Real Audio:
Details and Overview 2

Source Files

RealAudio content may be created either from previously recorded digital audio files or from an external audio source. The Encoder does not support compressed input files. Use a sound-editing utility to convert non-supported formats to a supported format.

The following inputs are supported:

Type

Platform

Sample Size

.wav audio

Windows, UNIX

8- or 16-bit mono or stereo

.au audio

Windows, UNIX, Macintosh

8-bit m or stereo or 16-bit linear mono or stereo

.pcm audio

Windows, UNIX

8- or 16-bit mono or stereo

.snd audio

Windows, Macintosh

8- or 16-bit mono or stereo

.sd2 audio

Macintosh

8- or 16-bit mono or stereo

.aiff audio

Macintosh

8- or 16-bit mono or stereo

Live feed

Windows Live, Mac Live, UNIX Live

8- or 16-bit mono or stereo

Note: You can use a stereo input file to produce a mono or a stereo output file. However, you cannot use a mono input file to produce a stereo output file.

The valid sampling rates are: 8 kHz, 11.025 kHz, 16 kHz, 22.05 kHz, and 44.1 kHz.

Producing Higher Quality Sound

The quality of your RealAudio clips depends on the quality of the input source. Because the RealAudio compression algorithms are lousy, some of the information contained in your original audio input will not be included in the reconstructed signal sent to the RealAudio Player. You produce higher-grade audio following compression/decompression if you start with a high-fidelity recording with full dynamic range and a high signal-to-noise ratio.


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Encoder for Macintosh

 To encode a file with RealAudio Encoder for Macintosh:

  1. Select a previously existing audio file to convert into the RealAudio format, by clicking Input.

     

  2. Select the file you want to compress from the Directory window and click Open. When you open a file, the Sampling Rate, Duration, Size, and Compressed Size appear at the top of the window.

     

  3. Enter Title, Author, and Copyright information for your RealAudio output. These fields appear both within the main Encoder window and within the Preferences window. If you do not want to establish default values for this information, enter the information in the Encoder window.

    Note: If you plan to encode multiple files with the same information, you can save time by using the Preferences window to specify information that is common to all of your files, such as Copyright. Access the RealAudio Preferences window by choosing Preferences from the View menu. Refer to Macintosh Preferences Window.

     

  4. In the Encoder box, choose the encoding algorithm for this file. A description of the chosen algorithm appears in the Encoder Description field.

     

     

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

     

  6. 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.

     

  7. Click the Encode button to start the encoding process.

     

  8. Select folder and filename for the output file in the Directory window. While the file is encoding, the Progress bar at the bottom of the RealAudio Encoder window indicates what percentage of the file is encoded.

     

  9. Verify the encoding by playing the newly created file with a RealAudio Player.


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Macintosh Preferences Window

The Preferences window displays the default settings used by RealAudio Encoder. Information that you enter here is saved when you close this window. Do not enter information into the Preferences window unless you intend to set default parameters for encoding.

Feature

Description

Title

Sets the default Title.

Author

Sets the default Author.

Copyright

Sets the default Copyright.

Encoder

Sets the default Encoder algorithm.

Background Loops

The number in this field controls how the Encoder shares CPU time with other active applications. The default is set to 10 for Power PC Macintoshes. The higher this value is set, the faster files encode. However, your computer will be less responsive if you switch to other applications.

Note Macintosh 680x0 users may want to set this field to 1.

Ask for RA Header Info

Select this check box to have a window appear before each file encodes. This gives you the opportunity to specify new Title, Author, and Copyright information for each file.

Ask for Save File Location

Select this check box to have a Save File window appear as each file is encoded so you can specify the folder and filename for the RealAudio output file.

If you do not select this check box and are encoding multiple files, the RealAudio files are saved in the same folder as the input file, with the .ra filename extension added.

Enable Selective Record

Select this check box to allow RealAudio Player Plus users to save your RealAudio clip to disk.

Enable PerfectPlay

Select this check box to allow RealAudio Player Plus users with 14.4 Kbps modems to play RealAudio files encoded for a higher bandwidth by partially downloading audio data before beginning playback.

Drag-and-Drop Encoding for Macintosh

RealAudio Encoder for Macintosh supports drag-and-drop encoding. You can drag and drop input file icons onto the RealAudio Encoder icon. This automatically encodes files using the default output filename and the most recently saved encoding preferences. If you have selected the Ask for RA Header Info check box or the Ask for Save File Location check box, you are prompted for information as each file is encoded.


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Editing

If you want to edit your sound files, you have two options-you can edit your .ra files, or you can edit your original source files.

Input Files

This is the editing method of choice. Encoded Audio is stored in indivisible clips of varying duration depending on the encoding algorithm. This limits how precisely encoded audio can be cut and pasted. Sound editing software can cleanly and easily cut and paste .wav or .au files, and there are numerous programs that provide such features as mixing (adding background music to a vocal segment) and fading in or out.

RealAudio Files

RealAudio Encoder is distributed with two editing tools utilities, Racut and Rapaste, which enable simple editing of RealAudio files. The Racut tool cuts specific portions of a RealAudio file. The Rapaste tool combines two or more RealAudio files (encoded with the same algorithm) into one file.

Encoded Audio is stored in indivisible clips of varying duration depending on the encoding algorithm. This limits how precisely encoded audio can be cut and pasted. This is a compelling reason for editing the original source files rather than RealAudio files. The following table lists the indivisible duration for each encoding algorithm:

Encoding Algorithm

Duration

RealAudio 2.0 - 14.4

.02 seconds

RealAudio 2.0 - 28.8

1.4 seconds

RealAudio 3.0 - 28.8 Mono, narrow response

.139 seconds

RealAudio 3.0 - 28.8 Mono, medium response

.139 seconds

RealAudio 3.0 - 28.8 Mono, full response

.192 seconds

RealAudio 3.0 - 28.8 Stereo

.192 seconds

RealAudio 3.0 - ISDN Mono

.070 seconds

RealAudio 3.0 - ISDN Stereo

.096 seconds

RealAudio 3.0 - Dual ISDN Mono

.035 seconds

RealAudio 3.0 - Dual ISDN Stereo

.048 seconds

Editing RealAudio Files on Macintosh

Copying Selected Portions of RealAudio Files

Use RACut to create a copy of a selected portion of a RealAudio file.

To create a copy of a selected portion of a RealAudio file:

     
  1. Listen to the file and use the time display of your RealAudio Player to determine the start and end times of the segment you want to capture.

     

  2. Click RACut on the Process menu of the RealAudio Encoder.

     

  3. Click Input to browse for the .ra file from which you want to copy a segment.

     

  4. Select your source file in the Directory window and click Open. Once you have opened the file, the RACut window displays its header information.

     

  5. Type the limit times for the segment you want in the StartTime and EndTime text boxes. If the segment you want extends to the end of the file, click EOF.

     

  6. Click Process; you are prompted for the name of the new file. Type the new name and click Save.

Combining RealAudio Files

RAPaste creates a new RealAudio file that is a compilation of two or more existing RealAudio files.

To paste together multiple RealAudio files:

     
  1. Click RAPaste on the Process menu of the RealAudio Encoder

     

  2. Click Add to select .ra files you would like to combine. Each file you select is added to the Paste list in the RAPaste window.

    Click Change to modify a particular file in the Paste list. Click Delete to remove a file from the Paste list. Click Delete All to remove all of the files from the Paste list.

     

  3. When the list of files is complete, click Process. You are prompted for the name of the new .ra file. Enter the name and click Save.

     

  4. Use the RealAudio Player to verify the content of the new file.


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