Copyright: (c) 1996 Progressive Networks, Inc.


 Contents

The following Help Topics are available:

Overview

Encoding Files

Setting Encoder Options

Bandwidth Negotiation

Changing the Description of RealAudio Files

Troubleshooting

For the latest information on RealAudio products and Web sites, visit the Progressive Networks home page at:

http://www.realaudio.com

The latest support and technical information is available at:

http://www.realaudio.com/help/

For Help on Help, Press F1


 Overview

RealAudio Encoder enables you to compress audio files or input from a sound device into one or more RealAudio formats. Output can be sent to a file or directly to RealAudio Server for live broadcasting. You can select input files by browsing from within the Encoder, or drag and drop files onto the Encoder icon for automated processing. The Encoder window displays information about input and output file formats and has fields for entering descriptive information.

RealAudio content may be created either from previously recorded digital audio files, or from an external audio source.  Prerecorded files may be in .au, .wav and raw .pcm audio formats.  External audio may be fed from a recorded source, such as DAT (Digital Audio Tape), CD (Compact Disc), or directly from a mixing console or microphone.  Prior to encoding, prerecorded audio should be preprocessed using one of the various sound editing utilities available to maximize the audio quality of the encoded content.  Similarly, when encoding live source audio, the input levels should be prepared and tested as before any professional recording session.

Encoding Files

Drag-and-Drop Encoding

Setting Encoder Options

Changing the Description of RealAudio Files

Bandwidth Negotiation

Batch Encoding

Troubleshooting


 Encoding Files

The RealAudio Encoder allows you to create a .ra file from both pre-existing audio files and live sources.  The RealAudio Encoder provided with the RealAudio Server has the added ability to provide audio directly for broadcast over your private network or over the Internet. To convert a digital audio file to RealAudio format, the file must be one of the Supported File Types and File Extension

As part of the Encoding Process, you can specify options such as the compression type and the copyright string to be included in the file. See Setting Encoder Options for more details concerning additional Encoder features.

On a typical Pentium PC, the time required to encode a file is currently approximately 80% of the file's duration.  For example, a one-minute file will encode in approximately 50 seconds on a Pentium PC.  Actual performance will depend on your configuration.

Encoding a Static File

Encoding Live Output

Drag-and-Drop Encoding

Live output is only available on the RealAudio Encoder provided with the RealAudio Server.


 Supported File Types and File Extension

The RealAudio Encoder converts .WAV, .AU, and .PCM files into the RealAudio format.  The original source files may be recorded at a variety of sampling rates.

To generate RealAudio files, start with a file in one of the following formats:

.WAV: 8 kHz, 11 kHz, 22 kHz, 44 kHz in either 8- or 16-bit format, monophonic

.AU: 8 kHz, 22 kHz, 44 kHz, monophonic

.PCM: 8 kHz, 11 kHz, 22 kHz, 44 kHz in either 8- or 16-bit format, monophonic

Please note that the Encoder does not support compressed variants of the formats described above. If you encounter problems encoding a file, verify that it is neither stereophonic nor compressed before proceeding with more extensive Troubleshooting

If your audio is in a format not supported by the RealAudio Encoder, you can convert it using a variety of sound editing tools available for the Windows platform to convert the file to a supported format.

To hear examples of RealAudio content produced by other RealAudio users, see Timecast: The RealAudio Guide at:

http://www.timecast.com


 Choosing an Encoding Algorithm

When you encode an audio file, you select an encoding algorithm. The RealAudio Encoder can encode using several different algorithms. Each encoding algorithm is optimized for a particular type of audio and connection speed bandwidth. You need to select one or more algorithms that best suit your needs.

It is possible to offer more than one encoding algorithm from your RealAudio Server. In this way, you can reach the widest possible audience while still providing high-bandwidth users with the best listening experience. Using Bandwidth Negotiation, you can configure your site to automatically serve the appropriately encoded file.

For more information about Bandwidth Negotiation, refer to Bandwidth Negotiation

The following table lists the available algorithms, a description of each algorithm, the frequency response, and the file size per second of audio.

