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Hardware-software resources MP3

Evgenie Rudometov, Victor Rudometov.

Article is grounded on book substances "the PC Architecture, accessories, multimedia" —  SPb: Peter, 2000, 416 with.

In the course of evolution of resources of an information storage implementators permanently aspire to raise density of its allocation on carriers. During executable scientific and technical researches are perfected both carriers, and processing techniques, and algorithms of coding, writing and reading. Thus development of algorithms of information processing and is prompt vozrostajushchaja power of computing circuits often allow, not raising requirements to information capacity of carriers and changes of processing technique of writing to increase data recording/playback time. It is reached by usage of special algorithms of the compression (compression) realised by means of modern personal computers or arrangements on the basis of special processors concerning high efficiency. Such approach allows not only to use more effectively information capacity of existing carriers, but also gives the chance to realise essentially new writers, processings, storages and information playback. Often such arrangements give to the user the new functionality unavailable earlier. It concerns both video, and audio.

In the course of perfection of algorithms of compression the effective method of a compression of the sound information MPEG, actually become to one of widespread standards has been developed. It quite often name as MPEG 1 Layer 3, MPEG 3, MP3. Last is most often used name.

The algorithms taken as a principle of standard MP3, consider psychophysiological features of human hearing. The given algorithms allow to reduce essentially the size of a usual sound wav-file, discarding insignificant units of a track. It is necessary to consider, that given preobrazovante it is carried out with loss of a part of the sound information. However the appropriate choice of parametres of coding possible to minimise these losses and to reach a comprehensible degree of quality. The optimal set of parametres allows to save completely practically, as a rule, initial quality of sounding at essential saving of an information field of the carrier. The used algorithms of compression realising standard MP3 are effective enough and perfect. Even at considerable compression, for example, in 10 times losses as pieces of music often are not felt, especially, if they do not differ a wide dynamic range. All it promoted wide implantation and popularisation of the given standard. The encoded files owing to reduction of their size are easier for storing, duplicating or handling, for example, using communication facilities. Standard MP3 became a popular transmission medium of the sound information in an Internet network. Besides, began popular to create collections of files mp3 and to write them on become by already traditional CD-ROMs, CD-R, CD-RW. Thus on one CD-ROM of standard size the information of the several usual, not compressed, musical disks, for example, the information 10 CDs can go in. All depends on a degree of a compression, features of the sound information and demanded quality of playback after dekompressii. The transformed files have more often mp3 extension.

Usually writing and playback of the compressed sound information is carried out by means of the special programs which are carrying out on the computer a compression and dekompressiju of files. However the portable arrangements are already released, capable to play back and even to write files under standard MP3.

File creation mp3 from musical CD shares on two stages: reading c CD and writing of a demanded composition in a usual wav-file on the computer and the subsequent coding of this file for the purpose of creation of a file of the compressed information with mp3 extension.

Conversion to format MP3 is carried out according to the special algorithms of compression realising the requirements of the standard. Coding is characterised by a compression degree — an aspect ratio. The value of the given coefficient is directly linked to the demanded quality of the sound information received in the course of the subsequent decoding. The the file is more compressed, the it is more than loss in the initial information and more low quality of the decoded signal.

Quality of playback of a file mp3 is characterised by sampling rate, for example, 44,1 kgts, digit capacity, for example, 16 bits, quantity of channels — a mono/stereo. And very important parametre is the value of a stream of the information (bit rate), received in the course of a compression. At coding performance in which result conversion of a wav-file to a file mp3 is carried out, all four parametres are selected.

For excellence reaching CD parametres — 44,1 kgts, 16 bits, a stereo use   . At a compression it is possible to select the different value of a stream, for example: 64, 98, 128, 192, 256 Кбит/c etc . The more the stream value, the above will be quality of playback of the sound information, but more low the value of an aspect ratio (compression) and, accordingly, is more volume the resultant file mp3 will turn out.

