Creating 7.1 Audio
Microsoft Corporation
February 2005
Applies to:
Microsoft® Windows Media® Encoder 9 Series
Microsoft® Windows Media® Player 9 Series
Summary: Create Windows Media-based audio or video files containing eight discrete audio channels. You can then play back the files on surround-sound speaker systems through sound cards that support 7.1 audio. (6 printed pages)
Contents
Introduction
Microsoft® Windows Media® Encoder 9 Series and the Microsoft Windows Media Audio 9 Professional codec enable you to create audio or video files formatted for eight-channel 7.1 audio. After creating the files, users can enjoy a true surround-sound experience by playing the files using Microsoft Windows Media Player 9 Series or later, through a sound card that supports 7.1 audio, and a speaker system that includes up to seven speakers and one sub-woofer.
You can also create multichannel Windows Media audio files with fewer than eight channels, such as 4.0 and 5.1 audio files. Often, the easiest way to do this is to set up the encoder to source directly from multiple discrete WAV files. For example, to create a 5.1 audio file, you can source from six mono audio files. The encoder can also source from a single WAVEFORMATEXTENSIBLE or multichannel AVI file. WAVEFORMATEXTENSIBLE formatting enables you to create a WAV file with more than two channels.
You can use any of these methods to create multichannel Windows Media audio files with six channels or less. However, because an encoder source is limited to a maximum of six files, to create a 7.1 audio file you must source from a WAVEFORMATEXTENSIBLE or multichannel AVI file.
This article describes two methods for creating eight-channel AVI and WAV files, and then shows how to encode the files into Windows Media-based audio or video files. The first method uses Windows Media Mono to Multichannel Wave Combiner 9 Series, a command-line tool that you can download from the Microsoft Download Center page (http://www.microsoft.com/downloads/details.aspx?FamilyId=72F6F2FA-0ABE-4A92-9DD0-FD35B966825C&displaylang=en). The second method uses the Nuendo professional audio production program from Steinberg.
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Using Windows Media Mono to Multichannel Wave Combiner 9 Series to Create a Multichannel AVI File
The Multichannel Wave Combiner is a command-line tool that you can use to interleave two, six, or eight mono WAV files into one multichannel audio-only AVI file.
Before using this tool, create individual mono WAV files for each channel of an eight-channel surround-sound mix. To make the files easier to work with, include speaker positioning information in the file names. For example, use the name Song_FL.wav for the file corresponding to the front-left speaker. All files must be in uncompressed PCM format, must have the same length, and must have the same sample rate and bit depth.
Note The output file is in the AVI format in order to enable you to create files that are larger than 4 GB, which is the limit for WAV files.
Download and install the tool from the Microsoft Download Center page (http://www.microsoft.com/downloads/details.aspx?FamilyId=72F6F2FA-0ABE-4A92-9DD0-FD35B966825C&displaylang=en).
To create a multichannel AVI file
- Open a command prompt, and change to the directory in which the Multichannel Wave Combiner (WavAviMux.exe) was installed. The default installation directory is %systemdrive%\Programs Files\Windows Media Components\Tools\WAVAVIMUX.
- To run WavAviMux.exe, type the following at the command line, and then press ENTER:
WavAviMux –o [Output file] –iwav 8 [Input files] –mask 1599
- Output file. Includes the path and name, ending with .avi.
- Input files. Includes the path and name of the eight WAV files. The order of the input files determines how the files will be mapped to speaker positions according to the mask. The mask is a number that specifies the speaker layout. The following list shows how the channels correspond to speaker layout by default.
| This input file order |
Maps to this speaker position |
| 1 |
Front left |
| 2 |
Front right |
| 3 |
Front center |
| 4 |
Low frequency |
| 5 |
Back left |
| 6 |
Back right |
| 7 |
Side left |
| 8 |
Side right |
The Multichannel Wave Combiner installation includes a WrapperReadme.txt file that describes how to use the command-line options to create different multichannel file types. For example, you can create a video file with an .avi file name extension that includes multiple audio channels.
To test the output file, you can play it with Windows Media Player 9 Series or later. If you do not have a 7.1 surround-sound system, you can check the file size to make sure it contains all eight channels; the file should be eight times the size of one input file.