Encoding Algorithm	Description	File Size per Second
RealAudio 2.0 - 14.4	Use for speech over 14.4 Kbps modems. Frequency response: 4.0 kHz	1 KB
RealAudio 2.0 - 28.8	Use for voice content and voice with background music over 28.8 Kbps modems. This option increases intelligibility under high packet loss conditions. Frequency Response: 4.0 kHz	1.8 KB
RealAudio 3.0 - 28.8 Mono, full response	This option gives the brightest sound for delivery over 28.8 modems.  If audio artifacts occur, encode with the medium response option.  Frequency response: 5.5 kHz	2 KB
RealAudio 3.0 - 28.8 Mono, medium response	This option may improve clarity for music with snare drums, cymbals and vocals.  If audio artifacts occur, encode with the narrow response option.  Frequency response: 4.7 kHz	2 KB
RealAudio 3.0 - 28.8 Mono, narrow response	This option may improve clarity for speech-intensive music or noisy signals.  Frequency response is somewhat reduced.  Frequency response: 4.0 kHz	2 KB
RealAudio 3.0 - 28.8 Stereo	Use for general stereo content.  Frequency response: 4.0 kHz	2.5 KB
RealAudio 3.0 - ISDN Mono	Use for general mono content over IDSN connections.  Frequency response: 11.0 kHz	4.9 KB
RealAudio 3.0 - ISDN Stereo	Use for stereo content over ISDN connections.  Frequency response: 8.0 kHz	4.9 KB
RealAudio 3.0 - Dual ISDN Mono	Use for optimal quality for mono content.  Frequency response: 20.0 kHz (CD Quality)	9.8 KB
RealAudio 3.0 - Dual ISDN Stereo	Use for optimal quality for stereo.  Frequency response: 16.0 kHz (Broadcast Quality)	9.8 KB


 Encoding a Static File

There are two versions of Encoder for Windows: a free Encoder available for download from Progressive Networks web site and a Live Encoder that is included when you purchase RealAudio Server. You can encode a static file using either Encoder.

Note	The RealAudio Encoder included with RealAudio Server can deliver live content for broadcasting live events.

To encode a file using RealAudio Encoder for Windows:

1.	In the Source pane, select the File tab to encode from a static file or select the Live Stream tab to encode from a live source. If you select the Live Stream tab, continue with Step 4.

Note	The free RealAudio Encoder cannot broadcast a live event. If you have the RealAudio Live Encoder and want to broadcast a live event, refer to Encoding Live Output

2.	In the File tab, enter the directory and filename of the previously digitized audio file or click Browse to find the file. RealAudio Encoder automatically detects the sampling rate, format and resolution of a source file and display them in the Format box. If the Encoder cannot recognize these attributes, a dialog box appears where you can specify the information.

When you have selected the file to encode, a graphical representation of the file appears below the Source pane and the length of the clip is displayed. You can choose to not display the Audio Signal by clearing Display Audio Signal from the Options menu.

3.	In the Description pane, enter the Title, Author, and Copyright information for your RealAudio output. These fields are optional.

4.	If you want to allow RealAudio Player Plus users to save your RealAudio signal to disk, select Enable Selective Record.

5.	If you want to allow RealAudio Player Plus users with 14.4 Kbps modems to experience RealAudio files encoded for a higher bandwidth by partially downloading audio data before beginning playback, select Enable PerfectPlay.

6.	In the Destination pane, select File to encode a static file. If you have the RealAudio Live Encoder, and want to serve the file as you encode, select the RealAudio Server tab. (This option is not available in the free RealAudio Encoder.)

Note	For information about encoding live audio and the RealAudio Server tab, refer to refer to Encoding Live Output

7.	In the fields on the File tab, enter the name and location of the .ra output file. The Encoder suggests a default output file with the same name (but with a .ra filename extension) and in the same directory as the source file. You can modify the output filename.

8.	In the Compression pane, select the appropriate compression type.

For a description of each encoding algorithms, refer to Choosing an Encoding Algorithm.

9.	If you want to listen to your audio as it is being encoded, select Play While Encoding from the Options Menu. Using this feature, however, may slow the encoding process.

10.	If you select Play While Encoding, you can choose to listen either to the input file or to the decompressed .ra output file. Select one of these options from the Options menu.

11.	Click [image], or the Start Encoding button to start the encoding process.

You may choose to view the progress indicator which shows the percentage completed or to view side-by-side plots of the input and output waveforms by clicking Show Audio Signal on the Options menu. Showing the waveforms may slow down the encoding process.

