Comparison of audio formats

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What is the best audio format for what purpose?

Comparison of audio formats

All radio and podcast producers are faced with the question: What audio format is best for my shows and contributions? There is usually no simple answer. Each file format and each codec has advantages and disadvantages.

Audio Formats Comparison

Before converting / converting, you need to be clear about what you plan to do with your audio file: Should it be published to the NRWision media library? Is the program designed to broadcast on the Internet or for the home audio system? Should the file be edited again if necessary? Only then can you weigh which audio format and which properties make the most sense.

Audio File Formats comparision

Compress without loss?

You must decide whether you want the best possible sound quality or the smallest possible file size. With some audio codecs, sound is retained at its full bandwidth and without loss. Other codecs compress the file so that it takes up less space or is faster to transfer online. At best, it can still be played on many different devices and players. Depending on the strength of the compression, the sound of music or voice recording may also be audibly affected.

In the case of audio files, information such as sample rate and bit rate always play a role.

The sample rate indicates how often the level is saved per second. CDs, for example, have a sample rate of 44,100 Hz. 44,100 values are stored for one second of music.

Bit transfer rate

Bit rate defines the amount of data that is processed per second. It can be constant or variable and therefore also influences the sound quality.
Important: When converting audio files to other formats, the quality cannot be improved, it only deteriorates or is preserved. With each compression, some of the audio data is lost, although it is not necessarily audible.

Next we present the audio formats and their properties.

MP3

File extension: .mp3

MP3 is probably the most popular and widely used audio format in the world. It became the standard for music files on the Internet more than 20 years ago and has been freely available since 2017. By the way, MP3 was developed by the Fraunhofer Institute in Germany, among others. Raw audio is highly compressed when converted to MP3 files to save storage space. Only what humans can hear should be preserved. You can set the degree of compression, the so-called bit rate. 192 kBit / s (kilobits per second) roughly corresponds to CD quality. At higher bit rates, MP3 files sound lossless to most people. Lower bit rates are used, for example, in Internet radios.

Advantage:
widely used, compatible with many playback devices, high compression

Disadvantage:
possibly loss of audible quality, especially at low bit rates

Wav

File extension: .wav

WAV files are not compressed and therefore take up a lot of storage space. But they can be used well for audio editing and can be easily edited in almost any software.

WAV files were developed for Windows computers in 1991. However, they can also be reproduced and used on other operating systems.

Advantage:
no need to encode / decode when editing

Disadvantage:
very large files

WMA

File extension: .wma

Originally, the WMA (Windows Media Audio) format was supposed to compete with MP3, but it could not be established equally. Audio data is also compressed here, if possible without audible loss.

Some versions of WMA files may contain a certificate key to prevent piracy.

Advantage:
good compression with high sound quality

Disadvantages:
not very widespread, only supported by a few players

AAC (advanced audio coding)

File extension: .aac

This audio format is considered the successor to the MP3 format. With the AAC format, developers have managed to further reduce memory size while maintaining the best possible sound quality.

The AAC process is being used with increasing frequency on music websites, Internet radio stations, and as a soundtrack format for video files.

Advantage:
very good compression, small files with high audio quality

Disadvantage:
not yet compatible with all programs and devices

Ogg

File extension: .ogg

In Ogg files, there is actually a container format. In addition to compressed audio, it can also contain video and text data. Also, Ogg files can be used well as an online stream. Even so, the format never prevailed against MP3 among home users.

Advantage:
small file size with good sound quality, no license

Disadvantage:
not compatible with many programs, must be converted for audio processing

FLAC (Free Lossless Audio Codec)

File extension: .flac

The name already gives it away: the FLAC codec is freely available and compresses audio files without loss of quality. The format is mainly used for music that can be faithfully reproduced thanks to FLAC. More and more players support FLAC files, sometimes just with the help of a plugin.

The FLAC codec makes audio files 30 to 60 percent smaller. This makes them much larger than MP3 files. To do this, you can decode it and thus restore the original data without loss.

Advantage:
no loss, no license

Disadvantage:
relatively large files, not natively supported by all players

Opus

File extension: .opus

The latest file format from our overview should become the Internet audio standard. Opus is developed openly and has several advantages. The audio codec significantly reduces the bit rate again. The quality of music and language is preserved as best as possible. Additionally, Opus files can be streamed and contain metadata.

