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Compressed audio formats

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Compressed audio formats

Compressed Audio File Formats

Understanding compressed audio formats
The digital age dictates its own laws, according to which, in particular, audio and video information is more convenient to store and transmit in compressed form. Let’s briefly discuss the principle of sound compression.

Compressed Audio file formats

As you know, the music we listen to consists of a set of signals, each of which has its own characteristics, including loudness. The human auditory system is designed so that we do not distinguish or misdirect a weak (low) signal from the background of a strong (strong) signal. This principle forms the basis of modern means of compression (compression) of audio data.

If we imagine that a signal of a certain length is divided into many parts, and each part is processed in such a way that a weaker signal, which is difficult to distinguish from a strong one, falls under the knife and a stronger signal remains, then this will be a rough model of audio signal compression. … Consequently, the level of data compression will depend on how many parts (samples) the original file will be divided into and how many weak signals from each individual sample will be removed (what the bit rate will be: the number of bits in a sample of a specified duration).

The first versions of codecs for data compression acted quite crudely: they just cut off a weak signal and did not take into account the type of music, therefore, rather energetic music, without special nuances, in a compressed form does not it sounded worse than the original, whereas more complex classical and acoustic music simply lost all color and depth.

As a result of this, a transition to a more intelligent compression algorithm, with a variable bit rate, was made. Depending on the musical texture, that is, the ratio of weak and strong signals, the codec changes the amount of weak signals cut, so that we hear a more believable sound.

Obviously, with a higher sample rate (sampling) of 44.1-48.0 KHz and a higher bit rate (160-192 Kbps), we will get a sound more consistent with the original than with a sample rate 22 KHz and 64 Kbps bit rate. However, the size of the final compressed file is directly proportional to the selected sample rate and bit rate, and this is what people who distribute music in the form of compressed (compressed).

It should also be remembered that most algorithms cut the upper part of the audible range as well, starting at around 15 kHz.

There are currently several original compression algorithms, most of which are compatible with Linux.

Ogg Vorbis
Ogg Vorbis is a completely open audio format that allows you to store and transmit audio information with high sound quality (44.1-48.0 kHz sample rate, 16+ bits, polyphony (multi-channel audio)) and bit rates ranging from 16 to 512 kbps per channel. The number of channels processed can be as high as 255. This allows Vorbis to be on par with MPEG-4 (AAC and TwinVQ), WMA and PAC audio, and clearly superior to MPEG-1 Layer 3 (MP3) audio. .

Ogg Vorbis is also a streaming format, allowing it to be used, for example, for Internet broadcasts, especially since this format is compatible with Icecast. The characteristics of the codec algorithm allow you to get the final file smaller than MP3 files of similar quality.

For the reproduction the console program ogg123 is used, to encode – oggenc; both have graphic housings. More details on both are in the following sections.

MP3
MP3 or MPEG-1 audio layer 3 is by far the most popular format for storing and transmitting compressed data. This format was developed by the Frauenhofer Institut, Germany. However, despite the ubiquity of the format, it should not be forgotten that the patent for MP3 encoding and decoding algorithms belongs to a single company, so the end user at any time may find themselves in a very disadvantageous environment, such as It has already happened with the developers of free MP3 data compression tools …. You can get details about the license conditions on the developers website.

WMA
The WMA format is a proprietary product of Microsoft. It failed to occupy a market segment comparable to MP3, but it has some popularity despite serious security concerns identified. At the moment, only the universal MPlayer player can play WMA files. There are no free data compression tools for this algorithm and its appearance is unlikely.

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Main parameters to guarantee the audio quality of your digital product

Discover the main parameters to guarantee the audio quality of your digital product

Do you know the differences that exist between the formats? Do you understand how the compression rate works?

Audio settings for recorders or sound interfaces can be very confusing. But, if you are going to work with videos or podcasts, it will be useful to know how to interpret the parameters when recording and exporting files, either in Audacity (free), Reaper, Adobe Audition or in video editors.

Here we are going to talk about the differences between sampling rates (sample rate), resolution (bit depth), file compression rates and format variations. Thus, you will be more sure of the options you have regarding audio quality and you can guarantee good results.

In short, you will understand why we recommend recording in uncompressed format (WAV, for example) in 24 bits and 48 kHz. In addition, you will also know why, in most cases, we do not need more than a 192 kbps MP3 to export excellent quality audio.

We will also talk about the possibility of compressing more podcast files, which can be generated in MP3 64 kbps, mono, to facilitate online consumption.

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 It is your codec.

For example, a file in the MP3 format has * .mp3 extension and MPEG-1 Audio Layer III codec.

Examples of audio file extensions

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.

That 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 one 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 software that executes 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: without compression or compressed.

Files without compression

Audio recording equipment usually offers us options to record files without losing any information. These files, not compressed, 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 intended 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 high quality assurance).
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 in the editing stage. Because they contain a lot of information, they support more extreme alterations without harming the audio quality.

With plugins, conversions and processing, they can be handled more freely, guaranteeing excellent quality, even if a compressed file is subsequently generated.

Compressed files

Most of the equipment available in the market (cameras, cell phones and even audio recorders) usually delivers already compressed files. This type of file is more practical, easy to process, requires less storage space and has very small sizes (in bytes).

Some examples of these formats are: 3GP, AAC, M4A, OGG, WMA and MP3, which is, without a doubt, the best known. The files are like JPEG or GIF in the field of images.

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 noticeable changes in audio quality.