Note	You can change Encoder default settings on the Preferences window. For more information, refer to Setting Encoder Options

12.	Listen to the newly encoded file with a RealAudio Player.

Note	To stop encoding the file, refer to Stop Encoding


 Encoding Live Output

The RealAudio Encoder included with RealAudio Server can deliver live content for broadcasting live events. The free RealAudio Encoder available from the Progressive Networks Web site does not support live delivery.

Note	Previous releases of RealAudio Encoder and RealAudio Server used the Live Transfer Agent (LTA) to deliver live content; the LTA is no longer used.

To deliver live content, you need:

•	A live audio source

•	A computer running a RealAudio Encoder

•	A server running a RealAudio Server

RealAudio Encoder and RealAudio Server computers can be on different platforms.

To deliver live content using bandwidth negotiation, use one computer for each bandwidth. Each computer runs a Live Encoder connected to one RealAudio Server. For more information on bandwidth negotiation, refer to Bandwidth Negotiation

To encode and broadcast live content:

1.	Click the Live Stream tab in the Source frame.

2.	In the Description pane, enter the Title, Author, and Copyright information for your RealAudio output. These fields are optional.

3.	If you want to allow RealAudio Player Plus uses to save your RealAudio signal to disk, select Enable Selective Record.

Note	Enable PerfectPlay is not available for live broadcasts.

4.	In the Destination pane, click the RealAudio Server tab.

5.	In the Host box, type the domain name or the IP address of the RealAudio Server computer.

6.	In the Port box, type the port number from the PnaPort configuration setting in the RealAudio Server configuration file.

7.	In the File Name box, type a name for the live clip being encoded. This is the filename part of the URL that goes in the metafile (.ram) used to access the live broadcast.

8.	In the Password box, type the password from the Encoder Password configuration setting in the RealAudio Server configuration file.

9.	In the Compression pane, select the appropriate compression type.

Note	You can change Encoder default settings on the Preferences window. For more information about the Preferences window, refer to Setting Encoder Options

10.	Click [image], or the Start Encoding button to begin encoding the input and sending the data to the specified RealAudio Server.

Note	To stop encoding the file, refer to Stop Encoding


 Drag-and-Drop Encoding

RealAudio Encoder supports two types of drag-and-drop encoding:

•	Clicking an input-audio-file icon and dragging it onto an open Encoder window enters path and filename information into the appropriate Encoder fields. Then, you need only enter the descriptive information and settings and click [image] to begin the encoding process.

•	You can also drag and drop an input-file icon onto the RealAudio Encoder icon. The file will be encoded using the default output file name and the most-recently saved Description and Options. Be sure that you have saved the settings (by selecting Save Default Settings from the Options menu) that you want applied.


 Stop Encoding

•	Select Stop Encoding from the Encode menu or click on the corresponding toolbar button.


 Setting Encoder Options

Turning the Audio Signal Display On or Off

Enable Selective Record

Enable Perfect Play

Play While Encoding


 Turning the Audio Signal Display On or Off

The RealAudio Encoder displays the audio signal for both the input and output files.  Turning off this feature results in somewhat faster Encoding.

To change the setting of this option:

•	Toggle Show Audio Signal from the Options menu.


 Enable Selective Record

Selective Record enables the RealAudio Player Plus to record a copy of a RealAudio file to disk.

To enable Selective Record:

•	Check this option to allow the Player Plus to save a copy of this file.  Clear this option to prevent the Player Plus from saving a copy of this file.


 Enable Perfect Play

Perfect Play enables the RealAudio Player Plus to improve audio quality by increasing the amount of audio data buffered before playing.

To enable Perfect Play:

•	Check this option to allow the Player Plus to use PerfectPlay for this file.  Clear this option to prevent the Player Plus from using PerfectPlay for this file.


 Play While Encoding

You can listen to the audio as it is encoded if your PC has sufficient performance.

Note	To help ensure real-time performance, this option is not available for live input streams.

To play while encoding:

•	Click Play While Encoding in the Options panel.

Note	If the audio skips or is not available, your computer may not have sufficient performance to play correctly.


 Storing Default Options

To save the current options as the default settings to be loaded each time you start the Encoder:

•	Click Save As Defaults from the Options menu.  The settings stored include the default Compression Type and the description fields.


