Steinberg Media Technologies GmbH

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MP3 Surround

Since the release of Nuendo/Cubase 4, one can easily create a multichannel mix and directly export it into a MP3 surround file that can be played on freely available media players like Winamp, DIVX and the MP3 surround player.

The MP3 basics

The MP3 format (the official naming is MPEG-1 Layer 3) was developed by the Fraunhofer Institute for Integrated Circuits IIS and has been accepted as a part of MPEG-1 in 1992.

Basically, this format uses a lossy compression and reduction algorithm taking certain psycho acoustical effects like the masking of audio signals into account. Signals that are masked by other noticeably louder events can be removed to reduce the overall file size because they simply have no relevance for the audible signal. Depending on the compression rate, an uncompressed audio file can be downsized to a tenth (or even more) of its original size. Those smaller files can then be archived, send via email or downloaded much more easily.

The next generation: MP3 Surround

MP3 Surround addresses the increasing demand for multichannel applications and new surround file formats. Using advanced algorithms, a MP3 surround file achieves higher compression rates than other surround formats at the same quality while the resulting file is only about 10 percent bigger than a standard stereo MP3 file. In addition, the MP3 surround format is fully backwards compatible and can be used as a stereo file on any old non surround hard- and software players.


Fig.: Principle of Encoding


Fig.: Principle of Decoding

You can also easily judge your own production in a surround environment without having to use Dolby, MLP or dts and compatible players for actually listen to surround sound. Now, even if Cubase and Nuendo deliver all the software tools for mixing in surround, there are some other requirements to be met - especially on the hardware side:

First, the audio interface has to offer six discrete audio outputs to be able to mix in surround and also to be able to export a 5.1 MP3 surround file using the mixdown feature. Usually, one sets up channels as left, right, center, LFE (Low Frequency Effects), left surround and right surround - comparable to Dolby Digital and dts. Then, six monitor speakers are needed to actually monitor the mix and the resulting file in surround sound. Even though a reference and perfectly set up listening environment might be hard to build, one should nevertheless try to get as close to the example on the left which shows an optimal speaker setup according to the EBU (European Broadcasting Union) as possible. At least try to find a way to keep the setup as symmetrical as possible to avoid different delays for each speaker/channel.

Working with Nuendo and Cubase

Now that all requirements are met, you have to create a multichannel 5.1 output bus in Nuendo or Cubase that can be used for mixing down all channels into a MP3 surround file. The VST connections in the Device menu allow you to do just that:

After the mix has been completed, the result can be rendered into a MP3 surround file using the audio mixdown in the File -> Export menu. Please choose "MPEG 1 Layer 3" as the file format, select the 5.1 output as the audio engine output and select the bit rate of your choice. We recommend starting with 192 kBit/s for a good and balanced export result.
Just remember: the lower the bit rate, the smaller the MP3 file but the more limited the audio quality because of the reduction.

Export dialog in Cubase 7

Now, the audio mixdown creates a MP3 surround file that can be used in any player (at least in stereo) and that can also be re-imported in Nuendo/Cubase 4. Both detect a six channel audio file and all channels can be imported onto discrete audio tracks for further editing again. For details on how to mix in surround, monitor in surround (using the control room) and the export process, it is recommended to consult the manual.

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