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A little of history


ADC/DAC

16 bits

44,1KHz it means CD quality

MIDI, synthesis FM and wave stage

Wave table for software

Polyphony (voices)

DSP

Channels, loudspeakers and the fever 3D

Sound specifications 3D

Digital Dolby or the movies at home

Autistic loudspeakers and company

Connecting our card with the exterior (and the other way round)

Formats or the fever of the MP3

References

Released page
4/27/2000


Author:
Miguel Tarazona "Skaug"
 

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MIDI, synthesis FM and wave stage

The digital sound has always had diverse formats (up to coming to mp3, the most fashionable at present). The sound in digital format has a problem, and it is his excessive space to store relatively little information. The calculations can be done easily: audio to 44,1KHz, with 16 bits and in stereo, gives us 172 Kb/segundo (10,3 MB per minute, an authentic atrocity).

This method of storing the digital audio "such a which" is the used one in the files.wav or in the CDs Audio. Nevertheless, it does not turn out to be useful for the professionals of the sector (especially for the composers); imagine the quantity of hard disk and, especially, memory that they are necessary to work to full yield with the digital audio. What is the possible solution? The format MIDI (Musical Instrument Data Interface)

Unlike the digital audio, the format MIDI is not the engraved sound, but principally the musical notes that compose it. Any file MIDI will occupy poquísimo space, because it is only necessary to store the notes that are sounding in every moment. The format MIDI was born to standardize the behavior of the different digital instruments, so that the same notes were sounding "equally" in the different instruments. Nowadays keyboards exist MIDI (the well-known synthesizers), pianos MIDI (like which I have at home), violins MIDI (Short Celts it has one, as well as The Corrs, which also use it), flutes MIDI, drummers MIDI, and even bagpipes MIDI (has anybody listened to any Hevia song?).

Well, in case of the computer, someone will have to be in charge of reproducing the compositions MIDI. And of course, the solution consists in making use of our sound card. As the format MIDI really any more you notice, we will have to obtain the sounds of some place, and two options exist.

The synthesis FM is the most economic. Until now, and long ago, it has been the most used solution. The synthesis FM is only a small processor that is in charge of imitating the sound by means of the employment of trigonometrical mathematical formulae (yes, I am not joking). And in certain way, it gives better results of the esperables.

For example: the sound of a classic stringed instrument is represented in the computer by means of a wave similar to the following one:

Graph representing the real sound of a stringed instrument

It is a question of a quite regular wave, which easily can be simulated by an equation.

Graph of the function bosom

All the equations are based on bosoms and cosines. For the one who does not know them, the equation of the bosom is that of the right, and that of the cosine is identical but displaced on the axis x pi/2 units.

If we construct from the previous equations a function (I have constructed one arbitrarily),

Trigonometrical mathematical function

we will obtain a wave species that in certain way looks alike to the one that we have digitized from a real instrument (more or less, too much... to the next one I will not struggle a little any more either)

Graph representing the previous function

Of course, the equations and functions that our sound card uses are much more complex and the much more similar waves, except in a case, in that of the percussion instruments, with much less stable waves, as it is appreciated in the following example:

Graph representing the sound of a percussion instrument

The solution that most of domestic cards ALREADY contribute (from the SoundBlaster AWE 32 and Gravis UltraSound), is the inclusion of the synthesis for wave Table (WaveTable). This is not any more that having the sounds of the engraved instruments (from real instruments) in a memory included in the proper card (ROM that normally it is possible to extend with RAM to add new and better sounds) or using the memory of the computer, in whose case will have to have connector PCI instead of ISA. With this we obtain a much major quality in the reproduction of songs MIDI.

At present only Crystal, SoundBlaster 16 and the compatible Yamaha OPL3 of 2000 ptas. (as well as some solutions integrated to basic badges and others of unknown manufacturer) they work without wave table. If you want to appreciate the sound difference, the following ones mp3 they show the difference of reproduction of a file MIDI between a sound card Crystal Sound System and for what a Yamaha XG would be necessary to expect of.

Certainly, if your audio software does not understand the files.mp3 (I have even although it understands them), recommend to you to unload the last version of the excellent program Winamp, which also supports many other types of file.

 

Wave table for software

Wave table synthesizer for Yamaha software

Is his card of synthesis FM? Not everything is lost, put that the second one mp3 also I recorded it with my Crystal, but using a virtual Yamaha synthesizer. This synthesizer works as a card would do it with wave table but using our processor to use the information (musical notes and effects to be applied).

You can unload it of www.yamaha-xg.com/english/xg/ and to prove his functioning in your own computer, to compare the quality of your sound card. Of course, we will be able to use our games with musician MIDI and will appreciate a notable increase of musical quality, straight proportional to the speed loss of the animations. It is necessary to bear in mind that these virtual synthesizers have the problem of consuming MANY CPU resources. Nevertheless we will be able to do an idea to ourselves if he is worth acquiring a sound card that incorporates wave table (although few ones will have the Yamaha quality in percussion instruments, they are really incredible).

 


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