 Changing the Description of RealAudio Files

You can change the Title, Author, or Copyright text, and modify the Selective Record and PerfectPlay settings in a .ra file using several different methods:

Method	Description
RealAudio Encoder	Open a .ra file, edit the text fields, and click Encode. RealAudio Encoder modifies the fields. The RealAudio Encoder does not re-encode the file, it just modifies the text strings.  Refer to Encoding Files
RealAudio Exchange Tool (rax)	This is a command line tool available for Windows and Unix.  Refer to RealAudio Exchange Tool
.ram File	Set the Title, Author, and Copyright text strings in the .ram file. Refer to Error! Reference source not found. in the Content Creation Guide, available from the RealAudio Web site.
Events Compiler or Timeline Editor	Set the Title, Author, and Copyright text strings in the .rae file using either of these tools. Refer to on-line help in the Timeline Editor.


 RealAudio Exchange Tool

You can change the title, author, or copyright text, and modify the Selective Record and PerfectPlay settings in a .ra file by using the RealAudio Exchange (rax) tool. The rax tool is run from the command-line by typing:

rax [options] file

where the following options are available:

Feature	Description
-o	Use this option to specify the output RealAudio file name. If you do not use this option, then the input file is overwritten by the updated file.
-t	Use this option to specify a Title string.
-a	Use this option to specify an Author string.
-c	Use this option to specify a Copyright string.
-w	Use this option to enable or disable Selective Record. Valid option are:  0 Disabled  1 Enabled
-p	Use this option to enable or disable PerfectPlay. Valid option are:  0  Disabled 1 Enabled
-f	Use this option to fix a corrupted RealAudio file header.
-I	Use this option to display the .ra file header information.
-ir	Use this option to display header information for multiple files in a directory.
-help	Use this option to print the options list to the screen.
-v	Use this option to display the version number of your RealAudio Exchange tool.
Changing Title, Author, or Copyright Text

Copying a File to New File

Changing Header Information


 Changing Title, Author, or Copyright Text

Using the rax tool you can change the Title, Author, or Copyright text strings. The following examples show how to change the Title text.

To change the title text in a .ra file:

•	Use the -t option by typing the command:

rax -t"My New Title"  file.ra

To change the title of several .ra files:

•	Use the -t option by typing the command:

rax -t"My New Title"  *.ra.

This command changes the title string in all files that match the wildcard "*.ra".


 Copying a File to New File

If you want to create a new file and not overwrite the existing .ra file:

•	Use the -o option by typing the command:

rax -t"My New Title"  -ofile_new_title.ra file.ra


 Changing Header Information

Using the rax tool you can change the header information of the .ra file.

To display .ra file header information:

•	Use the -i option by typing the command:

rax -i file.ra

To display .ra file header information for multiple files contained in a directory:

•	Use the -ir option by typing the command:

rax -ir rafile_dir


Batch Encoding
 Running the Encoder from the Command Line

To automate the encoding of multiple audio files, you can specify command-line arguments that direct the Encoder to process an input file and then shut down.  The syntax is:

ENCODER  <file to encode>  [<settings file>]

where:

<file to encode>	is the digital audio file to encode

<settings file>	is the name of a settings file.  This parameter is optional.

Note: If you place the files you want to encode and their corresponding settings files in the same directory as the RealAudio Encoder, you will not have to qualify any paths.  However, if you would like to encode files in other directories, you need to specify the complete paths to all input files.  You also need to have the RealAudio encoder in your path.

Settings File Format


 Bandwidth Negotiation

Bandwidth negotiation requires only one link on your Web site to a particular clip. To provide content in multiple formats without bandwidth negotiation, your Web site must have a separate hypertext link and metafile for each format.

Bandwidth Negotiation Explained

Bandwidth Negotiation Example

Using the Bandwidth Negotiation Utility


 Bandwidth Negotiation Explained

File organization is the key to bandwidth negotiation. A single link on a Web page, which references a directory with three RealAudio files encoded using different algorithms. The following steps explain how the RealAudio Player and RealAudio Server determine which file to play based on bandwidth.

1.	The user clicks a link to a RealAudio metafile on a Web page.

2.	The Web server returns the metafile to the Web browser and based on the .ram file extension, sets the MIME type of the metafile to audio/x-pn-realaudio.

