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Lossy Audio File Types: How It Is Different From Lossless

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Lossy Audio File Types: How It Is Different From Lossless

Lossy Compression vs Lossless Compression

Lossy is a word used in digital audio to describe the type of compression used to store audio data. The algorithm used in the lossy audio format compresses the audio data in such a way that it discards certain information. This loss of signal means that the encoded sound is not identical to the original.

lossy vs lossless

Lossy audio produces lower quality audio and has a smaller file size.

Lossy compression is also called irreversible compression because data that has been deleted is impossible to recover.

What is the difference between Lossy and Lossless?
When you create MP3 files by ripping one of your music CDs, some details of the original recording are lost, making it a lossy format. This type of compression isn’t just limited to audio; for example, JPEG image files are also lossy compressed.

Sheets of colored paper compressed into a ball

This method is the opposite of lossless audio compression used for formats like FLAC, ALAC, and others. In this case, the audio is compressed in such a way that the data is not deleted. The sound is identical to the original source.

Lossy archives take priority when it comes to compatibility. While lossless files are only supported by some devices and apps, a lossy audio format like MP3 will work on almost any device.

How Lossy Audio Compression Works
Lossy compression makes certain assumptions about frequencies that the human ear is unlikely to detect.

When a song is converted to a lossy audio format such as AAC, the algorithm analyzes all frequencies and then discards the frequencies that the ear should not be able to detect. These low frequencies are filtered or converted into mono signals that take up less disk space.

Another technique eliminates very quiet sounds that the listener is unlikely to notice, especially in the loudest part of the song. This approach reduces the size of the audio file while maintaining the highest possible audio quality.

What happens to the audio when it is compressed?
Lossy compression introduces artifacts. These artifacts are unwanted sounds that are not in the original recording but are a by-product of compression. This noise degrades sound quality and is noticeable when music files are converted using low bit rates.

Various types of artifacts affect the quality of the recording. Distortion is one of the most common artifacts. For example, distortion makes the drums feel weak, without any real beat. Song voices can also be affected, resulting in harsh vocals and lack of detail.

In many cases, casual listeners can’t tell the difference between lossy and lossless encoding, although some audiophiles using very expensive equipment claim to hear the difference. The difference in quality is only noticeable when very low data rates or aggressive compression algorithms come into play.

Why compress audio files?
Most digital audio formats use some form of compression to efficiently store sound. Without compression, the file sizes would be very large.

For example, a typical 3-minute song stored as an MP3 file is between 4MB and 5MB. Using the WAV format to store the same song, but without compression, results in a file size of approximately 30MB, at least six times that size. Fewer songs fit on your smartphone or hard drive when you choose uncompressed audio formats

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Uncompressed and compressed formats

Popular audio formats

Uncompressed formats

There are audio formats that do not have compression and are the best in terms of sound quality. On the other hand, they take up much more memory space and a lower transmission speed than compressed formats. With professional software such as Pro Tools, SuperCollider or Max, you generally work with files of this type. The two main formats are:

WAV (wave). Audio format developed by Microsoft and IBM for compatible IBM PCs. In this format, musical instruments feel the same regardless of the PC on which the file is played (with the same acoustic quality of the hardware components, of course).

AIFF (Audio Interchange File Format). The format developed by Apple is also called the Apple Interchange File Format.

Audio formats

Lossy compression

It allows for more compression, but at the expense of sound quality. Lossy compression methods generally tend to discard information considered useless, keeping only the essential ones and arise from the idea that not all frequencies contained in a sound spectrum are perceived by the human ear. Then the high frequencies are cut off, which are believed to be the least distinct in our hearing. Obviously, the more frequencies you cut, the more the space occupied by the audio track decreases and with this also the quality of the result as a reconversion process. It does not allow the complete restoration of the cut-off frequencies. Let’s see what are the main audio formats of this type:

MP3 (MPEG-1/2 Audio Layer 3). Audio compression algorithm capable of drastically reducing the amount of data required to reproduce a sound, compromising obtaining an almost faithful reproduction of the original uncompressed file. The best codec for compression is Lame. maximum achievable bit rate 320 Kbps.

