Formats, extensions and codecs: what do they mean?
When it comes to audio files, we can talk about formats, extensions and codecs. In summary, we can say that the format refers to the type of file, identified by its extension (* .mp3, * .wav, * .ogg, * .wma etc), which often tells us how it has been encoded or which one is your codec.
Normally those endings are mixed. But what is important to know is that, as in videos, files with the same type of extension do not always have the same codec and vice versa.
This information is valid so that you do not feel lost in case you do not understand the reason why a software, which normally plays your * .m4a files, does not play another with the same extension, for example.
Such a situation could indicate that the codecs used are different. In that case, the solution would be to use other software to read the file or to convert it (new encoding). This can be done even in video editors.
The variations of formats and codecs depend on the options of the companies that develop the softwares that execute the files. In these cases, there are many things at stake, such as technical specifications and relations with patents.
On the other hand, files are usually divided into two types: uncompressed or compressed.
Uncompressed files
Audio recording equipment usually offers us options to record files without losing any information. These uncompressed files can be generated in various formats and extensions, such as WAV, AIFF, FLAC and ALAC. For those who are familiar with photography, they are equivalent to RAW or DNG.
As they are usually very heavy, using lossless formats in the final product is only recommended in some cases, such as:
when the final product can be processed by the consumer (files destined for sound banks, for example);
when there will be recording on physical media (CD, DVD and Blue-Ray);
or for the audiophile market (for a matter of perceived value and guarantee of high quality).
But, even if you don’t want to end the process with a WAV (one of the most common), lossless formats can be very useful at the editing stage. Because they contain a lot of information, they withstand more extreme alterations without harming the audio quality.
With plugins, conversions and processing, they can be manipulated more freely, guaranteeing excellent quality, even if a compressed file is subsequently generated.
Compressed files
Most of the equipment available on the market (cameras, cell phones and even audio recorders) usually deliver already compressed files. This type of file is more practical, easier to process, requires less storage space and is very small (in bytes).
Some examples of these formats are: 3GP, AAC, M4A, OGG, WMA and MP3, which is, without a doubt, the best known. Files are like JPEG or GIF in the images field.
Through a complex algorithm, these files are generated seeking to keep only relevant information for our ears. Depending on the compression mode, we can generate an MP3 from a WAV and have a file 10 times smaller, without perceptible alterations in audio quality.
Speaking of MP3, despite its great popularity, it is currently considered an obsolete format, since others, such as ACC (extension .acc or .m4a), make it possible to obtain smaller files and with higher quality.
Even so, MP3 is still widely used, since a large part of the softwares and equipment were developed for this format. So, to talk about compression rates, we will use it as an example.
Compression rate: what is its relationship to audio quality?
Now that you understand that a file can be compressed and maintain sufficient quality for our ears, you should know that the level of compression can vary greatly.
And it is by the value of the compression rate (or bitrate) that we manage to control the file size and, therefore, the audio quality.
For example, a 320 kbps (kilobits per second) MP3 may sound as good as uncompressed audio from a CD or DVD. As the bitrate value decreases, the file size decreases, but the sound losses become noticeable, depending on the audio.