3.	The Web browser looks up the MIME type of the metafile, starts RealAudio Player as a helper application, and passes it the metafile.

4.	RealAudio Player reads the first URL from the metafile and requests it from RealAudio Server. Based on its preference settings, RealAudio Player also sends a list of RealAudio compression types it supports.

5.	RealAudio Server checks the directory specified by the URL and begins streaming the highest bandwidth file supported by RealAudio Player.

The name of the RealAudio file specified in the URL in the metafile is actually a directory on the RealAudio Server computer with the .ra filename extension. Within that directory are the individual files for each format. Name the files based on the following table, which is sorted in order of increasing bandwidth:

Encoding Algorithm	Filename
RealAudio 2.0 - 14.4	14_4.18
RealAudio 3.0 - 28.8 Mono, full response RealAudio 3.0 - 28.8 Mono, medium response RealAudio 3.0 - 28.8 Mono, narrow response	dnet.20
RealAudio 3.0 - 28.8 Stereo	dnet.25
RealAudio 3.0 - 28.8	28_8.36
RealAudio 3.0 - ISDN Mono RealAudio 3.0 - ISDN Stereo	dnet.50
RealAudio 3.0 - Dual ISDN Mono RealAudio 3.0 - Dual ISDN Stereo	dnet.100
Note that several encoding algorithms have the same filename. That means that you can deliver only one of those formats for any given URL.

The following table shows the file formats that each version of RealAudio Player requests and in what order they are requested:

Player Version	Bandwidth Setting	Files Requested
1.0	All	14_4.18
2.0	14.4	14_4.18
2.0	28.8, ISDN, T1	28_8.36 14_4.18
2.1	14.4	14_4.18
2.1	28.8, ISDN, T1	28_8.36 14_4.18
3.0	14.4	14_4.18
3.0	28.8	28_8.36 dnet.25 dnet.20 14_4.18
3.0	ISDN	dnet.50 28_8.36 dnet.25 dnet.20 14_4.18
3.0	T1	dnet.100 dnet.50 28_8.36 dnet.25 dnet.20 14_4.18
Note	RealAudio Player 3.0 and later with a 28.8 Kbps connection always plays the RealAudio 28.8 (28_8.36) format if it is available. If you want to provide another 28.8 format such as 28.8 Stereo (dnet.25), do not also provide the 28_8.36 format. If you do not provide any format supported by a Player, that Player receives a message to upgrade to the current Player release.

Bandwidth Negotiation Example

Using the Bandwidth Negotiation Utility


 Bandwidth Negotiation Example

In this example, you deliver one of three RealAudio formats depending on the connection speed and RealAudio Player version.

To setup this example:

1.	Encode the source file in the following formats:

•	RealAudio 2.0 - 14.4

•	RealAudio 3.0 - 28.8 Stereo

•	RealAudio 3.0 - ISDN Stereo

2.	Create a metafile named mozart.ram containing a URL such as:

pnm://audio.realaudio.com/music/mozart34.ra

3.	Create a link to the metafile in a Web page. The following HTML code is a typical link:

<A HREF="http://www.realaudio.com/cl/mozart.ram">
Listen to Mozart</A>

4.	On the RealAudio Server computer, create a directory named mozart34.ra in the /music directory.

5.	In this directory, store the three RealAudio files, renamed 14_4.18, dnet.25, and dnet.50 as shown in the previous table. You can do this manually, use the raconv utility described in the next section, or write your own automation script.

The file that is played depends on the Player connection and version:

•	ISDN or faster connection with RealAudio Player 3.0 or later: RealAudio 3.0 -ISDN Stereo format (dnet.50)

•	28.8 Kbps connection with RealAudio Player 3.0 or later: RealAudio 3.0 -28.8 Stereo format (dnet.25)

•	14.4 Kbps connection with RealAudio Player 3.0 or later: RealAudio 2.0 -14.4 format (14_4.18)

•	14.4 Kbps or faster connection with RealAudio Player version 2.1 and earlier: RealAudio 2.0 -14.4 format (14_4.18)

Note 1	If you do not supply a RealAudio 2.0 -14.4 or RealAudio 2.0 -28.8 format file, users with RealAudio Player 2.1 or earlier receive an error message that they need to upgrade their Player.

