Creating Podcast Audio

IMPORTANT:
We always recommend you keep a high quality original of the audio file and make an optimised copy for web distribution. That way if in the future you want to burn CDs or reoptimise to a different format you can go back to the high quality source file.

There are so many devices that can help you capture audio (e.g. a talk). However, often the files generated are going to be too large for distribution across the web. To solve this problem the audio files need to be optimized correctly. Optimization simply means changing the file to the right settings which produces a more compact (compressed file). The most popular format for distributing audio files on the web is MP3. Note just because a file is an MP3 does not mean it is optimized properly. Whilst technically speaking it is does not necessarily provide the best balance between file size and quality (MP3 files tend to be a bit larger for the same quality compared to some other formats) it is so widely used in all sorts of devices that to ensure everyone can hear your files where correctly it is probably the best solution at this time. Please ensure you always have the permission of the copyright holder before uploading any files.

Different Audio Sources

Depending on what method you use to record your audio you may start with a different source:

  • Tape
    If you are currently recording on normal audio tape we would urge you to upgrade to a portable digital recorder, they are fairly cheap and will make the process significantly easier. Due to the complexities and quality issues we do not recommend or support using this method.
  • Audio CD - see CD optimization
    Your sound desk may output straight to CD. The CD should be very high quality and a useful master source.For optimization instructions see below.
  • Digital Recorder (e.g. portable MP3 recorder) - see File optimization
    You may output directly from your sound desk to a digital recorder. This will be great for producing a file that can either be uploaded straight away or (most likely) be used to provide a file for optimizing.
  • Recording to Hard Disk (e.g. direct to PC or Laptop) - see File optimization
    This is essentially the same as recording to a digital recorder. It will produce a file you can the optimize for upload.

iTunes (PC and Mac) - CD & File Optimization

iTunes enables you to optimize an existing file or rip straight from a CD creating a file ready to distribute across the web. You can download iTunes free of charge from http://apple.com/itunes/download. If you need any help with the installation please contact the Helpdesk

IMPORT SETTINGS (very important)

  • Open iTunes
  • Go to the Preferences options (on the PC these are under the Edit menu or may be found by clicking the small down arrow at the top left of the screen or by pressing the Ctrl key and the , key at the same time)
  • Click Import Settings button
  • Set Import Using to MP3 Encoder
  • From the Setting tab select Custom
  • In the MP3 Encoder setting box set them as shown

iTunes

When you press OK you should see something similar to this

iTunes Import Settings

Despite setting a 32 kbps Stereo Bit Rate (as you are using mono) the confirmation box should show 16 kbps (mono) and VBR, if not then go back into the custom settings and verify your configuration above. Note you may not need to have error correction checked (feel free to try without).

From an Audio CD

Once you've set the import settings for iTunes (as above), simply insert an Audio CD, iTunes will offer to add it to your library and convert the file on the fly. Once complete eject the CD and then look in your Library (probably under music). You can search for the file in the search box if you can't find it. Double click on the file to play it and check you are happy with the quality. If when you listen to your recordings they aren't of a high enough quality then you can try again setting the Stereo Bit Rate in iTunes to 64 kbps (leave the other settings as they are) - this will create a better quality audio file but it will be twice the size and therefore take twice as much space in your account and take twice as long for your visitors to download! You could try the Stereo Bit Rate of 64 kbps and lower the quality to find your perfect compromise on size and quality. You should never set the Stereo Bit Rate in iTunes above 64 kbps when making optimized versions of spoken audio and mono should always be selected.

From an Existing Audio File (and crop any unneeded audio)

Once you've set the import settings for iTunes (as above) you can easily convert any audio file in your iTunes library.