WMA (Windows Media Audio). Audio file standard invented by Microsoft. Audio compression format very similar to an MP3.

OGG (Vorbis). It is an open source algorithm and with the same perceived quality, it allows greater compression than the MP3 format, obtained through advanced psychoacoustic research.

AAC (advanced audio coding). It is an audio compression format officially included in MPEG-4. Provides superior audio quality to MP3 format with more compact encoding. Currently it is used mainly by Apple, which in the variant that manages copyright has a compression of 128 Kbps (the standard of the iTunes Store) and corresponds to that of an MP3 at 192 Kbps at constant bitrate. Conversion times are a bit slower than other formats.

AC3 (Dolby Digital). Dolby Digital is a multi-channel audio coding system developed by Dolby Laboratories Inc and used in film, digital TV, laser discs, DVDs, and other digital audio streaming or playback media. It works from a minimum of 96 kbps to a maximum of 640 kbps. In cinema, Dolby Digital is used with only 320 kbps of bandwidth, as it prints in the limited space available between the slide holes of the films. Generally, in DVD it is used with a bit rate of 192 kbps to encode stereo signals (2.0, 2.1) or stereo surrounds, and with a bit rate between 384 and 448 kbps for 5.1 signals.

Lossless compression

These compression methods try to reduce the space occupied by the track without going to touch the sound. The compression rate is much lower than with lossy methods, but there is no loss of quality and the sound is identical to the original when converting. Let’s see what are the main audio formats of this type:

FLAC (Free Lossless Audio Codec). The widespread open source audio codec is currently well supported by various audio software. Unlike most lossless compression algorithms (like ZIP and gzip, for example) that only achieve 10-20% compression, it achieves significant compressions, on the order of 30-50%.

APE (Monkey’s Audio). No lossy format that allows us to reduce the space our music occupies by approximately 50% (in some cases even more). Currently it is no longer developed.

ALAC (AApple Lossless Audio Codec). The format developed by Apple stores data in an MPEG-4 container with the extension .m4a. It does not have Digital Rights Management (DRM) and is now deprecated.

Music quality of files (lossless and lossy)

Music files can be the product of the perfect extraction of the music contained in CDs, called bit by bit. With this phrase we immediately clear the field of feeding unjustified prejudices towards the archives. The files are not of the same quality as CDs when using lossy formats: MP3, AAC, M4A. Besides these, there are formats that do not use any type of compression: WAV and AIF, which are the exact copy of the songs stored on CDs or even the original master recording format used to create CDs. Or there are formats that even using compression are “lossless”, called lossless: the most widespread of them is the FLAC format, not surprisingly adopted as a standard in the distribution of content in CD quality or higher. The FLAC format uses a type of compression that does not remove the original data. When unzipped, FLAC files have exactly the same bits that were present before compression.

Lossy - Lossless

Before there are misunderstandings about the relationship between lossy and lossless files, we specified that if you have an MP3 file and convert it to FLAC, the data removed from MP3 transformation will not magically appear again. No conversion can regenerate the lost data into a lossy file. You can convert FLAC files to WAV or AIF because the compression used was lossless.

Lossy and lOOSLESS

The FLAC format also has advantages over WAV and AIF, the applied compression reduces its size and saves storage space and data bandwidth in reception / transmission when transmitting over the network. Besides this function, FLAC has another advantage over WAV, the information describing the tracks and the cover image can be inserted into the files. The information inserted in the files is called TAGs, the FLAC format provides for the insertion of this information that software applications and APPs read to recognize the content of the audio tracks. This simplifies the management of music collections, which without TAGs would present indistinguishable lists of audio files. Unfortunately, the standard WAV format does not allow the inclusion of TAGS in files.

Let’s continue the discussion on the playback chain of a portable Hi-Fi system. The technical quality of the content to be reproduced affects the final quality of the reproduction.

After adopting quality headphones, it would be wise to switch to lossless audio formats, to at least benefit from the original quality found on CDs.