Opus plays practically no role (yet) in audio processing. We are curious to see if and how the format will prevail for years to come.

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Audio formats

Before you know the audio formats, know that they are divided into two main groups: the compressed and the uncompressed.

Uncompressed formats are those in which the audio quality is assessed and without loss of information, which guarantees that the audios are practically identical to the real ones. Tablets reduce the original file size, taking up less space on your computer or cell phone memory. However, the quality and information may be compromised.

It is worth mentioning that it is not just a good format that guarantees that the end result will be of excellent sound quality. You need to do your part, too, using good audio software to make the necessary changes and “cleanup,” as well as using quality equipment to record your voice.

1. Advanced Audio Coding (AAC)

It is considered the main competitor to the most famous format on the Internet, MP3, and is commonly used on Apple devices, based on the MPEG-4 standard.

Compared to MP3, AAC has more flexibility, which means you will experience less data loss and quality when compressed. Also, it has a better level at lower bit rates, such as 128 kbps.

2. OGG Vorbis

This is a non-proprietary format, that is, they have no restrictions for audio players to play it. Also, it has a better compression rate than MP3, however it is not as well known or advertised.

It is widely used in game audio, because among other qualities, it brings open source, which provides greater customization, but is difficult to standardize. Its audio quality is quite satisfactory.

3. MP3

Considered the most popular audio format in the world, MP3 offers high compatibility, allowing music and audio to be played in virtually any program or media player.

It was created in Germany and uses the so-called perceptual encoding, which encodes only the sounds that humans can hear. Of all, it manages to be the most balanced in terms of quality versus size.

It may get to lower bit rates, but there may be a final quality loss.

4. WMA

This is Microsoft’s standard format and also quite popular. Unlike MP3, WMA allows the creation of content-protected copies, thus preventing your music or other audio productions from being pirated.

Microsoft’s proposal is that the format achieve a sound property equivalent to that of MP3, but in a much smaller size. In practice, this does not happen, but at low bit rates the result is very similar.

It offers four codecs:

Standard WMA: acts as an MP3 repeater;
WMA Pro: guarantees higher definition audio;
WMA Lossless: allows file compression without loss of quality;
WMA Voice – Aimed at low bit rate voice recordings.

5. MP2

Although it already has a successor, MP2 is still widely used, being the standard format for transmitting radio and television audio. It is a file extension for MPEG -1 layer II playback (MP3 plays in MPEG -1/2 layer III).

One of the attributes of the MP2 is that it still has great compatibility, as well as fewer errors than its successor. In addition to having better performance in audios with higher bit rates.

6. Real Audio

RealNetworks proprietary format. They have multiple audio codecs and great performance for those with low bit rates. It was constantly used in dial-up modems, hi-fi formats for music and streaming, as is the case with web radio.

RealNetworks is an internet provider that works with streaming services. It was founded by a former Microsoft executive and also offers entertainment services through subscriptions.

7. Audio Coding 3 (AC3)

Created in 1983 by Dolby Laboratories, AC3 is primarily used in DVDs, Blu-ray players, home theaters, and HDTV playback. It can reproduce frequencies between 20 and 20,000 Hz, which is equivalent to the human audible sound.

Therefore, the AC3 can reproduce unique and detailed sounds, with very good quality. Its bit rate goes up to 640kpbs and its display speed goes up to 48kHz.

8. WAV

One of the best characteristics of this format is that it has a high sound fidelity rate, that is, it faithfully reproduces what was recorded without compression or loss of data.

It is widely used by those who work with audio editing, since it will be able to manipulate the real sound and without any interference. It is also considered for those who need more definition and sound fidelity as possible for their productions.

Mp3, the winner

In the era of broadband connections, fiber optics and HD videos on YouTube, MP3 remains the reference format for audio files. We are now so used to listening to music in compressed formats, and often through poor quality playback systems, that it is difficult for us to remember what listening to music really means. The recent evolution from download to hit-and-run streaming has only made the situation worse by further devaluing the value of music. When was the last time you listened to a record from start to finish without interruption, spending those 30-40 minutes on “simple” listening activity?

Premise: This post is not a crusade against Spotify because I use it myself for new releases or to have some background music at work, it is not even an analog vs. digital (or vinyl vs. CD vs. MP3) post because on this topic en Much has already been said. My goal is to make you understand what you are missing, in qualitative terms, if you listen to music in compressed formats.

