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Digital distribution’s challenge to mastering

From embedding album credits to Mastered for iTunes, PSNEurope unravels the challenge to mastering posed by digital delivery of music.

Published in Geneva last August, the EBU document The Carriage of Identifiers in the Broadcast Wave Format sets out the standard that the UK’s Music Producers Guild hoped for: a consistent, organisation-to-organisation way of including a unique identifier within a BWF file.

Its central tenet is a definition of how the data stored in the Extensible Markup Language (XML) ‘chunk’ of the file should be expressed every time, to avoid confusion and to allow safe expansion of the amount of metadata carried with the audio.

The most important pieces of XML, from the point of view of mastering, are the International Standard Recording Codes (ISRC) that contain the credits necessary as the music flies around the digital ether. Broadcast usage, royalties, song identification, remastering security and several other key aspects of asset management should benefit from this breakthrough, although there are still issues concerning the precise location of audio data and metadata.
The MPG is currently in talks with the Producers & Engineers Wing of the Grammy Organization, with the main aim of ensuring that support for the initiative is backed by a clear understanding of how each file should be constructed.

Alchemy Mastering’s Barry Grint explains why. “The Grammy Organization received funding from the Library of Congress to look at the issue of metadata,” he points out, “and were heading down the path of putting all the metadata in the audio file. The problem with this approach is that, once the file has been bought, it’s impossible to update the information or to correct errors. So if the metadata is in the file you can’t update it. Furthermore, if all the possible metadata is included in the file, it adds to the file size. While this isn’t an issue when considered against a video file, it’s not an elegant answer if, say, 20% of the file size is data headers.”
The MPG would rather have the ISRC contain a link to the internet, says Grint. “If the information is held in a database online, it can be kept up to date because the ISRC will always be the reference. Some of the information, such as royalty breaks and so on, would be in an online database with access only to those eligible to view it. You would never want to put that in the public domain via a file header.”
Currently the Grammy Organization is working closely with digital supply chain consortium DDEX in an attempt to standardise credits and rights management, and broadly supports the inclusion of ISRCs in BWF files even if a universal recommendation is yet to emerge. It was also instrumental in another key development in digital delivery as it affects mastering, courtesy of IT-for-creatives giant Apple. MFiT For Purpose

Apple is flagging up its Mastered for iTunes campaign as a means of supplying “music as the artist and sound engineer intended”. As independent mastering consultant Crispin Murray pointed out in January’s PSNEurope, this raises as many questions as it answers. It’s now being suggested that Apple may provide a higher-resolution version that will use Fraunhofer’s HD-AAC codec, a lossless process admired by mastering engineers including those within the MPG Mastering Group.
At the end of February Grint, Ray Staff and Stevan Krakovic, representing the MPG Mastering Group, held a meeting with Apple – known to be a supporter of ISRC in BWF and a potentially powerful lobbyist in the US for its adoption. At the moment Apple is not commenting on the details of the strategy, but Staff reports that he’s working very closely with the corporation in order to move forward. “For me, it’s about finding the best working process to prepare files for MFiT,” he says, “and there are several issues around exactly how the Apple Mac receives and plays them. We’re also keeping Apple abreast of developments in the mastering world, such as the changes to the BWF specification that address ISRC. It has great potential for Apple and the music industry, if it’s adopted in the right way.” Pro-Codec V2

