCM audio. The Red Book standard defines the specifications of the format.

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When released in 1982, the CD had a maximum playing time of 74:00. Most CD replicators now allow a playing time of up to 79:48. The audio may be separated into a maximum of 99 tracks, with the minimum length of each track being 4 seconds. The pause between two tracks (known as the pregap) can be specified but is not required nor used extensively anymore. Optional subindex markers used to mark certain positions inside a track are almost never utilized.

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SUBCODE DATA

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In addition to digital audio, the CD contains subcode channel (also known as subchannel or channel) data, which is used to control addressing and playback of the CD. There are eight subcode channels identified by the letters P, Q, R, S, T, U, V, and W. Both the P and Q subcode channels provide timing information. The P subcode channel is a "pause music" flag and identifies the start of a track. Many CD players ignore the P subcode channel and utilize only the Q subcode channel. The Q subcode channel contains the CD's Table of Contents (TOC), UPC/EAN code, and ISRC identifiers for each track. The R - W subcode channels are unused except for the embedding of CD-Text information.

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METADATA

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The Red Book standard allows for optional metadata to be embedded in the subcode of the CD.

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UPC/EAN

The Universal Product Code (UPC) barcode is a global identifier associated with a retail product. In Europe and other parts of the world, the product code is referred to as the International Article Number, formerly known as the European Article Number (EAN). The UPC/EAN code is also referred to as the Media Catalog Number (MCN). Although optional for CD, the UPC/EAN must be provided prior to mastering if you would like it encoded on the CD pre-master. The UPC/EAN cannot be added later without creating a new pre-master. UPC barcodes can usually be obtained for a small fee from your CD replicator or digital distributor. Learn more about obtaining UPC barcodes.

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ISRC

The International Standard Recording Code (ISRC) is the international identification system for sound and music video recordings. Each ISRC is a unique and permanent identifier for a specific recording (not the composition or lyrical content), independent of the format on which it appears. Different recordings, edits, and remixes of the same work require their own ISRC. ISRC identifiers are used by music download/streaming sites and performance rights organizations to identify recordings for royalty payments. Although optional for CD, ISRCs for each track must be provided prior to mastering if you would like them encoded on the CD pre-master. ISRCs cannot be added later without creating a new pre-master. ISRCs can usually be obtained from your CD replicator or digital distributor at no cost. Learn more about obtaining ISRCs.

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CD-Text

CD-Text, an extension of the original Red Book standard, adds the ability to store information about the performer and album as embedded metadata on the CD. CD-Text metadata containing Album Artist, Album Title, Track Artist, and Track Title are encoded on all CD pre-masters at Mindtree.

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Contrary to popular belief, only a limited number of CD players actually display CD-Text. These include certain audiophile grade standalone CD players and some car stereo CD players. Virtually no media player, including iTunes, can display CD-Text without the addition of optional extensions.

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Gracenote

Although not encoded on the CD itself, Gracenote metadata provides artist and album information to compatible media players when a CD is inserted into the CD/DVD drive. Gracenote accomplishes this by maintaining and licensing an Internet accessible database, formerly known as CDDB (Compact Disc Data Base), containing metadata about the content of submitted CD titles. Several media players, including iTunes, utilize Gracenote to provide artist, title, and other information for CDs which have been submitted to the database. When iTunes (or another compatible media player) is launched on an Internet accessible computer and a CD is inserted into the CD/DVD drive, Gracenote queries its database to find a match to display pertinent information.

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CD information should be submitted to Gracenote using a replicated CD, not a PMCD or Reference CD. For this reason, submissions to Gracenote are not normally made by the mastering engineer as part of the mastering process. Follow the steps below to submit your CD information using iTunes:

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1 Launch iTunes on an Internet accessible computer and insert a replicated CD into the CD/DVD drive.

2 Click No when asked to import the CD.

3 Right click on the first track name (Track 01) and select Song Info.

4 In the pop-up box in the Details tab enter Song Name, Artist Name, Album Name, and Release Year, and select a Genre from the drop-down menu.

5 Click on the right arrow button to advance to the next track and continue entering details.

6 Repeat process until all tracks have been titled and then click OK.

7 Click on the Options gear icon at the top right and select Submit CD Track Names... A pop-up box will display when the submission to Gracenote is complete.