Note 2	If you supply a RealAudio 2.0 -28.8 format file (28_8.36), RealAudio Player 3.0 or later with a 28.8 Kbps connection always plays the 28.8 format file; the 28.8 Stereo format file is never played.

Bandwidth Negotiation Explained

Using the Bandwidth Negotiation Utility


 Using the Bandwidth Negotiation Utility

raconv utility helps you arrange your files into the organization required for bandwidth negotiation by generating the directory with the .ra extension and placing the appropriately renamed files in that directory. The utility uses information in the RealAudio file to determine how to rename the file. Because the utility renames files, keep a back up of your original files until you are sure that the process was successful.

Note	The raconv utility does not convert between RealAudio formats. Use RealAudio Encoder to create a file with each needed format.

To organize your files for bandwidth negotiation:

1.	Encode your RealAudio files in the formats you want to support.

2.	Store your recorded files in separate directories, one for each final format name. For example, RealAudio 3.0 - 28.8 Mono, narrow response and RealAudio 3.0 - 28.8 Mono, medium response go in the same directory, because they are both renamed dnet.20. The files that contain the same audio source encoded in different formats must have the same name. For example, if the URL specifies mozart34.ra, you need file named mozart34.ra in each directory.

3.	Type the command:

raconv <InputFileName> <ContentDirectory>

Where InputFileName is the file to be turned into a directory and underlying RealAudio file and ContentDirctory is the directory in which you want to create the content directories.

4.	Repeat the command for each RealAudio format you encoded.

For example, typing the command:

raconv /28_836files/mozart34.ra /music

creates the directory /music/mozart34.ra, moves the file mozart34.ra from the 28_836files directory to this new directory, and renames the file 28_8.36.

If your files are organized by encoding format, you can run raconv on a whole directory by entering wildcards for InputFileName. For example, typing the command:

raconv /28_836files/*.ra /music

This command takes all the RealAudio files in the directory 28_836files and creates new directories and files under the directory /music.

The raconv utility does not create or overwrite a directory if it already exists. This enables you to run raconv on files in one format to create the directories and then run raconv on files in other formats and place them in the appropriate directory.

Bandwidth Negotiation Explained


 Settings File Format

The settings file specifies the compression type and the title, author and copyright strings for the .RA file.  This parameter is optional.  If not specified, the settings are those most recently stored by selecting Save Default Settings from the Options menu.

A settings file must be a text file with the following format:

[Default Settings]

title = title string here

author = author string here

copyright = copyright string here

Compression = <Compression Type>

PerfectPlay = <0 for disabled or 1 for enabled>

SelectiveRecord = <0 for disabled or 1 for enabled>

Note: The settings file must start with the [Default Settings] line.

Compression Types:

lpcJ 0	RealAudio 2.0 - 14.4
28_8 0	RealAudio 2.0 - 28.8
DNET 0	RealAudio 3.0 - 28.8 Mono, narrow response
DNET 1	RealAudio 3.0 - 28.8 Mono, medium response
DNET 2	RealAudio 3.0 - 28.8 Mono, full response
DNET 3	RealAudio 3.0 - 28.8 Stereo
DNET 4	RealAudio 3.0 - ISDN Mono
DNET 5	RealAudio 3.0 - ISDN Stereo
DNET 6	RealAudio 3.0 - Dual ISDN Mono
DNET 7	RealAudio 3.0 - Dual ISDN Stereo


 Source Audio

The RealAudio Encoder compresses the audio data stream and prepares it for use with the RealAudio Server.  This compression is lossy, which means that some of the information contained in the original audio data stream is removed.  To ensure that you will get optimal audio quality after encoding, you must start with a high fidelity recording which utilizes the full dynamic range and has a high signal to noise ratio.  Using Digital Audio Tapes (DATs) or Compact Discs (CDs) as your source, for example, will result in high quality RealAudio files.  In addition, you will have better results if you use simpler audio signals rather than very complex signals.