Lossless music

Most of the sites that sell music online offer it in lossy formats, so the problem is how to get music without loss. Anyone with a CD can start by ripping them. Ripping is the term used to describe the transformation of the tracks contained in a CD into files. Anyone who wants to delve into the subject can read the writings dedicated to Ripping and the creation and management of music collections: What software for ripping and Creation and management of music files luquida.

In addition to CD ripping, there are websites that sell lossless music online in CD quality and Master Quality (Hi-Res), the latter is superior to CD and in many cases coincides with the original recording made in the Recording Studio.

High Resolution Music (HRA) has higher technical specifications than expected for CDs. Resolution ranges from 16 bit to 20/24 bit and sampling from 44.1 kHz to 48 / 88.2 / 96 / 176.4 / 192 kHz. For a description of the processes and characteristics of digitization, read the following text: The digitization of sound. With respect to these specifications we believe that the determining factor is the 24-bit resolution combined with sampling performed at least at 48 kHz.

Speaking of MP3 files, we usually refer to the bit rate, which with this format does not exceed 320 Kbps. The bit rate indicates the bits per second transmitted in a music stream. It is quite evident that a music stream consisting of more bits will contain more audio data. To orient yourself between these parameters, it is good to bear in mind that an uncompressed CD quality audio stream (16 bit 44.1 kHz) is 1,411 Kbps, converted to FLAC the stream will decrease between 30 and 50% of the format’s bit rate. uncompressed. Therefore, the CD quality stream generated by a FLAC will vary approximately between 705 and 988 Kbps. Obviously for high resolution formats the data stream will be proportionally higher depending on the specifications offered by the individual files.

The technical quality of the content to be reproduced as well as the reproduction devices are essential complements to obtain the best sound result.

Data compression: lossless and lossy

In computer science and telecommunications, the term data compression (data compression) will indicate the data processing techniques that allow the reduction of the quantity of bits necessary for the representation of the information in digital form. In practice, for example, data compression makes it possible to reduce the number of bits required for the transmission of a video transmission, allowing it to be viewed on the Internet even in the presence of a connection that is not fast enough.

For files, data compression allows you to reduce the size (number of bits) of the file – this is advantageous because it reduces the space occupied by the file on disk and allows you to transfer the file more quickly (for example, by email).

Compression techniques fall into two main categories:

lossless compression (lossless):

in this case it is possible to rebuild the file from the compressed without loss of information;

lossy compression (loss)

compression occurs to the detriment of information quality, for example, through loss of image definition or sound quality of an audio file; in this case it is not possible to rebuild the file from the compressed file before compression.

The two techniques are used in different areas. As already mentioned, lossy compression is often applied to images, sounds and videos as it enables significant reductions to be made from the original data, at the price of an often negligible loss in quality. In addition, lossy techniques can be applied during data transmission (runtime), that is, it is not necessary to know all the data to be compressed to apply them: this is obviously an advantage in the transmission of transmissions over the Internet . Among the best known lossless algorithms, we mention jpeg for images and mp3 for audio and mpeg for videos.

In contrast, lossless compression is used when you want to compress text documents, programs, databases, circuit diagrams, etc. and in any case where the loss of the original data is not accepted. The lossless compression category includes .zip and .rar formats, often used to compress files and file folders.

Later we will discuss lossy compression techniques, talking about multimedia formats. Here, instead, we want to deepen the understanding of lossless compression.

Lossless compression algorithms

Lossless compression techniques (algorithms) can be divided into two main categories:

statistical compression;

replacement compression

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Statistical compression is based on the input study to be compressed. Statistical studies are carried out on the input format to obtain a good compression. For example, in a text file to compress, the relative frequency of each character is studied and then the shortest code is associated with the character present several times in the text; vice versa, characters present with low frequency are associated with a longer code. Codes like Huffman’s are part of this class, which we will discuss in the next lesson.

As for substitution compression, this is based on the idea of replacing, in a file, all occurrences of repeated strings with pointers to previous copies of the same string. Compression is due to the fact that the length of a pointer is usually less than the length of the string being replaced. As a result, the higher the repetitions of string occurrences in the file to be compressed, the greater the degree of compression achieved.