Audio File Formats Explained

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INTRODUCTION
There are many different audio file formats and the topic can be confusing when new to recording. Let me try to simplify it by explaining the most common formats you are apt to run into: .mp3, .aif, .wav and .aac (can have the extension .m4a). The major differences between these file formats are how big the files are and how good they sound. As a general rule, the bigger the files, the more audio detail they contain, and the better they sound.

.AIF and .WAV
The .aif and the .wav file formats are “lossless” formats, meaning that (in theory anyway) they sound pretty great. Back in the early days of computer audio .wav files were used in Windows and .aif files were for Macs, but they are the same quality and are very popular for use in recording software because they are the highest quality sound files. The downside to these file types is that they are larger sound files, so they take up more room on your hard drive(about 10MB for a minute’s worth of music), take longer to upload and download to the internet, and because of their size, almost never work as attachments to email.

.MP3
The .mp3 file format was essentially invented to shrink a files size to save space and make it more practical for uploading and downloading audio to and from the internet. The files are shrunk by dropping information from the audio program using a process called “lossy compression”-thus trading the quality of the file for their smaller size. mp3’s come in different sizes and quality because they can be compressed at different bit rates, usually referred to with a number followed by kbps (kilobits per second). The easiest way to think of this is that lower bit rates make smaller files because smaller files contain less information. The most common mp3 format is 128 kbps which was the original ITUNES file format – it is 90% smaller than the same file in CD format! Many files are now available from online sources as .mp3 256 kbps. And as you would expect, they use 2x the amount of space to represent the audio and so they are a higher quality format. Twice as good I guess. By the way, I would not use the .mp3 audio format for recording tracks for your music. In addition to being of lower quality, they do not sync well. (More info on that in future DIYs.)

AAC
The aac(.m4a) file format is the latest generation of audio formats from the same people who invented the .mp3 and is actually technically an offshoot of .mp4. However, the folks behind this format wanted to give it a snappier name so they came up with aac, which stands for Advanced Audio Codec. It is considered to sound superior to .mp3 at equal bit rates and when it became available it is the format APPLE chose to use as the default in iTunes.  Many people consider audio files compressed with aac at 330 kbps to be almost indistinguishable from CD quality. I think this format sounds pretty good and I store all of my music from my CD collection in this format to save room on my hard drive.

BIT DEPTH AND SAMPLE RATE
2 more file descriptions you’re going to run into are bit depth and sample rate. Without getting into detail about what these mean, let me make a generalization: whether you’re talking about .mp3s at 128kps vs 256kps, or 16 bit depth vs 24 bit depth, or 44.1khz sample rate vs. a 48khz or 96khz sample rate rate, the higher the number, the better the quality and the more storage and computer processing power the file will require. In regards to hosing between 48khz and 44.1khz sample rate, it’s your choice. Personally, I have been sticking with 44.1khz since that’s the standard used on CD’s and I don’t feel there’s a sonic advantage to 48khz.  However, music supervisors often request tracks at the 48khz sample rate. Conversions can be done on the final mixes if need be, but, it is very important that  everyone working on the same project is using the same sample rate in the recording process. Files recorded at 44.1khz and played back at 48khz (and visa versa) will actually playback at a different speed and pitch!

CONVERTING AUDIO FILE FORMATS
Converting your song file from a lower quality audio format to a higher quality format will not make it sound better!
Much like blowing up a low quality picture file to larger size does not make it look better, it only makes it bigger. Start with the highest quality file you can and convert down to decrease file size. Once a file is converted to the smaller format, the information discarded to make the conversion is lost and will not return just because you convert it back to a higher rate. All of these file formats can be created using ITUNES. Please checkout “DIY#2-ITUNES:FILE CONVERTER AND DATABASE” for more information.

SUMMARY
For recording and overdubbing in your recording program:
I recommend you use the .wav format at 44.1 khz or 48 khz, and 24 bit. Feel free to use .aif at the same values or, if you really have a grip on this stuff, move up to a 96 khz sample rate(but not unless you have a pretty new computer with plenty of speed, ram and storage). The higher 24-bit rate is what really keeps all the behind-the-scenes math in your audio software sounding clean, so I highly recommend you stick with 24 bit recording and use .wav or .aif files.  Set these as your preferences in your recording program before you start recording.
For attaching demos, rough mixes, etc to emails where the sound quality is not a big issue, use MP3 128 KPS and only attach one audio file per email.
For uploading to Soundcloud or your web site:
or anyplace else where the music will be streamed, try 256KPS mp3. Sounds pretty good, streams well.
Copyright 2014 Crit Harmon

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