Adding RTP Live Audio to a Program

An RTP live audio stream takes analog audio from the line-in or microphone input of the server's sound card, digitizes the sound using a format you specify, and then multicasts the data to listening clients. Audio can also be fed to the sound card through other devices that the card supports, such as compact disc.

You can set the sound format for RTP live audio streams. The sound format determines the quality at which audio is multicast. In general, the higher the quality, the more network bandwidth the multicast requires.

For RTP streams, NetShow supports specific audio codecs only. These codecs are: Microsoft ADPCM, IMA ADPCM, PCM, CCITT G.711(a-Law and u-Law), and GSM 6.10. For more information about the codecs supported, see the NetShow RTP Audio Control SDK in the NetShow Client SDK. The set of codecs that can be used with RTP audio are not the same set of codecs that can be used with ASF audio.

• The recommended sound format for corporate intranets is IMA ADPCM, mono, 8 KHz, 4 bits/sample.
• The recommended sound format for Internet use is GSM 6.10, mono, 8 KHz.
• The recommended sound format for use by VAT clients is CCITT u-Law, mono, 8 KHz, 8 bits/sample.

Note the following:

• The sound format you set on the server must match the format specified by Nsrtpaud.ocx on the client. If the client begins receiving a stream that is in progress, the Nsrtpaud.ocx can automatically detect the sound format. For more information on specifying the sound codec for Nsrtpaud.ocx, see NetShow Client SDK.
• The client computer must also have the format you set installed locally.

To add an RTP live audio stream to a program

1. Under Programs, click Manage Programs.
2. Click to select the name of the program to which you want to add the stream.
3. Point to New on the Stream menu, and then click RTP Live Audio.
4. To give the stream a name and description, click the General tab.

   

   • In the Name box, type a name for the stream.
   • In the Description box, type a description for the stream.
5. To define the source and destination of the RTP live audio stream, click the Source/Destination tab.

   

6. The Source area displays the default sound format and attributes for the stream.

   If you want to change the format, select a format in the Format box, and then select the type of sound you want to use in the Attributes box.

7. In the Destination area:
   • Type the destination IP address in the IP Address box.
   • Type the destination port in the Port box.

     For more information on IP addresses and ports, see Setting Multicast Destination IP Address and Port.

8. Specify the scope of the multicast by selecting a Time to Live option.
   • Click Local Network to limit the multicast to the local network node.
   • Click Intranet to limit the multicast to your site.
   • Click Internet to expand the scope of the multicast to the Internet.
   • Click Other to type a custom value. Values can range from 1 through 255.

     For more information on setting the scope of multicasts, see Setting Multicast Scope.

9. To display the advanced options, click the Advanced tab.

   

   • In the Multicast Adapter Address box, select the address of the network adapter to use for multicasting on your server. If your server has only one adapter, leave default selected. On computers with multiple adapters, you can use this option to multicast separate programs simultaneously by using a different adapter address for each program.
   • To store the audio multicast as a .wav file, click Record To WAV File. Then type the path and name of the file in the WAV File box, or click Browse to locate a path and file.
   • To specify a length of time for the stream to run, click the Duration box, and then type the time in the format hh:mm:ss, where h represents hours, m represents minutes, and s represents seconds. When the time is up either the program ends or, if there is another stream following this one, the next stream starts. If no duration is specified, the stream plays to its end or until the program stops.
10. Click OK.

For more information on setting the source and volume for sound, see Setting the Sound Source and Volume for RTP Audio.

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