Sampling and theoretical aspects.

Audio recording on a computer or digital medium assumes that the signal passes through an analog> digital (AD) converter, so that the continuous electrical signal generated by microphones or musical instruments is transformed into a digital signal (series of 0 and 1) This process is called sampling. The final quality of the recording depends on several factors: converter quality, sample rate, and bit depth.

To make an easily understandable comparison: When shooting a movie, the “analog” reality perceived by our eye is stored in a movie that takes 24 frames per second. If we consider the standard of the audio CD (44.1 kHz, 16 bits), for every second of music 44100 pictures are taken from the computer to the continuous electrical signal. If with the sampling frequency we have simply established how many times in a second the waveform will be analyzed, with the bit depth we assign to each sample a numerical value: 2 ^ 16 = 65,536 possible values.

If you wonder how it got to 44,100, I refer you to the Nyquist-Shannon sampling theorem.

When we press the record button on our computer, through the PCM (pulse code modulation) sampling process described above, the files are saved in uncompressed WAV or AIFF format.

Lossless files and lossy files

PCM files take up a lot of space on our hard drives because, as we have seen, there is the data necessary to describe the analog waveform in as much detail as possible. Indicatively, a WAV or AIFF file as audio CD will occupy 10 MB for every minute of music.

To overcome this problem, remember that in the early 2000s storage space cost around $ 10 / GB, while today the price is around $ 0.03 / GB (source): Audio formats have been introduced that , through an algorithm encodes and decodes information, reduces the size of the file. These codecs fall into two categories: formats with lossless compression and formats with lossy compression.

As the name implies, lossless compression indicates a reduction in file weight (usually around 50%) without loss of information. Leaving the world of audio aside for a second, ZIP and RAR files are clear examples of this type of compression: at any time we can “unzip” such a file and have access to the original information again without this no way has changed.

The most common file formats are: FLAC (Free Lossless Audio Codec) and ALAC (Apple Lossless Audio Codec).

Lossy compression, on the other hand, implies that some of the original audio information is somehow removed to obtain a file that weighs even 90% less than the PCM.

By what criteria is information removed without “compromising” the original audio too much? Since our hearing is an imperfect instrument, codecs exploit two principles of psychoacoustics: the minimum threshold of audibility (the human ear does not perceive all frequencies in the range between 20Hz and 20kHZ equally) and masking (a weaker sound). is masked, making it inaudible, by a louder sound.)

Compression algorithms, however advanced, introduce a number of artifacts into audio files that, if played back in discrete quality audio systems, can be easily recognized or at least noticed even by an inexperienced ear. Several studies have shown that an untrained ear does not distinguish the difference between an uncompressed file and an MP3 with a bit rate equal to 256kb / s or more.

The most common lossy formats are: MP3, OGG Vorbis, AAC.

The victory of MP3

Since its introduction in the mid-1990s, MP3 has established itself as the industry-standard consumer format fueled by file-sharing through peer-to-peer channels, where, with slow connections, the heaviest file was the one it was downloaded, the longer it took to obtain it, and since the market introduction of MP3 players in which we tried to store as much music as possible and, therefore, we resorted to very compressed files.

In the transition from the era of downloading to that of small transmission files, they ensure smoother and smoother data transmission.

Despite, therefore, the evolution that has taken place in recent years in the speed of Internet connections and the reduction in the price of storage systems, only in recent years have services been created to buy files from High-quality online audio (HD tracks) or HD streaming services (Tidal).

Examples and audio files.

The main services we use to buy or listen to music use these compression levels (all information is taken from the official websites of each service at the time this publication was written).

Spotify: OGG Vorbis files at 96 kb / s (normal mobile quality), 160 kb / s (normal desktop and web player quality, high mobile quality), 320 kb / s (premium users: high desktop quality, very high quality mobile).
iTunes: By default, CDs are imported into 128 kb / s AAC files. Files in the iTunes Store are of this quality, except for “iTunes Plus” songs converted to AAC at 256 kb / s.
Pandora: 64kb / s AAC (free users), 192kb / s AAC (premium users).
YouTube: HD videos (720 or 1080p) have an audio quality equal to 384kb / s, SD videos (360, 480p) have an audio quality equal to 128kb / s.