Podcast Academy

In this segment I will focus on file formats and transfer efficiency.

Many of us are members of organizations and/or networks. Some of us produce programs for clients. In this case we are faced with the inevitable task of transferring large files to and from various peers or logistical locations. Before I discuss my recommendations, it is important to make sure that we understand a few important facts in terms of file formats and their characteristics.

I think it is safe to say that *most* podcast producers realize that WAV and AIFF files are uncompressed, lossless files that yield exceptional quality. They are the recommended file formats for recording audio, and they integrate seamlessly with a vast array of post production applications.

MP3, or MPEG-1 Layer III is a compression codec that is specifically designed to produce a file that is prepared for final delivery. An MP3 file should never be converted back to an uncompressed file format and subsequently re-encoded to MP3, especially if the original MP3 was encoded using a low bitrate. In this case the results would be detrimental. That being said, if you present your MP3 encoder with a good quality uncompressed master and choose your encoding parameters wisely, the resulting file will be a fraction of the size of the original and it will provide excellent results in terms of sonic quality.

As noted above … if transferring and/or exchanging large files slated for post production is a necessity within your work flow, what is missing? The answer is an intermediate file format. Best case scenario would allow us to convert files into a format that would yield a substantial reduction in size in order to maximize exchange efficiency, and at the same time have very little affect on the quality of the original uncompressed master. Enter MP2 …

Let me stress that where MP3 = MPEG 1, Layer III … MP2 = MPEG 1, Layer II. This is not the same file format as the common MPEG-2 video codec/file format. The MP2 codec is widely used within the professional world of commercial broadcasting as an intermediate file format. An uncompressed file converted to MP2 will be approximately 75% less in size compared to the original. The key here is that when the file is converted back to its native state, most - if not all of the original fidelity will be retained. It’s not 100% lossless, however I promise that you will be pleasantly surprised with the results.

Based on your platform there are various software applications that are necessary in order to develop a work flow. Here are the tools that I use: to convert WAV files to MP2, I use the MP2 Encoder available at The Public Radio Exchange [PRX.org]. Mono files will be converted to MP2 at 44.1kHz, 128kbps and Stereo files will be converted to MP2 at 44.1kHz, 256kbps. The encoder is available for Mac and PC.

To convert MP2 files back to WAV [or AIFF], I use a nifty $10 encoder/converter called SoundConverter. This is a fantastic piece of software and it is highly recommended.

A few closing thoughts: I suggest that you look into joining PRX. It’s a tremendous resource. Lastly, I utilize the referenced MP2 concept and work flow for all the file transfers that I participate in [clients, IT Conversations, personal projects, etc]. Try it and let me know what you think …

-ptfigg.