The different audio file formats

Les différents formats de fichier audio

The evolution of technology has transformed the way we consume music. Many audio file formats have emerged, but it is not always easy to understand their differences. Here we will talk about the most common ones.

Analog - digital conversion

First of all, we must remember the difference between analog and digital audio.

Before the arrival of digital technology, we recorded music on tapes and burned the sound on vinyl, these processes are analog.

Digital audio uses computer code, so it was necessary to find a way to translate the (analog) sound wave into a signal understandable by computer devices, i.e. a signal made of 0s and 1s (digital ). To do this, we use an analog/digital converter which will cut the sound wave into small pieces called samples .

Analog signal vs digital signal

Sampling frequency

Sampling consists of retranscribing, at regular intervals, the value of a signal. The sampling frequency is the number of samples per unit of time and is expressed in hertz.

The higher the sampling frequency, the better the resulting digital signal is.

Continuous signal vs sampled signal

The CD standard is 44,100 Hz , which means that for every second, there are 44,100 samples. This sampling frequency was chosen for two main reasons.

The first reason is that the human ear can only perceive sounds within the 20 Hz - 20,000 Hz spectrum. To avoid losses when digitizing sound, the sampling frequency must be at least twice as high as the maximum frequency of the sound to convert, i.e. minimum 40,000 Hz.

This is why the 44,100 Hz resolution is the standard, it covers the entire range of frequencies audible to the human ear and even a little more. This means that if you export music with a sample rate higher than 44,100 Hz, your ear theoretically won't be able to hear the difference.

The second reason is the storage capacity constraint of CDs. With this resolution a CD can contain 80 minutes of music, a doubling of this sampling would have halved this capacity.

The main audio formats

Audio files can be placed into 3 different categories: lossy compressed, lossless compressed and uncompressed .

Audio compression aims to reduce the amount of data , to store music more easily . The compression can be more or less important, it is this which determines the value of the bitrate , that is to say the flow of information per second, it can be between 32 kbps and more than 1000 kbps.

Lossy compressed formats

Logos lossy compressed file formats: MP3, AAC, WMA and Ogg

The majority of lossy compression algorithms use the particularities of human hearing to remove data that they consider to be “least important”, such as frequencies that the human ear cannot perceive or at least very with difficulty. These algorithms are destructive , details are completely removed to reduce file size. Depending on the intensity of the compression, the audio quality may be significantly degraded .

  • MP3 (MPEG-1 Audio Layer III or MPEG-2 AUdio Layer III)

The MP3 format is a strong compression format, its quality is lower compared to other formats but it has the advantage of being able to be stored easily since it takes up little space in addition to being compatible with all devices. Its bit rate can be between 32 and 320 kbps.

  • AAC (Advanced Audio Coding)

This format offers an excellent compromise between compression rate and sound quality, very close to that of a CD. ACC requires a paid license for manufacturers, making this format less universal than MP3.

  • WMA (Windows Media Audio)

This format has compression substantially identical to MP3 with the difference that WMA retains certain high frequencies. It natively supports rights management systems (DRM), which makes it possible to verify the legality of the download.

  • Ogg

Ogg is an open source format, it has higher quality than ACC for an equivalent bit rate. It owes its differences to its packet-processed compression structure.

Its bit rate can go up to 500 kbps although at 256 kbps its quality level is close to CD.

Lossless compressed formats

Logos lossless compressed file formats: FLAC and ALAC

Lossless formats compress data without destroying it , it is simply reorganized so that it takes up less space. When read, the data is decompressed and returned to its original state. These are the formats that are offered by HI-FI streaming platforms such as Qobuz, Tidal or Apple Music.

  • FLAC (Free Lossless Audio Codec)

This format is open source, its audio quality is much superior to other formats while offering a limited file size with a bit rate that can exceed 1000 kbps.

This is the most common high definition format, the majority of devices are now capable of supporting it. However, it requires much more storage space than lossy formats.

  • ALAC (Apple Lossless Audio Codec)

ALAC is Apple's version of FLAC, so it is only compatible with Apple devices. It is criticized for being a little less efficient with a compression of 40% to 50% (compared to 60% to 70% for FLAC)

Uncompressed formats

Logos uncompressed file formats: WAV, AIFF and DSD

Uncompressed formats do not apply any processing , the analog waves are converted into digital format and it is this same format which is contained in the files. The disadvantage is that they can be very large and therefore difficult to store and they require a much longer download time than a lossless compressed file for example.

  • WAV (Waveform Audio File Format)

WAV is not a format strictly speaking but a container of different formats (PCM most of the time). WAV is flexible, it allows you to choose whether or not to apply compression, it is a very high quality format but not suitable for listening on a smartphone due to the size of the files.

  • AIFF (Audio Interchange File Format)

AIFF is an Apple version of WAV, so it is only compatible with Apple devices. Unlike WAV, AIFF supports metadata management.

  • DSD (Direct Stream Digital)

DSD is a fairly rare file format despite its performance. For many audiophiles, DSD is the format par excellence. It is differentiated by its conversion method called Delta Sigma.

Octavio Stream network player

Octavio Stream is a WI-FI network player that allows you to stream music from streaming services (Qobuz, Tidal, Deezer, Spotify and Apple Music) to Hi-Fi audio systems. The Octavio Stream has a Burr DAC Brown PCM5102A which supports the majority of formats such as MP3, OGG, WMA, APE, ALAC and FLAC and which supports resolutions up to 24 bits/192 kHz.

By using our Octavio Virtuose application to stream the FLAC formats available from Qobuz on your Octavio Stream , you are assured of no loss of sound quality and of being able to take full advantage of Hi-Res.

In conclusion, there are many different audio file formats that cater to different uses. The key is to find the balance between sound quality and practicality of storage and playback. It's also worth considering the devices you're streaming your music to.

Today, with storage constraints decreasing and throughput increasing, better quality file formats are likely to become more widely available.

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