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SESSION NOTES 10 “Streaming Audio” (part 2 formats and stuff)


Hi folks, carrying on from last month i want to look at formats and related topics for streaming audio. Unfortunately for studio owners, audio engineers and musicians music making is an expensive business. That ‘gear’ you see in the studio costs a LOT of money. In the studio we strive to bring you the absolute finest quality audio using very expensive equipment. I know engineers (myself included) that will spend upwards of £5000 for a single piece of ‘gear’, be it a microphone or a fancy valve analogue equaliser to realise your musical dreams to the highest technical quality. The end result for the consumer will often be (these days) a digital stream of substandard audio usually played back on a telephone!!


To me the sound of streamed audio is the equivalent of a thumbnail picture. There’s a glorious full bandwidth version on the originators platform somewhere but the consumer gets the thumbnail … and then pays for it!!!! There are many companies who have authored file formats that claim to provide high quality audio but in reality simply provide “audio vomit”. Here then are the most popular formats available. Downloads are different in that you can obtain full resolution audio that is downloaded. Casual listening is always streamed.


Last month I mentioned OGG VORBIS. well, here it is. Ogg Vorbis actually describes two things. Ogg is a free open container format. A container (or wrapper) is a metafile format which describes how data and metadata coexist in a computer file. Vorbis is a free ‘open source’ software project that produces an audio coding format and a reference CODEC (encoder-decoder). The compression is ‘Lossy’ which means data from the original file will be lost in order to produce smaller files. It was started in 1993 by Chris Montgomery while at MIT. The Xiph. Org Foundation maintains Vorbis and Ogg (the container). The format is known as OGG VORBIS. Incidentally, the name ‘Vorbis’ comes from a Terry Pratchett book called “Small Gods”. The character therein is named “Exquisitor Vorbis”. I recorded the audio book version with Nigel Planer for ISIS publishing back in the 90’s. Well, there’s a thing.


This file format was developed in response to the Fraunhofer-Gesellschaft Institute’s cute little invention … the MP3. MP3 (MPEG-1 or (2) Audio layer III) gets its name from the Moving Picture Experts Group. Like Vorbis it data compresses the audio using psychoacoustic modelling techniques. MP3 uses … wait for it … ‘Modified Discrete Cosine Transforms’ to economically pack the data into the tiniest size available. It manages to cram full bandwidth audio signals into approximately 9% of the original size. The science tells us that we shouldn’t be able to detect any meaningful difference. Our ears unfortunately tell us otherwise. Is there really any musician or sound engineer out there that can’t tell the difference … i truly doubt it.


Really sorry about this but MPEG-4 (part III) audio uses a compression technique known as “TwinVQ’ … ‘transform-domain weighted interleave vector quantisation’. It is used for ultra low bitrates around 8Kbit/s. Not too great for audio. I do apologise for the tech stuff here, I wanted to keep things light for the layperson or those of casual interest but fuck it I went and got technical again … sorry.


Next up is the FLAC format. It stands for ‘Free Lossless Audio Codec’. Now lossless is immediately appealing to audiophiles like my self or even yourself. It works on a principle not too dissimilar to a ZIP file which i’m sure you all know and use. It encodes the audio data and then decodes it back to the original full bandwidth sound (we know and love). It was developed in 2000 by those pre-mentioned Xiph. Org Foundation people and therefore has a family link with Ogg Vorbis. It (unlike MP3) is a free open source algorithm. It has support for tagging and album art. I had to pay for my MP3 software in the mid 1990’s in order to offer this new format to my clients when floppy disks were the removable storage option, (2Mb) whoopee.


As technology develops I’m sure audio quality in the streaming world will improve greatly in the future. It HAS to. The £9000 that a Neumann U47 microphone costs sounds like a £9 microphone when spewed out of Spotify!!


Next month-: I will begin to unravel the mysteries of what people call the “dark art” … Mastering.

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