While it is possible to record directly from a source, pre-processing the audio file before encoding contributes to higher quality sound.  For example, a closely miked interview in a studio will encode better than an interview conducted on a busy or windy street.  For an in-depth discussion concerning pre-processing audio, see Getting the Best Sound Out of RealAudio on the Progressive Networks Web site at:

http://www.realaudio.com/help/content/audiohints.html

There are a number of shareware software packages available for recording sound;  you can search the Yahoo directory at:

http://www.yahoo.com/Entertainment/Music/Genres/Computer_Generated/Music_Software

Getting the Best Sound Quality

Supported File Types and File Extension

Live Sound Quality


Audio Quality
 Getting the Best Audio Quality

To achieve the highest possible audio quality, the input file should be 16-bit (instead of 8-bit) and must use the full range of available amplitude (dynamic range).  The following picture demonstrates how the amplitude indicator should appear in your audio editor or recording application.

Figure 1

When recording audio, first adjust your input levels so that the amplitude peaks reach but do not exceed the maximum input level. Clipping, exceeding the maximum input level, is heard as a pop or a click in the resulting file. Clipping can result in high-frequency background noise or static in the RealAudio file.

Sound files that do not use the full amplitude range will produce rough sounding RealAudio files.  If the amplitude range of an existing file is too low, you can use your audio editors Increase Amplitude or Increase Volume command to adjust the range before encoding the file.  Better quality will be achieved, however, if the levels are correctly set at the time of recording.  Some audio editors have a Normalize function that will maximize levels automatically.

If your audio editor has a compression filter, additional improvements can be made by compressing the signal.  This automatic level-control decreases the difference between quiet and loud sections of the audio file.  There are no hard and set rules, and each file will require a bit of experimentation; however, this step will help make quiet sections of your audio more audible.  Check your audio editor manual for additional hints.


 Live Source

Live audio is audio that comes directly from your sound card, either through microphone input or line input from an audio device such as a CD player.  Encoding live audio requires particular attention to the real-time requirements and to quality criteria to ensure that the encoded results match your quality expectations.

Live Sound Quality

System Performance

Configuring Systems for Encoding Live Audio

Windows 95 Performance Options


 Live Sound Quality

Recording audio to a digital audio file before encoding allows you to use a sound editing tool to inspect and edit the recording to improve the quality of the RealAudio encoded file. For example, you can splice segments of the audio, adjust amplification, and apply various filters.  Live audio does not provide this adjustment opportunity, so it is very important to test and adjust your hardware configuration and software settings before the actual encoding session.

As with all professional audio recording, setting input levels is crucial for ensuring high fidelity.  For more information see Getting the Best Audio Quality.  Using high-end equipment (such as a good microphone) or high quality recordings (such as a CD or DAT) will substantially improve the quality of your recording. You may also wish to apply external sound conditioning hardware such as an equalizer or compressor to prepare the input signal for the sound card.  Additional information on this topic is available in the FAQ section of the RealAudio Web site at:

http://www.realaudio.com/help.html


 System Performance

Encoding live audio requires a computer with sufficient performance to encode in real-time or faster.  A Pentium-class computer with at least a 75 MHz processor is recommended, although actual performance depends on sound card CPU usage and other machine configuration variables.  The RealAudio Encoder displays a status message below the signal window that indicates the percentage of buffers in use.  If this number rises steadily, the PC is unable to process the audio quickly enough to keep up with the real-time input stream.  When the percentage reaches 100%, the Encoder will display an error message indicating that it is unable to continue.

Requirement	File Encoding	Live Broadcasting
CPU:	486/66 DX	Pentium/586, 75 MHz
RAM	8 MB	8 MB required 16 MB recommended
Hard Disk Space (software)	1 MB	1 MB
Sound Card	16-bit sound card capable of recording an 8 kHz signal


 Configuring Systems for Encoding Live Audio

When encoding live audio, other tasks that consume processor time or system resources may cause the audio to skip or pause.  We recommend that you do not perform other tasks on the PC during the encoding process.  In particular, disable the following types of applications:

•	Automated tasks, such as the Windows 95 System Agent.

•	Screen savers

•	E-mail or other applications that can cause spontaneous network bandwidth consumption


 Windows 95 Performance Options

Computers running Windows 95 may require more than 16 MB Network Server memory.

To setup your computer as a Network Server:

1.	In the Control Panel, click System.

2.	Select the Performance tab.

3.	Click File System.

4.	In the Hard Disk tab, set the Typical use of this machine option to Network Server.


 Troubleshooting

For the latest help information please access our help pages at:

http://www.realaudio.com/help.html


Frequency Response

Frequency response describes the spectrum of frequencies present in an audio signal.