By the way, it is necessary to mark, what even at low values of a stream the high level of a dynamic range limited only to features of an initial signal is provided very much. And at information copying this level is completely saved. It it is impossible to tell concerning operations with the traditional cassette tape recorder which magnetic tapes even very much excellence, even at usage shumopodavitelja are characterised rather by high level of noise and accordingly limit a dynamic range. Especially it concerns the subsequent copying when levels of noise and deformations fast increase for each subsequent copy. Excellence and identity of copies also are the major characteristics which distinguish the digital methods taken as a principle MP3 and CD, from analogue ways of the previous generation of arrangements of conversion of the information.

Usually the stream suffices for coding of speech by means of algorithms MP3 64 Kbit/with. The choice of such stream practically does not affect quality, but allows to compress effectively the sound information, saving a carrier information field.

For music coding the stream 128 uses Kbit/with, that corresponds approximately to an aspect ratio 11. Expert estimations confirm, that the stream in 128 Кбит/c provides rather the excellence close to CD, especially on level of noise. First of all it concerns type music pop, rock, etc . Such music is characterised, as a rule, by rather low dynamic range and rather narrow frequency spectrum. The specified stream became the actual standard for coding of such type of the sound information. Nevertheless, despite all advantages of coding with a stream 128 Kbit/with, many experts all the same consider, that really excellence, really, not conceding CD, streams, since 256 value provide only Kbit/with. By the way, the stream 256 Kbit/with corresponds to an aspect ratio approximately 5. For the purpose of excellence reaching cases of usage of a stream 256 Kbit/with, especially in case of coding of classical music are frequent .

Recommended parametres of coding


Stream, Kbit/with

Input signal, Hz

Sampling rate, kgts


32 (16)


16 (8)

Radio FM




The tape recorder












Studio recording




Estimating quality of a track on CD, the subjected compression on MP3, it is necessary to consider, that, unfortunately, there are also deceit cases, some kind of swindle in sphere of coding of the sound information. For example, for engaging of buyers on a disk with classical music in a format mp3 often write, that the irresistible quality of sounding provided with coding with a stream, corresponding to 256 value Kbit/with, and actually only 128 is guaranteed  Kbit/with, that, certainly, is inadmissible.

Working with files mp3, not without fail to be oriented only to special CDs with already encoded information with streams 128 Kbit/with or 256 Kbit/with. Such CDs are released in a considerable quantity by numerous corporations of a sound recording. At independent creation of files mp3 as sources of the sound information of excellence traditional audio of CD can be used. As a rule, modern CD-ROM drives have special function of reading of audiodata from musical compact discs — Reading Raw Audio Stream — RA (Raw Audio). The users having such drive, can take advantage of special programs which provide conversion of the specified audiotrack to a wav-file. These are the so-called programs-grabbery which considerable quantity can be found in the Internet. For an example such programs, as AudioGrabber, CD2WAV, CDCOPY, CDDA, CDGRAB and others can be.

Program AudioGrabber except wav-file creation, allows, to adjust level of writing and to encode a wav-file in a file mp3. It is necessary to mark, that early versions of this program worked only with the arrangements supporting RA. However in the last versions of the program the intrinsic function of analogue copying of the information from musical CD through a sound map. It allows to use drives without support RA. The example of operation of program AudioGrabber is resulted on fig. 1.

Fig. 1. Program AudioGrabber

Unfortunately, the programs providing conversion of an audio-track in a wav-file, as a rule, do not work with the CD-ROM drives which are not supporting RA. Such drives, as a rule, concern already become outdated, but rather often used nizkoskorostnye arrangements. It, for example, drives 2х, 4х, 6х. For similar drives it is possible to take advantage of the alternative resources providing performance of the given task. For example, one of ways is simultaneously to lose a musical disk and to write the sound information through a sound map to a hard disk by means of, for example, PLAYFILE or any other suitable program of creation of a wav-file.

Further as the tool for conversion of a wav-file to a file mp3 it is possible to use the popular and repeatedly checked up program L3ENC using algorithm Fraunhofer-IIS.

It is necessary to mark, that coding time is great enough. For computers of a class 486 conversion of a 5-minute tune by means of program L3ENC with a set value of a stream 128 Kbit/with demands approximately 2-3 hours. On the computer with the processor of Pentium-166 MMX the same operation is fulfilled for 20–30 minutes. However the computer with the processor of Pentium II-266 copes with such task for 5-10 minutes. In case of usage of the computer with the processor of Pentium III operation can be fulfilled already in real time.