  • Open iTunes (if not already open)
  • Simply find the file in iTunes library (near the top left of the screen ensure it is set to Music). This will show your music library (which includes any ripped audio files). You can search for a file by name using the search box at the top right. The file should show in the track listings (the bottom half of the window).
  • If you wish to crop (remove unneeded audio from start and finish of recording) follow these extra steps):
    1. Right click on the file and select Song Info. Click on the Options Tab
    2. Tick the Start Time box and type in the time you want the audio to start from (e.g. if a particular speaker starts 45 mins and 23 seconds into the recording enter 45:23) then tick the Stop Time box and enter the time you want to stop the audio, e.g. 55:25 (55 mins 25 seconds)
    3. Click OK
  • Depending on your version of iTunes the option location varies. Either click on the file (in the list of tracks) and then

    under the File menu go to Convert then select Create MP3 Version or
    under the Advanced menu at the top select Create MP3 Version or  
    right click on the file and select Create MP3 Version (see screenshot below)

iTunes Create MP3 version

  • Wait until the new version appears in the iTunes library
  • You should now see two files with the same name in the library. To upload the correct one you'll need to know which is the optimized file and where it is stored. You do this by right clicking on the files, selecting Song Info and then making sure the settings shown on the File tab show the smaller file size and the correct optimization e.g. Mono and a low bit rate (must be not more than 32kbps). If the file info is not showing this then close the info box and try right clicking the other file. Once you've found the correct file make a very careful note of its filename (you do not want to upload the non-optimised file by mistake).

 

Adding Track Information

You can view and edit the track info. Right click on the relevant file in the iTunes library and select Get Info (sometimes called Song Info or similar) , the box similar to the one shown below will appear.

iTunes Get Info

We optimised an audio book CD which already contained information about the Author, Publisher, Title, etc. If you recorded the CD yourself what you see above will vary. Note it says the file is of Kind: MPEG audio file this is an MP3 file (MP3 is part of the MPEG standard). Our audio book was nearly 45 minutes long but optimised down to 6.5MB (a poorly optimised version could have been 100 MB, which would take far too long to download). You can see the bit rate says 20kbps (not the 16kbps we specified) that's because we used Variable Bit Rate and the 16kbps is the minimum it will use. Assuming you were importing a file that is mostly talking then it is useful to check the Channels is correctly set to Mono. Lastly you can see where the file is stored on your computer. You may want to note that down as you will have to locate it shortly to upload it to your website.

Before we upload the file we recommend you add extra information. This information will be very useful to people who download your file. Especially when searching for it on their computers, playing it on portable devices or cataloging their collection.

Click on the Info or Details tab (depending on your version)

iTunes InfoTab

You can edit the content of any of these boxes to make sure the information is complete and accurate. The information will be saved as part of the audio file and therefore always stay with it. 

Windows Media Player (ripping a CD)

  • Open Windows Media Player
  • Press Alt on your keyboard
  • From the menu select Tools -> Options -> Rip Music
  • From the Format drop down option select Windows Media Audio Lossless (to make perfect quality master file to optimise from). Note if you rip CDs you do not wish to optimize for the web remember to return this to the original setting as required)
  • Make a note of the ‘Rip music to this location’ info (this is where the files will be saved. You could change the destination if required
  • Click the File Name button, select the file naming options as required and under the Separator drop down select – (Dash) then click OK
  • Click OK again
  • Then click the Rip tab
  • Insert your CD in the drive and click the Rip button
  • Once the ripping is complete you will have really good quality files on your hard disk that you can convert to web optimized audio files. See iTunes optimization information above.

Other Programs

There are many other programs you could use to optimize your file for web download. Whatever way you make your MP3 files we would recommend you start by optimizing your source file to 16kbps (mono). If this is acceptable quality then upload that. If you don't like the quality then try 32kbps (mono). If your MP3 encoder supports Variable Bit Rate (VBR) you may wish to try using this. VBR enables the encoder to control at what points the audio needs more information (increasing the bit rate) and at what points it can reduce the bit rate - this can give good file size savings (making smaller files) whilst keeping the quality high. A program commonly used to optimise audio is Audacity with the Lame MP3 encoder. However, at this time there are concerns over whether or not the Lame MP3 encoder may be infringing on patents and therefore we have reservations in recommending it. Audacity is totally free and therefore that is fine to use for recording and editing files. If you carry out your own research and are happy to use Lame MP3 encoder then you may find the information below useful: 

You can download Audacity from http://audacity.sourceforge.net. There are versions available for Windows, Mac OS 9 or X, and Linux/Unix.

If you want to export MP3 files (you probably do) then either you'll have to install the LAME MP3 encoder, see instructions here: http://audacity.sourceforge.net/help/faq?s=install&item=lame-mp3  or you can create and edit files in Audacity and then use iTunes (see above) to convert the file to MP3.

You can either record directly into Audacity or you can use it to process prerecorded audio files.