8 Wait 2-3 days, launch iTunes, and re-insert the CD into the CD/DVD drive. Then click on the Options gear icon and select Get Track Names. This clears the local cache and performs a re-query to indicate that the CD information is now provided by Gracenote.

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ASSEMBLY

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The CD format provides extensive assembly options. CD assembly is performed in the PQ editor.

 

The 16-bit/44.1 kHz WAV masters (now referred to as pre-masters) are imported into the PQ editor and sequenced. The pause between tracks on the CD (or pregap) is definable but not normally used. Instead, spacing is added to the end of the previous track. Gapless playback (including crossfades) may be implemented.

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CD metadata, including CD-Text, UPC/EAN, and ISRCs, is defined in the PQ editor. A PQ sheet is generated at the end of the process. The PQ sheet is a track list containing CD markers for track start, pregap, and subindex, in addition to a listing of the total number of tracks and the total playing time of the CD. CD-Text, UPC/EAN, and ISRCs are usually included on the PQ sheet as well. All information on the PQ sheet is checked for accuracy prior to the CD pre-master being approved.

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CD PRE-MASTER FORMAT

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The preferred CD pre-master format for CD replicators and duplicators is a DDP pre-master. However, some CD duplicators do not accept DDP and, therefore, require a PMCD. The delivery master is termed a pre-master, since the actual production master for CD replication is the glass master created at the factory from the DDP pre-master.

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DDP

DDP (Disc Description Protocol) is a proprietary format developed by Doug Carson and Associates (DCA, Inc.) for specifying the content of optical discs, including CDs and DVDs. DDP is commonly used for delivery of a CD pre-master to a CD replicator or duplicator. A DDP pre-master consists of a ZIP file containing a folder with the DDP file set. The DDP file set created at Mindtree includes the following files:

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DDPID: Contains information about the format of the DDP pre-master.

DDPMS: Contains information about the files of the DDP pre-master.

PQDESCR: Contains subcode information about the tracks, UPC/EAN, and ISRCs.

IMAGE.DAT: Contains the audio data.

CDTEXT.BIN: Contains CD-Text information.

MD5_CHECKSUM.MD5: A text file containing MD5 checksums used to confirm that the files in the DDP file set were not modified during file transfer.

PQ-Sheet.pdf: A PDF document containing the track list of the CD.

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The most common method of delivery is to upload a ZIP file containing a folder with the DDP file set directly to the CD replicator or duplicator. The current DDP version is DDP 2.0.

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PMCD (Optional)

Some CD duplicators require a PMCD (Pre-master CD) for delivery of a CD pre-master. The PMCD is created by a Plextor PX-760A CD writer on professional CD-R media. The audio content and subcode information are identical to that of the DDP pre-master.

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QC

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Error Test (PMCD)

Audio CDs may contain one or more of the following types of disc errors:

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C1: The lowest level bit error measured in errors per second. This is referred to as BLER (block error rate). All audio CDs contain C1 errors to some extent. The Red Book standard allows for a maximum of 220 per second, but most CD duplicators prefer that the PMCD has a maximum C1 error rate of below 50 per second. C1 errors are correctable by the CD player's error detection and correction scheme.

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C2: A CD read error associated with poor master burning and physical defects. Although correctable to some extent, CD duplicators prefer that the PMCD contain no C2 errors.

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CU: An uncorrectable error. All CD duplicators will reject a PMCD with CU errors.

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All PMCDs produced at Mindtree undergo an error test to determine the number of C1, C2, and CU errors present. Discs are rejected if the average C1 error rate is over 1 per second and/or the maximum error rate is over 20 per second. Discs are also rejected if there are any C2 or CU errors.

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Program Audition

All DDP pre-masters and PMCDs are auditioned in real-time before being approved as delivery masters.

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DELIVERY MASTERS

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WAV MASTERS/VINYL PRE-MASTERS

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After creation of the masters, an invoice will be issued. Once payment has been received, an email will be sent containing a Dropbox link for downloading a set of WAV masters (and vinyl pre-masters if applicable). A Dropbox account is not required.

