How to Master Podcast Editing

When producing a podcast file that you’ll put on your website, you need to convert the original mastered audio into a smaller format – this will involve some podcast editing on your part. Once you get a hang of podcast editing and the most suited formats, you will be well on your way to podcasting like a pro!

Whether you are going to outsource your audio editing, or do it yourself, there are two main audio formats that you should use for podcasts: MPEG3 (MP3) and M4A/AAC. Both are referred to as lossy codecs – they basically remove data to make a smaller file.

In this article

1. MPEG3: Motion Picture Experts Group – Layer-3
2. MP3 Basic Tips
3. M4A / AAC: Advanced Audio Codec
4. AAC Basic Tips
5. Check Your Mix – Review your Podcast
6. File Conversion – Converting to MP3
7. Structure for Saving Podcast Episodes
8. File Tips for Podcast Editing
9. Bitrate
10. Sample Rate
11. Codec Quality (optional)
12. Summary – Key Points about Podcast Editing

MPEG3: Motion Picture Experts Group – Layer-3

The standard digital audio format for podcasts is MPEG 1 Layer-3, commonly referred to as MP3. MPEG stands for Motion Picture Experts Group and was developed for the first multimedia content. There are several other audio formats: Layer-1, Layer-2 as well as the most common Layer-3. There are different measures of quality within an MP3 file. As a podcaster, you will want to select a quality that both sounds great but also downloads quickly for listeners.

If your podcast is mostly voice with no background music or musical segments, you may want to consider using a mono file as this will reduce the MP3’s file size and minimize your podcast’s download time so that your listeners can get to listening even faster.

MP3 Basic Tips

• Do not host your media on the same server as your website. The large media file downloads can cause your website to come to a crawl the first few hours after you release your episodes.
• Make sure your files have the appropriate file extensions (e.g. file.mp3). Applications like iTunes and others determine the file content type based on the file extension.
• Applications Supported: Nearly all applications can play this format.

M4A / AAC: Advanced Audio Codec

The Advanced Audio Codec was designed as a replacement for MP3 with the main focus being to reduce the file sizes of lower bit-rate recordings. It was first adopted by Apple who standardized their iTunes software around the format. At lower bit-rates, an AAC encoded file will sound better than an equivalent MP3.

Unlike MP3, AAC allows for extensions including Digital Rights Management and linked media. However, support is not as widespread as MP3 and many mobile devices may not support it or the extensions that Apple has added.

Apple’s iTunes software enables AAC encoded podcasts to use chapters, bookmarks, external links, and synchronized images displayed on iPod screens or in the iTunes artwork viewer.

If AAC isn’t one of your export options in your software, you can convert an MP3 into an AAC file by using Apple’s iTunes program, but there may be some additional loss in quality.

AAC Basic Tips

• The industry standard and the official successor to MP3 (also called MP4 audio; most common file extension is M4A).
• Widespread in the Apple and broadcast community (iTunes, iPod, iPhones, set-top boxes etc.), also supported on Android and most desktop audio players.
• Applications Supported: All Apple-based hardware, Android and most PC software.

Check Your Mix – Review your Podcast

See if your mixed down MP3 sounds good on a variety of stereo systems such as your computer speakers, headphones, portable stereo and car stereo. If your mix translates well from system to system, you know that you have created an excellent work of art. Check out these quick tips if you need more help on podcast editing and mixing sound effects into your podcast.

File Conversion – Converting to MP3

Whatever recording program you’re using, you will have the option to save or export your recording as an MP3. If the only option is to export as a WAV file, that’s okay, too. You’ll just have to complete one extra step to convert the WAV file to an MP3 file.

Structure for Saving Podcast Episodes

Here’s a tip: organize your podcast episodes by creating a simple file folder structure.

Save time by getting organized right from the start. Create a file folder in ‘My Documents’ called ‘My Podcasts.’ In your ‘My Podcasts’ folder create new folders for each episode in advance such as ‘Episode 01,’ ‘Episode 02,’ ‘Episode 03,’ etc. Having a defined structure for your podcasts will not only keep you organized but will help you plan shows in advance. Whenever you find an interesting story, come across a press release, or think of a great idea, you can save it directly into the folder for that specific podcast. When it comes to planning and recording future episodes, you will already have some content that you can use as a starting point for your next episode.

When saving your podcast episodes, export your podcast recording as an MP3 file. Save the file as ‘Podcast_Episode_01.mp3’ and be sure to export into the appropriate folder.

File Tips for Podcast Editing

WAV or AIFF files are uncompressed audio formats used by PCs and Macs. The formats have huge file sizes with great quality – typically referred to as CD, studio or master quality.

MP3 or AAC are compressed audio formats that are much smaller (typically a tenth the size of WAV) and are faster to download.

Some programs, like iTunes, can encode audio (convert it from uncompressed to compressed). If you want to know how encoding works technically, here’s what you’d need to set to encode audio:

Bitrate

Measured in kbps, this determines the overall file size and quality. High bitrates produce larger files with better quality, lower bitrates produce smaller files but if music is included, a lower bitrate file  may produce distortion.

Note: Do not use a Variable Bit Rate (VBR). Use a fixed bit rate such as 64kbps, 96kbps, 128kbps or larger.

Here is a list of some the bitrates available and when they should be used:

64kbps – AM radio quality, best for talk only with the exception of speakers who have very soft or deep voices. Record in mono to maximize the sound quality.

96kbps – FM radio quality, best for talk with enough quality to play bumpers and music. Record in mono to maximize the sound quality.

128kbps – Compact disk (CD) quality, best for distributing recordings with music. This is a good starting point for recording in stereo.

192kbps or higher – High quality, however, the amount of quality added is not necessarily worth the extra file size.

Sample Rate

Measured in kHz, sample rate determines the accuracy of the recording. If you recorded your audio at 44.1kHz, you should encode the MP3 at the same value. Higher sample rates will produce larger files.

Note: Use either 22.05kHz or 44.1kHz. Other sample rates will playback in flash-based players incorrectly and will typically make you sound like one of the Chipmunks.

Codec Quality (optional)

This is measured in a numeric scale and varies depending on the codec used e.g. the MP3 LAME library uses the values 1-12. Higher values produce larger, higher quality files preserving more detail.

A note about the sample rate: for the best playback on the web you should use multiples of 11.025kHz (11,025 Hz) and use no more than 44.1 kHz, otherwise you may experience the “chipmunk” effect in Flash-based players. Generally for podcasts you shouldn’t need more than 44.1kHz recordings.

Summary – Key Points about Podcast Editing

It’s easy to make your podcast sound exactly the way that you envisioned it to, with a bit of practice and research. After mixing and mastering your podcast, you will be rewarded with your very own podcast-ready MP3 file that you can host online and grow your listeners. For step-by-step instructions on how to edit your podcast, check out these 10 tips for editing a podcast in GarageBand.