Certainly, except the specified program, there are also many other things programs for creation of files mp3. Many of them encode fast and qualitatively. Some of these programs use more perfect algorithms, than for resulted L3ENC. Thus a part of programs it is oriented to low values of streams — 128 Kbit/with and less, and another — on high — 256 Kbit/with and more. But irrespective of used algorithms for listening of the encoded files the same programs can be used, as a rule.

For playing of already ready files mp3 in the market of software products it is possible to select two the most popular is WinAmp and WinPlay. WinPlay is the simple enough program, allowing to lose mp3-files with high quality even on computers of a class 486. Program operation is presented on fig. 2.

Fig. 2. Program WinPlay.

Program WinAmp is the most popular player. It has some additional possibilities in comparison with others, for example, a graphics equalizer, analyzers of a signal and many other things. Program operation is presented on fig. 3.

Fig. 3. Program WinAmp.

File playing mp3требует from the computer is enough high efficiency. Often happens so, that the computer does not cope with fast decoding: in the course of playback the effect of intermittence of sounding is observed. Especially it concerns computers of a class 486. However and in this case there is a possibility of playing of a tune, the truth, with the worst quality. For example, in program-player customisations it is possible to lower frequency twice, to disable a stereo etc . It is necessary to mark, that in most cases on the basis of Pentium processor (and the more so Pentium II) is enough computer power for support of necessary speed dekompressii, and also implementations of possibilities of the numerous special effects given by programs.

Considering and parsing possibilities of modern computers, it is necessary to mark, that for playback of files mp3 it is possible to use not only computers, but also specialised arrangements.

Player Diamond Rio PMP300 of Diamond corporation became one of the first portable players intended for playing of files mp3. This arrangement is characterised by the wide frequency range making 20 Hz-20 kgts at a relation a signal/noise more 90 db, low harmonious deformations — 0,01–0,1 %, a power output more than 50 mvt. The arrangement sizes — 89x64x16 mm, weight — 70 Power supply is carried out from one unit of type AA 1,5 V.Fajly mp3 are prepared by means of the specialised software on the computer, arrangement hooking up to which is carried out through port LPT. Ready files can be received and through an Internet network. The given player allows to store approximately 30 minutes of a qualitative sound at a stream of 128 Kb\ss.

One more arrangement is MPIO Daewoo corporations. This portable instrument provides not only playback of files mp3, but also writing of the sound information. As well as the previous arrangement, MPIO is characterised by a wide frequency range, a low level of noise and deformations. Hooking up to the computer is carried out through port LPT. In structure MPIO graphics display LCD and the built in microphone use. Variants with a FM-tuner and-or the video unit for usage of the given arrangement as the digital camera are provided.

Alternatively specified arrangements can result a player raveMP Sensory Science corporations. The built in memory is increased to 64 Mb. The arrangement allows not only to play back, but also to carry out writing till 4 o'clock a sound through the built in microphone.

As information storage resources in portable players of files mp3 CD-ROMs, or even hard disks can appear, for example. As an example it is possible to result MP3 Shuttle and MP3 Shuttle II Xeenon corporations which use for storage of files mp3 according to CD-ROM and a hard disk. The player of MP3-ROM of MacPower corporation allows to use practically all modern media as CD-ROM, DVD, etc. Thomson Multimedia — the player of mp3-files of Lyra corporation, as the medium will use a miniature hard disk in size of 340 Mb, recently developed by IBM.

As to perspectives it is necessary to mark, that CompactFlash Association is gathered to build in structure of the flesh-memory maps used in players, USB controllers which will allow in a local mode with ease to read out from a map and to write on a map the necessary information.

All aforesaid illustrates that fact, that, despite a resistance of some corporations of the sound recording initiating development of alternative standards of a sound recording, interfering unauthorized copying of the audioinformation, algorithms MP3 continue to develop, winning new supporters. Professional implementators and enthusiasts MP3 offer the improved algorithms, programmers create new programs, and the electronic industry releases all new and new arrangements.


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