Archive:Podcasting with Fedora Talk

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This page is outdated and is only retained for historical reference
This page has been superseded by the How to make a podcast page.


This page explains how to set up and record a podcast using the Fedora Talk Voice-over-IP (VoIP) system. This is a "poor man's podcast," in which both audio streams are compressed for transmission across the VoIP system. The audio quality is less than stellar, but it will work for anyone who can connect to Fedora Talk.

Contents

Equipment

This procedure requires you to have appropriate input (mic) and output (speaker/headphone) devices. Most VoIP users prefer to use a Linux-compatible USB headset with a built-in mic and headphones. Many of the Logitech models are known to work well with Linux in general, and Fedora:

Choose a headset whose mic draws USB power if possible. This type of hardware results in a strong, clear voice signal for recording purposes.

Alternately, you might choose a standard set of headphones and use a separate USB-powered microphone. Many models are available for podcasters. Generally if a device works for both Windows and MacOS, it should work with Fedora.

Typically, built-in speakers and microphones on laptop computers provide very poor audio quality, and can cause feedback problems when recording.

Fedora account VoIP information

You must set up your Fedora account's VoIP information to use the Fedora Talk system. To set up VoIP information, visit the Fedora Account System, and select the VoIP link in the navigation menu. Enter the appropriate information and note your assigned extension.

Set up Fedora Talk

To set up Fedora Talk, visit the Fedora Talk page. A video available at the site shows you how to set up Ekiga, a popular VoIP application, to work with Fedora Talk.

When you have finished the setup procedure, launch Ekiga. From the menu, choose Applications > Internet > IP Telephony, VoIP and Video Conferencing.

Make sure the appropriate audio devices are selected for use with your VoIP application.

For this procedure to work, you must use a codec that can be converted to the proper audio format, and which works with Fedora Talk. The recommended codec is PCMU, sometimes called "uLaw" or "mu-Law". In your Ekiga preferences, disable all codecs other than the PCMU codec. This codec works with Fedora Talk.

Set up applications

This procedure uses the Ekiga VoIP application, the Wireshark network capture and analysis tool, and the Audacity audio editor. Install the application with PackageKit.

  1. From the menu, choose System > Administration > Add/Remove Software.
  2. In the search box at the upper left, enter wireshark-gnome and hit Enter or select Find. PackageKit downloads some data from the network and displays the results in the large pane on the right.
  3. Click the checkbox for the package to select it. If the wireshark-gnome package is already installed, the checkbox will be selected already.
  4. Repeat the previous search and select procedure for audacity and ekiga, if not already installed.
  5. Select Apply. PackageKit downloads the package and any dependencies, and performs the installation. You may need to enter the password for the root account to proceed.

Set up network capture

Run Wireshark by selecting from the main menu Applications > Internet > Wireshark Network Analyzer.

A dialog appears asking for the root account password to run in privileged mode. Provide the password so you can capture information from the network interface device.

From the Wireshark menu, select Capture > Options.... Select the appropriate network adapter, often eth0. Then select Capture Filter, and a new dialog appears. From the list in that dialog, select UDP only, and click OK.

Call the other party

  1. Click Start in the Wireshark capture options dialog to start the network capture.
  2. Use Ekiga or another free software VoIP application to call the other party, and carry on your conversation. When you are done, hang up as normal.
  3. Select Capture > Stop in the Wireshark menu to stop the network capture.

Extract the audio

In the Wireshark dialog, move the window to the middle of the capture and look for a line that is labeled with the Protocol "RTP." It might be either of two color schemes. One color represents the forward direction stream, or one side of the conversation, and the other represents the reverse direction or opposite side. Select the line with the mouse.

From the menu, select Statistics > RTP > Stream Analysis.... A new dialog appears. In the dialog, select the Save Payload... button.

In the save dialog, select the .au format, and the forward stream first. Give the file a name of your choice. Then select Save Payload... again, and this time save the reverse stream, again in .au format.

Note.png
Other codecs
If you did not force the audio codec to uLaw, then you may not be able to convert to an .AU format sound file. In this case, note the codec reported by Wireshark, along with the bitrate available in your VoIP application (usually 8 kHz, or 8000 Hz). In the following step, you will need to use the File > Import > Raw selection in Audacity, and choose the correct format parameters to import the audio streams.

Load the streams into Audacity

Open the Audacity audio editor.

From the Audacity menu, choose File > Import > Audio, and load the first stream. Audacity issues a warning but the audio from the .AU format file loads correctly. Repeat this procedure for the second stream. Then edit as desired using the built-in Audacity functions. You may want to save your work in the standard Audacity project format.

When you are finished, use the File > Export function to export the audio as an Ogg Vorbis file. In the file selection dialog, select Ogg Vorbis from the filter list, and set any options desired. Then save the file with the desired name.