Within the manufacturing sector, there are signs of acceptance that digital distribution is here to stay. Version 2 of the award-winning Pro-Codec plug-in has now been released by Sonnox-Fraunhofer, building upon the original plug-in’s ability to audition, encode and decode audio with codecs such as MP3 and AAC in real-time. This version comes in the wake of MFiT, and adds Apple’s iTunes Plus codec for direct mixing and mastering for that application and said to monitor the same clip behaviour as the iTunes encoding chain.
“The Sonnox-Fraunhofer Pro-Codec was created as a collaboration between Sonnox and Fraunhofer IIS to address the needs of mastering engineers wanting to monitor audio in real-time through a variety of codecs,” comments Nathan Eames, sales & marketing manager at Sonnox. “It was met with great acclaim in 2011 by mastering engineers, broadcasters and even mix engineers, who all felt that the plug-in saved them significant time at the final stages of production in quality controlling their output. With the continuing adoption of Apple’s Mastered For iTunes programme in the mastering world, Sonnox and Fraunhofer felt it would be useful to include Apple’s AAC iTunes+ Codec in Version 2 of the Pro-Codec.
“Using Version 2 of Pro-Codec, the exact clipping behaviour of the iTunes encoding chain can be monitored and levels corrected if necessary. This has saved engineers a lot of time and trouble at the final mastering stages, and also given their clients confidence to know that what they’re hearing is exactly how it will sound when finally encoded by Apple for iTunes. Instead of mastering it well and then hoping for the best, it’s taken the guesswork out of what will happen when it gets sent to Apple.”
It should be remembered, of course, that at present Apple’s Mastered For iTunes programme is only available to Apple Mac users as, therefore, is the section of Pro-Codec Version 2 that caters for it. The extent to which Apple might want to promote its solutions in the PC-populated world of professional mastering is a question for corporation-watchers: market share does not always serve the same interests as consumer choice.
“Mastered For iTunes requires the down-sampling function within Core Audio,” points out Crispin Murray, now technical manager at Guilde Productions. “You supply 88.2kHz or 96kHz, and Core Audio reduces it to 44.1kHz and uses their latest algorithm to encode an AAC file. As I understand it, those algorithms are not public domain so, for non-Mac users, it’s not a real-time function: you have to render the whole thing out to a Mac and, if you wish, back again.”
You might well wish, because all of the established DAW platforms in professional mastering, from SADiE to Sequoia and Pyramix, are PC-based. The Sonnox-Fraunhofer Pro-Codec will allow auditioning of AAC – and of course MP3 – files in real time on these devices, but that’s not the same process as Mastering For iTunes. The algorithm is not the same. “Plus,” adds Murray, “the algorithm changes. It’s currently optimised for 256kbps release, so when that increases to 320kbps everything will need to be updated. Other changes to the codecs can come at any time.”
There are even those who advise that, for online delivery, it would be better to supply 44.1kHz audio for AAC encoding than 96kHz, or at least one of each to ensure meaningful library options further down the line. The future of consumer delivery, however, is far from in sync with the aims of mastering – and never has been, in the battle between quality and convenience.

“We went from vinyl to cassette, now from CD to iTunes…” says Murray, “but, even when we knew that excellent masters would be played on a Dansette, we tried to make the best records we could. That’s what we do: get it to sound the best it can on all releases.” Online Mastering Services

Most qualified studios now offer online mastering, including Abbey Road and the ‘iMastering’ service via Metropolis. Many more engineers have set up stall at home, offering similar services using upload and delivery methods such as YouSendit and DropBox. Most, however, warn against taking risks with inferior file types. Typical are these instructions from Topfloor Music’s Pete Maher, a veteran of countless chart-bound projects including U2’s last two albums and work ranging from The Killers to Katy Perry: “WAV and AIFF formats are recommended and will guarantee professional results. MP3s and WMA formats are highly compressed so not ideal for mastering.”
How has Apple’s iTunes initiative affected him? “I’ve only been asked to do it once so far,” he says, “by EMI for the Danish synth band Turboweekend, for an album produced by Danton Supple. They wanted ‘Mastered for iTunes’ quality and I was actually contacted by Apple directly. I was given the tools, I registered and it all worked fine, although I found it hard to differentiate between those results and a high-resolution MP3. On paper it’s better, but there’s not much in it. I think it would be a good idea if MFiT was promoted among the independents and the unsigned acts – it seems to be aimed only at the high-profile majors at the moment, and so far nobody from my regular clients from Polydor, Universal or Sony has expressed an interest.

“I also had to use a Mac, of course. I normally work on PC, and had to switch. It’s great if you live exclusively in a Mac world, but working on a PC I often come across problems – even just with the AIFF files, never mind anything else. I did hear, from Apple, that they were thinking of changing that and making MFiT available for everyone, PC or Mac, which would be great, but I don’t know when.”
This month, the MPG Mastering Group is inviting record companies, publishers, managers, artists and trade groups to attend an event drawing attention to these issues. “Anyone who earns a living from the performance of recorded music should attend,” says Barry Grint, and the reasons are clear. Fundamentally, music is slipping through the hands of the record industry – a development that online delivery only encourages. Recordings are in danger of being bundled in and out of facilities with inadequate reference to many of the gateway mechanisms previously in place, while the very ‘gateways’ themselves – from A&R departments to publishers – are often ill-equipped to swim with the tide of file formats coming at them. For details of the event check the MPG website.
Story: Phil Ward