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lossless sound quality

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lossless sound quality

The principle of these audio compression methods is to keep as much as possible the parts that are easy to hear for the human ear.

In the main constant bit rate (CBR) mode, audible data in the audio is removed and it is easier for the human ear to hear. The more information that is retained for the part, the less information that is retained for the less audible part. As sound complexity increases, the degree of sound quality degradation becomes more apparent. For example, when listening to pure human music voice performances and performances combined with background music, pure The degree of degradation of the compressed music of the human voice is less obvious than that of the original file.

As for the lossless sound quality provided by today’s streaming platform, there are many formats, but strictly speaking, these formats, including flac and ALAC, belong to lossless compression (non-destructive data compression) rather than quality. lossless sound in a narrow sense, but due to its performance it is almost the same as WAVE, but the file is small, the decoding speed is fast, and it can be used in streaming services, so it is also a representative format of lossless sound quality that has entered the era without CD support, and it is also the current music streaming service.

Also, MQA like Tidal is a more controversial format, because although MQA is lossless audio compression in a broad sense, it focuses on driving high-quality music files that are above CD quality at a size similar to those of CD quality flac files. , but it can also be restored to the original high-quality audio format, but the controversial point is whether the higher compression ratio can maintain the same real auditory sense as the original high-quality audio has always been controversial. At the same time, MQA requires a specific device to perform hardware decoding. Yes, many devices can only decode MQA through software.

▲Currently called Hi-Res Audio generally refers to sound quality higher than that of a CD, but to be certified, the device must support the processing capability of the 24-bit 96kHz format.

However, since MP3 and AAC are previously planned destructive music compression formats, their purpose is to compress CD-level sound quality into smaller files, so most encoding specifications are presented in one presentation. CD-level 16-bit 44.1 kHz or 16-bit 48 kHz; but MQA is a format with a small file size that locks in high sound quality requirements. Basically, the MQA format will be music equivalent to 24-bit PCM or higher.

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lossless sound quality

Although lossless sound quality and high-quality streaming services have appeared on the market for a while

Like Apple isn’t the first to make true wireless earbuds, but it has ridden the wave of the market, with Apple’s launch of so-called hi-fi. compressed sound quality in Apple Music. In fact, after the lossless compression commonly known in the audio industry, lossless sound quality and high sound quality have instantly become a hot topic for many people to discuss, but whether the benefits of quality Lossless sound systems are really Obviously, the author will devote some space from theoretical concepts to practical levels. The difference is a simple overview, but the following arguments focus on easy understanding, so some of the descriptions are not entirely accurate.

What is lossless sound quality? What is the sound quality of the music we usually listen to?
The photo mentions * Introduction to KKBOX sound quality (including format), release year, sound quality, including numbers, KKBox, streaming media, Hi-Res Audio and Hi-Fi

▲ Both AAC and MP3 are destructive compression, while FLAC and ALAC are lossless compression

Before we get into the details, let’s talk about what is called lossless sound quality; From the author’s concept and cognition, the so-called lossless sound quality is a relative word rather than an absolute word. The main source is the relative word born due to the appearance of the MP3 music compression format; after the music industry went digital, digital music files were generally recorded via PCM encoding, and WAVE files were generally used on CDs. The time and space situation that MP3 was born into was because hard drive capacity was generally small at the time. To store a large amount of music data in storage space, you probably need to compress the files.

The reason why MP3 cannot be called a lossless format is because it essentially compresses the original WAVE in a way that limits the bitrate by combining concepts like the psychology of sound. The bitrate compression mode, compared to the bitrate of the original WAVE file, compresses at least in a range of 1:4 to 12:1. The higher the bitrate, the greater the amount of retained information. For example, AAC format also adopts similar audio psychology for compression, but the efficiency is better than MP3. Therefore, most of the lossless sound quality of most streaming platforms currently uses AAC as the mainstream.

