Demystifying Audio Formats: What Format Should You Record In?
This is a guest post by Rajiv Agarwal. If you want to contribute a post, please see the guest post guidelines.
There are so many audio formats out there, which ones should you choose to record your audio in?
An audio format is a file format that you use to store music on your computer. There are a variety of formats, like wav, mp3, aiff, wma etc.
To understand the difference between various formats, we need to first understand terms compressed and uncompressed formats.
Uncompressed Audio Formats
Uncompressed audio formats are bulky files and take up considerable space on your hard disk or storage drive. The advantage of uncompressed audio formats is that the quality of the digital audio remains intact, as it is unchanged. It provides exactly the same quality; no matter how many times you process or re encode it.
Compressed Audio Format
Compressed audio formats compress the digital audio data, resulting in smaller files. You can free up valuable space on your hard disk by using compressed audio formats.
Compressed audio formats are further categorized into 2 two groups:
1. Lossless Compressed Audio Formats
These audio formats compress digital audio data, but there is no loss of data or degradation of audio quality during the compression process. The finest example of such format is FLAC.
2. Lossy Compressed Audio Format
These audio formats compress digital audio data, but are known to eliminate certain information and frequencies to reduce the file size. Lossy compressed audio formats causes degradation in audio quality. The difference in audio quality can be large or small, depending upon how much data has been removed.
Also, each subsequent processing or re encoding will result in more quality loss. The classic example of lossy compression is MP3.
Which recording Format is the best for me?
To choose the best recording format, we need to understand 2 more terms, Sampling and bit rate.
Digital audio has two primary qualities that compose the way the audio is described. – sampling rate and bit rate.
When you are recording audio digitally, the device (say, your computer) receives the audio signal, by breaking it up into “snapshots” or samples.
In recording technology, the number of samples received per second is called the sampling rate. The camera that records a number of image frames per second and plays it back as a continuous moving image.
Similarly, you listen to uninterrupted audio playback. Sampling rate is measured in hertz and represents the sound frequency range.
The higher the sampling rate, the greater is the audio quality and ensures greater precision in your high notes and low notes.
Standard CD quality incorporates a sampling rate of 44, 100Hz or 44.1 KHz. Sampling rates start from 8000hz(very very low quality) to 196,000(very very high quality, with extreme huge files).
In digital multimedia, bit rate often refers to the number of bits used per unit of playback time to represent a continuous medium such as audio.
Let us understand what the bit rate actually represents.
While sampling rate is number of samples recorded per second, bit rate refers to the characteristics of each individual sample recorded. Going back to the digital camera example, bit rate is the equivalent of pixels in digital images.
Higher the pixels, the better the image quality. Similarly, higher the bit rate (also called bit depth), better is the audio quality. For instance an 8 bit audio will sound grainy and harsh, while a 16 bit audio sounds much better.
Standard CD format has a 44.1k sampling rate combined with a 16 bit rate.
Naturally a 24 bit audio will offer higher quality, but such files occupy more space and require greater computing power to process and may not be really necessary for the purpose of your audio.
Professional audio studios opt for 24 or 32, or even higher bit rates, depending on the computing power, because the higher accuracy it offers is useful in the recording, mixing and mastering process.
Bit Rate in MP3
The MP3 format is a lossy audio format that compresses audio files to reduce size by eliminating redundant data.
You can choose how much information an MP3 file will retain or lose during the encoding and compression process by tweaking the bit rate. Lower bit rate means that the encoder will discard more information during the compression process, which may affect the audio quality on playback. Bit rates for MP3 encoders range from 16 kilobytes per second (kbps) to 320 kbps.
A bit rate of 320 kbps is closest to CD quality audio and is similar to what you’d hear on the radio. A higher MP3 bit rate provides better audio quality but produces larger files.
Charts comparing various formats and the quality vs size.
|Wave/Aiff||8,000hz-16,000hz||8||Very Low||Very small|
|48,000Hz and Above||16 bit -32 bit||Pristine||Very large|
|MP3||8,000hz-16,000hz||16-96 kbps||Very Low||Very small|
|32,000-44,100 hz||96-196 kbps||decent||Small|
|44,100 Hz||256-320 kbps||Good||Medium|
So what do you choose for recording your audio?
For pristine quality, always record in uncompressed formats like wav or aiff, at atleast 44,100 khz and 24 bit. Any subsequent processing like mixing, editing etc will not result in any degradation of the quality.
If you need to encode/record in mp3, at least 196kbps is minimum for a decent quality, though 320 kbps is always the best.
Some of the commonly used audio formats include the following:
1. WAV Format
The WAV audio format stores uncompressed audio data on Windows computers. It is based on the RIFF bit stream format method of storing data.
Since it stores uncompressed audio data, it retains the 100% original audio quality and is popular among audio experts. The WAV format can be easily edited using software.
2. AIFF Format
The Audio Interchange File Format (AIFF) developed by Apple Computers is an uncompressed audio format commonly used for storing audio data on Apple Macintosh systems.
Because it stores uncompressed audio data, the AIFF format is also commonly used for professional audio applications.
3. MP3 Format
The MP3 format is a commonly used lossy compression audio format. It essentially reduces the file size by omitting data in the file.
By using perceptive audio coding and psychoacoustic compression, the MP3 format retains the quality as close to the original as possible.
Therefore MP3 is the commonly used audio format for storing large number of songs on your computer without taking up too much space with acceptable quality. Never record in MP3, unless you have no other option. Always record in uncompressed formats like WAV/AIFF and THEN CONVERT to Mp3 file of desired size.
4. AAC Format
The Advanced Audio Coding (AAC) format, another lossy compression audio format was developed to be the successor of the MP3, as it offers better audio quality than the MP3 at lower sizes.
It is the standard audio format in Apple’s iTunes and ipods.
5. WMA Format
The Windows Media Audio (WMA) format is a lossy compression audio format designed by Microsoft to compete against the MP3.
However, the MP3 stills retains the top spot in popularity. The lossless compressed version of the WMA format called WMA lossless is also available that reproduces the original audio quality, with zero elimination on decompression and play back, similar to wav or aiff.
Rajiv Agarwal is sound designer, music composer and mastering engineer. His studio delivers Audioshapers professional audio mixing, mastering and audio post production solutions.
Image by: Magic Trax