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Secure File Download Instructions

1 Click on Dropbox link in supplied email.

2 Enter provided secure file download password in link password field and click Continue.

3 Click on Download button.

4 Select either Direct download or Save to my Dropbox (Dropbox account needed for this option) to transfer all folders and files. Direct download saves ZIP files in your device's default downloads folder. The ZIP files should be unzipped and the files in the extracted folders used for reference and submission to the digital distributor. Save to my Dropbox saves the folders and their contents to your Dropbox and downloads the folders to all of the computers linked to your account.

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WAV PRODUCTION MASTERS

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All mastering projects include the following WAV production masters:

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2496 WAV Masters

24-bit/96 kHz high resolution/high sample rate masters intended as production masters for high resolution/high sample rate digital distribution and streaming.

*24-bit/88.2 kHz masters are provided for projects originating at 88.2 kHz

*24-bit/96 kHz masters are provided for projects originating at DSD64

*24-bit/176.4 kHz masters are provided for projects originating at 176.4 kHz

*24-bit/192 kHz masters are provided for projects originating at DSD128

*24-bit/192 kHz masters are provided for projects originating at 192 kHz

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2444 WAV Masters

24-bit/44.1 kHz high resolution masters optimized for encoding to both lossy formats (MP3, AAC, etc.) and lossless formats (FLAC, ALAC, etc.). These files should be utilized as production masters for digital distribution and streaming provided 24-bit masters are accepted.

*24-bit/48 kHz masters are provided upon request for audio for film/video projects

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1644 WAV Masters

16-bit/44.1 kHz masters optimized for encoding to lossy formats (MP3, AAC, etc.) and as CD pre-masters. These files should be utilized as production masters for digital distribution and streaming when 16-bit masters are required.

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2496, 2444, or 1644 FLAC files are provided upon request.

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Vinyl projects include the following WAV pre-masters:

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2496 WAV Pre-masters

24-bit/96 kHz high resolution/high sample rate pre-masters optimized for the vinyl medium. Two WAV files (one for each side) and PQ sheet are provided.

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CD PRE-MASTER

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For CD projects, a separate email will be sent containing a Dropbox link for downloading a DDP pre-master. A Dropbox account is not required.

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Secure File Download Instructions

1 Click on Dropbox link in supplied email.

2 Enter provided secure file download password in link password field and click Continue.

3 Click on Download button.

4 Select either Direct download or Save to my Dropbox (Dropbox account needed for this option) to transfer the file. Direct download saves a ZIP file in your device's default downloads folder. Save to my Dropbox saves the ZIP file to your Dropbox and downloads the file to all of the computers linked to your account. The ZIP file (and not the extracted folder) should be used when submitting the DDP pre-master to the CD replicator or duplicator.

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All CD projects include a DDP pre-master. The DDP pre-master consists of a ZIP file containing a folder with the DDP file set.

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An optional PMCD/Reference CD set is available at an additional cost.

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DDP Player

All DDP pre-masters produced at Mindtree include the M2pre-master DDP Player (by HOFA). The DDP player app allows you to audition the CD pre-master in its native format, as well as verify any metadata such as CD-Text. Reference CDs can be created directly from the M2pre-master DDP Player interface using any standard CD/DVD writer. Software executables for both Windows and Mac operating systems are provided.

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App Launch Instructions

1 Unzip the downloaded DDP ZIP file. Be sure to save the DDP ZIP file for submission to the CD replicator or duplicator.

2 Open the extracted DDP folder.

3 Open the Player subfolder.

4 Run the executable for either Windows OS or Mac OS.

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DIGITAL DISTRIBUTION

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Most independent artists use the services of a digital distributor (also known as an aggregator) for distribution. Listed below are the recommended master formats accepted by some of the major digital distributors:

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CD Baby

16-bit/44.1 kHz WAV, AIFF, or FLAC files

 

DistroKid

16-bit/44.1 kHz or 24-bit/44.1 kHz - 96 kHz WAV, AIFF, or FLAC files

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Ditto Music

16-bit/44.1 kHz WAV files

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iMusician Digital

16-bit/44.1 kHz or 24-bit/44.1 kHz, 88.2 kHz, 96 kHz WAV files

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Octiive

16-bit/44.1 kHz WAV files

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Record Union

16-bit/44.1 kHz - 48 kHz or 24-bit/44.1 kHz - 48 kHz WAV or FLAC files

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ReverbNation

16-bit/44.1 kHz WAV files

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Tunecore

16-bit/44.1 kHz WAV files