Knowledge Bank

news category created 23 August 2009 written by Mick Glossop

Optimising Your Mix

Optimizing Your Mix Part 2, second in a series of events organised by the Music Producers Guild to help producers get the most out of their mix/master, took place in August 2009 at Dean Street Studios in London’s Soho.

 

On the panel were Bill Foster, of Digital Decoded; Virgilio Bacigalupo, of the Fraunhofer Institut für Integrierte Schaltungen, Germany (the inventors of MP3)) and Air Mastering’s Matt Colton. It was moderated by Phil Harding.

 

With its comfortable sofas, chairs and bean bags, Dean Street Studio’s live room gave the event an informal and relaxed atmosphere. Everyone had the opportunity to take part in the very heated debates, which made the event feel more like a discussion workshop. Among those in the audience were mastering engineers from a number of facilities, including Ray Staff who was on the panel in the first event in the series.

 

After an introduction by Phil Harding, Bill Foster gave an overview of compressed audio formats, their evolution over the years and explained that we are still living with a dial-up internet legacy. This dictated the 128kbit/s MP3 standard that we sadly still have today, even though it does not sound very good and modern broadband speeds would allow for much higher bit rates. Apparently MP3 was initially only meant for telecommunications and as a emergency replacement for broadcasting. It was not really designed for music use!

 

After presenting the history of Digital Richats Management (DRM) and its issues and uses in different online stores and formats, Bill explained the difference between lossy and lossless codecs and who uses them and where.

 

This led on to Virgilios presentation, who gave a basic overview of how lossy audio codecs like MP3 work and what the psychoacoustical mechanisms and assumption are. Within his powerpoint presentation he also played some audio examples to demonstrate the effects of frequency masking/adjacent band masking and in-band masking, which are at the heart of the perceptual models that define MP3/AAC encoders.

 

He also pointed out how different perceptual models (as by different manufacturers of MP3 encoders) result in very different sounding MP3s, because only the bitstream is standardised, not the encoding. So just as every AD/DA convertor will sound different, and might be more or less appropriate for a specific audio source, the same is true for MP3 encoders, mainly because of their underlying perceptual model and the spreading of the encoding bands etc.

 

Virgilio also gave a presentation for a new technology Fraunhofer is developing called AAC-HD. This new scalable audio file format, which has a lossy AAC core similar to those sold on itunes, also has an enhancement layer, including all the information the AAC encoder throws away. This means it can losslessly resolve up to 24bit/192kHz as well as all the metadata like ID3 tags, cover art, lyrics etc. Because it is completely scalable, anyone with enough bandwidth/hard drive space will have up to a 24bit/192kHz file – the same as you get from your DAW/mastering. If less bandwith/space is available it can automatically and gradually scale down to 96k/48/44.1 etc, right down to 128kbit/s lossy AAC. It is also 100% compatible with existing players, so you could have the full quality version in itunes, but only the lossy AAC in your ipod (with reduced file size!).  You could also have the full file on your ipod/etc, but since it only does AAC, you would only hear AAC. However, if you plug into a docking station you could stream the full quality 24/192 to that.

 

Before you all try rushing out to buy this new technology it is worth pointing out that Fraunhofer don’t actually make and sell products – they only develop technologies that other people can license.

 

After quickly introducing MPEG surround, which is a scalable, lossy surround format with the facility for inbuilt stereo foldback streams, Virgilio presented the topic that resulted in the hottest debate of the evening. This is a plug-in, through which you can listen to the effect that the MP3 encoder/decoder is having on your audio in realtime, with a setting for different sample rates.

 

Virgilio suggested they were developing this plug-in for Pro Tools only, which initiated an outcry amongst the mastering engineers in the room who were all very interested in such a plug-in and have been waiting some time for someone to develop it. They argued that it would be most valuable to mastering engineers rather than mixers and that because most mastering engineers use PC based programs such as SADIE rather than pro Tools, a better platform would be something like VST.

 

Matt Colton finally gave the mastering engineers perspective on MP3. His main points were that mastering engineers sadly never get to encode the MP3s/AACs because the CDs they mastered were sent straight to batch ripping plants that don’t care about quality.

 

Bill Foster compared this to the early days of CD where similar things happened with CD manufacturing. In those days unattended transfers to digital were made, with badly adjusted levels for the AD convertors, resulting in bad quality CDs.

 

Matt stated that after many experiments he had come to the conclusion that there was not much you could do to your mix to ensure a better sounding MP3. All you can do is make sure you encode from the highest quality source (ideally 24/192), don’t peak at 0dbfs (as this can create overs in encoding), and be aware that different codecs can sound very different. He also complained that not being able to monitor what a codec does in real time makes it guesswork. That situation would obviously be rectified by a plug-in such as the one proposed above.

 

Summing up the event, Mick Glossop said that the title “Optimizing Your Mix” was perhaps misleading as there is not much you can do to optimize your mix for MP3 other than to do the best mix possible, which you would want to do in the first place!

 

Nevertheless, the heated discussions that took place and the exciting new technologies that were introduced made the event interesting and exciting for both panel and audience. Virgilio has now asked the MPG to help develop the plug-in by giving our feedback on this proposed new technology.

 

The third event in this series is now at the planning stage and may well include a discussion on the future of online sales. We will let you know when details of content, date and venue have been agreed.

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