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Using Steinberg Nuendo to Create a Multichannel WAV File
Steinberg Nuendo is a media-production system used primarily to record and mix multiple audio and Musical Instrument Digital Interface (MIDI) tracks. This section describes how to use Nuendo to mix down a multi-track session to a multichannel WAV file. You will need Nuendo (and know how to use it) and a compatible computer sound system that has eight inputs and eight outputs.
There are two steps to this process: first, set up a custom 7.1 audio session, and then mix the session down to a multichannel WAV file.
Setting up a Custom 7.1 Audio Session
You must set up a custom 7.1 audio session because the 7.1 sessions provided with Nuendo contain channel masks that do not correspond to masks for wave_format_extensible files. If you use one of the default Nuendo sessions, the channels will not map correctly to the surround-sound speakers.
- Open eight audio tracks.
- On the Devices menu, click Show panels, and then select the VST Outputs tab. Check that buses 1 through 8 (or 1 through 4 for stereo pairs) are active.
- In the Devices panel, click VST Master Setup.
- In the VST Master Setup dialog box, create a custom 7.1 audio setup as follows:
- In Presets, click 5.1 SMPTE/ITU.
- In Number of channels, type 8.
- For channels 7 and 8, type a name and label that corresponds to how you plan to author and render the content. For example, the channels can be used as front left of center and front right of center, or side left and side right. To add the channel name and label, double-click the text box.
- (Optional) For channels 7 and 8, change the speaker placement in the Azimuth column to correspond to how you plan to author and render the content.
- In the Devices panel, click VST mixer. At the bottom of each channel strip is an indication of the output/bus to which each channel is routed. Click this area; a menu appears that lists the 7.1 channel mask. Select the output that corresponds to the channel position.
- Click Store to save the session for future use.
Mixing Down the File
After you have recorded, imported, or created your audio content, mix the session down to a multichannel WAV file by doing the following:
- Start Nuendo.
- Highlight the eight tracks.
- On the File menu, click Export, and then click Audio Mixdown.
- In Channel, click 8 Chan. Interleaved.
- Type a name for the file you are creating.
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Encoding the Final Windows Media File
To encode a Windows Media file that supports 7.1 audio, do the following:
- In the New Sessions dialog box, click Custom Session to open the Properties panel.
- On the Sources tab, in Source from, click File.
- Enter the name of the multichannel WAV or AVI file.
- On the Output tab, clear the Push to server and Pull from encoder check boxes.
- Select the Encode to file check box.
- In File name, enter the output file name and path.
- On the Compression tab, in Destination, click Web server (progressive download) or Windows Media server (streaming).
- In Audio, click Multichannel audio (CBR).
- Click Edit.
- On the General tab of Custom Encoding Settings, in Media types, select the Audio checkbox, in Mode, click CBR, and in Codec, click Windows Media Audio 9 Professional.
- On the bit-rate tab, in Audio format, click one of the following 7.1 audio formats:
- 384 kbps, 48 kHz, 7.1 channel 24-bit CBR
- 768 kbps, 48 kHz, 7.1 channel 24-bit CBR
- 768 kbps, 96 kHz, 7.1 channel 24-bit CBR
- Click Apply, and then encode the file.
You can save the custom session and export the profile to make it easy to create more 7.1-channel Windows Media files.
The encoder uses the channel mask of the multichannel WAV or AVI file. If you want to change the channel mask, or create multiple encoded files with different masks, you can use the Microsoft Windows Media Audio 9 Professional Channel Mask Mapping Tool. For more information, see Using the Windows Media Channel Audio 9 Professional Channel Mask Mapping Tool (/windows/windowsmedia/howto/articles/audio9procmmt.aspx).
You can make sure your system is set up properly by downloading the 8-Channel test files from the Microsoft Download Web site. The download contains a multichannel WAV file and the encoded Windows Media file.
8 Channel test files
Download now! (http://download.microsoft.com/download/6/b/1/6b17045c-6ce8-4dc4-a3b5-2717b8711fc8/8Channel.exe).
(1378 KB – 9 min @ 28.8 kb)
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