About Lossy

About Lossy

Lossy

We all love good music. More recently, the audio CD was good digital music. This is 44100 Hz, stereo, 16 bits (linear) per channel, not compressed in any way, which means, according to Wikipedia, 1411.2 kbps.

Lossy

But at the end of the 20th century, in the era of the birth of multimedia, when music began to be played not only on players, but also on computers, it turned out that the audio CD (that is, naked PCM) is even better. . compress. There was, for example, Microsoft ADPCM, which compressed this case a bit, without losing quality, in WAV files. But generally speaking, the original 44 kHz stereo would still require a lot of space this way. Hence, the quality dropped to 22 kHz mono. One of the first multimedia albums of that time: “Immersion” from the group “Nautilus Pompilius”, is still around, and I did.

So MP3 won. To store and distribute compressed music. At 128 kbps “CD Quality”.

MP3 came up strangely. Technically, this is MPEG-1 Audio Layer 3. A layer for compressing audio data into a modern, progressive standard for storing video data on Video CDs. Just packed in its own .mp3 file format. The video CD is no longer interesting to anyone. The following MPEG-2 standard is used in DVD and digital television broadcasts (not HD). And the next MPEG-4 standard is now used for HD video and continues to evolve.

MP3 was revolutionary. It was (almost) the first lossy compression format. When we don’t try to preserve everything that was in the original signal, but, based on some psychoacoustic model, we cut out what a person is not going to hear anyway, and compress the rest. Like JPEG.

Then I tried digitizing the accumulated audio collection. Compact cassettes (just “cassettes”, but more correctly “compact cassettes”) turned out to be complete shit. The frequency range is such that it makes no sense to sample with more than 22 kHz. There were no reel-to-reel recorders in the house. But vinyl records shook the sound quality. With good equipment, you can draw better quality than a CD. You just need to get rid of the clicks.

And then I realized that MP3 is shit too. At these same 128 kbps, the sound quality suffers greatly. And the scariest thing is that vile metallic hues appear where they shouldn’t be. My ears need at least 192 kbps, and the more the better.

Let’s take a hint from a famous punk rock band in the past. Like FLAC. It is such a modern lossless compression standard that it has successfully replaced WAV. Because it is free.

The original is CD quality, so frequencies up to 22 kHz are present as expected.

Original flac

We are going to harvest with FFmpeg, or rather with LAME.

At 320 kbps and 256 kbps, the spectrogram looks almost like the original.

At 192 kbps, there are signs of a 16 kHz cutoff. The spectrogram “darkens”, apparently, the psychoacoustic model has cut something out. By ear, the higher frequency “bursts” really disappeared.

MP3 192 kbps

At the notorious 128 kbit / s, everything is already specifically cut off at 16 kHz. Background sounds are “fuzzy” and begin to bubble. Nothing to do with the original in terms of enjoying the musical details.

MP3 128 kbps

But you can do 64 kbps in MP3. The stereo is gone. Everything gurgles terribly and irritates with completely strange sounds.

Data compression: lossless or lossy

To be able to store large amounts of data, a huge amount of storage space is required. When the space is at some point full, a new storage space is usually made available. Mainly in the form of new hard drives, server systems or the like. But there is another way to store more data: data compression.

Lossless vs Lossy

Data compression works like a pillow you squeeze
Figuratively speaking, data compression works the same way as when you squeeze a pillow. Not all air is required between the pillowcase and the feathers. By squeezing the pillow, you compress it by removing the air (as much as you can); the pillow becomes smaller, that is, more compressed than before.

It is similar with data compression. Here also items that are not absolutely necessary, in this case data, are removed and the storage space still required by the remaining data is reduced.

Lossy vs Lossless Compression

Different lossless compression encoding methods.

When it comes to data compression, a distinction is made between lossless compression and lossy compression, so it can be further subdivided into different types of compression.
Lossless compression is generally only done with text files. If the text is saved as a character string and not as an image or the like, the storage space can be saved using the dictionary method, for example. Recurring parts of the string are simply replaced by abbreviations.

