About modern audio encoding formats
While MP3 is still the de facto format for compressing music on the computer, there are many other lesser known compression standards. Some of them are outdated and practically unused, some have appeared recently and have not had time to occupy their niche yet. Here I will focus only on formats that use lossy compression, as they allow you to achieve the highest degree of compression of audio data.
What is lossy compression? Only the file encoded in this way and then again decoded into a wave file will be binary different from the original file (i.e. the content of the files will be different), although the difference may be subtle or completely invisible to the ear. How do you manage to achieve such a result? These questions are answered by psychoacoustics (see, for example, a selection of articles from the journal “Sound Engineer” for 1999-2000), a relatively new science that deals with the study of how the human brain perceives sound. The fact is that we do not perceive all the solid information. For example, we can hear footsteps on an asphalt road quite clearly in the absence of strange sounds, but the footsteps themselves are completely inaudible if a passenger car passes. This is the so-called masking effect: a quiet sound becomes completely inaudible if there is a strong sound source nearby. This effect, along with some others, is used in psychoacoustic models of modern codecs. The combination of conventional data compression methods and knowing what information is perceived by our brain and what is not, allows you to achieve a music compression ratio of 1:10 with an acceptable sound quality.
Below I have provided a brief overview of the most common and well-known music file compression formats that could be used to create a home music collection.
Wave file with ADPCM compression
The Microsoft ADPCM (Adaptive Differential Pulse Code Modulation) codec, once popular with hackers who didn’t want to waste time encoding MP3 music, is far from a quality standard. To reduce the file size, it was necessary to create wave files of eight or even four bits with a sample rate of 22 KHz, which gave a very weak result. And if an MP3 file with a fixed 128 Kb / s bit rate sounds more or less bearable (and ideal for some listeners), then a wave file of the same size compressed with the ADPCM codec sounds just awful.
ADPCM uses a very simple compression algorithm that provides high encoding speed on slower computers, but is completely inapplicable for storing music. The extremely low sound quality with an acceptable compression ratio led to the fact that at this time this codec is hardly ever used to compress music. The exception is computer games, whose creators often use ADPCM WAV files to store soundtracks.
MP3
MPEG (from the Motion Picture Expert Group) 1 Layer III (less often MPEG 2 Layer III), also known as incompetent people MPEG 3 (there is no such format) has for many years been the only association with the phrase “computer music” . Developed in the late 1980s, without requiring resources (playing MP3 files is possible even on computers with 486 processors), the format that allowed music to be compressed up to 10 times without catastrophic loss of quality quickly took root in computers. domestic. Although until recently most encoders were paid, it is now easy to find players and encoders distributed under the free software license. After a while, it became clear that “CD quality” at 128 Kb / s bit rate is impossible,
how equipping computers with more sophisticated sound cards and acoustic systems made it possible to identify the shortcomings of such encoding. Increasing the bitrate and improving the codecs became quite natural: VBR and Joint Stereo (combined stereo) technologies made it possible to significantly reduce file size while increasing quality. Modern encoders allow you to achieve sound quality, audibly indistinguishable from a CD at bit rates in the 192-256 Kb / s range, even on high-quality equipment. However, in some rare cases (in the presence of good hearing and equipment) even the 320 Kb / s bit rate is not enough.