Text: Hello world. Hello user
Encoding: world X5. X5 users.

With the help of Run Length Encoding (RLE), identical text components that are placed one after the other are only saved once. This can also save storage space.

Text: Today was beautiful, beautiful, beautiful and tomorrow will be more beautiful.
Coding: Today was / 3 / beautiful, / and tomorrow will be more beautiful.

In entropy encoding, as is the case with Huffman code or arithmetic encoding, for example, text elements are sorted in binary and encoded according to their frequency, and the most frequently occurring element is given the binary number smaller.

With these numbers, the text elements are stored in a separate dictionary.

Text: IF YOU FLY BACK, FLY, FLY, FLY, FLY AFTER.
Coding: 10100 1 1 1101 1 1 1 11

Difference between lossless and lossy compression

The benefit of lossless encoding is clear: it ensures that all “compressed” data in the compressed data packet can be accessed and restored.

In addition to lossless compression, there is also lossy compression. Irrelevant information is not encoded here, but is directly removed. Therefore, we speak of a reduction in irrelevance.

Lossy compression: the MP3 format

Of course, this procedure can lead to extremely high compression rates. However, this irrelevant information is irrevocably deleted. This means that the original state cannot be restored after compression.

Lossy compressions are often used for image, audio, and video files, as they often have to handle large volumes. The MP3 format is a classic example in this context. Here, frequency patterns are removed from an audio file that are almost inaudible to the human ear. This saves storage space.

If you compress data packets, you can use your own data storage capacity better than uncompressed data packets. However, you should always consider the type of compression you are using. Because lossy compression is not always desirable.

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.

Files without compression, lossless and lossy formats

Files without compression, with compression but without loss and with compression and with loss … what does that mean?

There is currently a huge confusion in most people about audio formats and that is why we are going to give an explanation that is as simple and clear as possible so that most of the people who read can understand enough to be able to make decisions about it. .

We will not try to get into technicalities or knowledge What are for specialists or connoisseurs or programmers, such as those who developed the mp4gain, but rather we will talk about general concepts at the beginner level but that can allow a correct understanding of the matter.

So the first thing we must understand is that the quality of an audio file depends on the amount of details it contains and for it to contain many details, it takes up a lot of space on the hard disk.

We could say that there are three groups of audio file formats:

– audio formats that do not have compression such as WAV, AIFF, etc.

– formats that compress audio but do not have a loss of information. FLAC, MPEG-4 SSL, WAV PACK, etc.

– There are also the formats that the audio compresses but that do have a loss of information, for example MP3, Ogg, HERE, ETCÉTERA

Now let’s clarify what it means that some formats do have compression but do not have loss of information while others also have compression but do have loss of information.

The formats that are compressed but have no loss of information what they do is something very similar to zip the file. In other words, they simply compress.

The original information but they do not discard anything, therefore when unzipping the file the original file is obtained again that had all the details and therefore is of very high quality.

On the other hand there are files such as MP3 that are compressed but also to achieve greater compression what they do is that they get rid of some part of the information. For example, those frequencies that are not audible to the human ear also get rid of that information that is redundant and they also use the method called masking which part of the idea that a sound that is very loud and is very forward It will be able to mask other sounds and the human brain will not perceive those other sounds. Therefore, according to this theory, they can get rid of these sounds that have been masked and the file will sound more or less the same to the human ear.

This concept of sound masking was one of the great milestones that made MP3 become so popular because it could compress files a lot, at a time when disk space was not superfluous, and yet they sounded pretty good to that ear. era and those people.

Also the programs that made the normalization of the audio volume, achieved results that at that time sounded good, but at this time the listening ear as a has become much more demanding and sophisticated. And so we need much more modern normalizers with much more algorithms. more powerful like mp4gain.