Tag: what is digital audio output

Hardware for processing digital audio – Part 4

Hardware for processing digital audio – Part 4

digital audio processing

As a practical example of a MIDI device, consider a conventional MIDI keyboard.

DIGITAL AUDIO PROCESSING MAC

Simplified, a MIDI keyboard is a shortened grand piano keyboard in a housing that contains a MIDI interface that allows you to connect it to other MIDI devices, such as a MIDI synthesizer, that is installed on your computer’s sound card. With special software (for example, a MIDI sequencer), you can turn a MIDI synthesizer into play mode, for example, on a grand piano, and by pressing the keys on a MIDI keyboard, you can hear the sounds of a piano from line. Naturally, the matter is not limited to the grand piano: in the GM standard there are 128 melodic instruments and 46 percussion instruments. Additionally, using a MIDI sequencer, you can record notes played on a MIDI keyboard on a computer for further editing and arrangement, or simply to print notes.

It should be noted that since MIDI data is a set of commands, music written using MIDI is also recorded using synthesizer commands. In other words, a MIDI score is a sequence of commands: what note to play, what instrument to use, how much and how much it will sound, etc. Familiar MIDI files (.MID) are more than just a collection of such commands. Naturally, since there are a large number of MIDI synthesizer manufacturers, the same file can sound differently on different synthesizers (because the instruments themselves are not stored in the file, there are only instructions to the synthesizer on which instruments to play. while the differences synths may sound different).

Let’s go back to the consideration of sound cards. As we have already clarified what MIDI is, we cannot ignore the characteristics of the hardware synthesizer built into the sound card. A modern synthesizer, most often, is based on the so-called “wave table” – WaveTable (in short, the principle of operation of such a synthesizer is that the sound in it is synthesized from a set of recorded sounds dynamically superimposing them and change of sound parameters), before the main synthesis type was FM (Frequency modulation: sound synthesis generating simple sinusoidal oscillations and mixing them). The main characteristics of a WT synthesizer are: the number of instruments in the ROM and their volume, the presence of RAM and its maximum volume, the number of possible signal processing effects, as well as the possibility of channel-by-channel effect processing. . (of course, in the case of an effects processor), the number of oscillators that determines the maximum number of voices in polyphonic mode (polyphonic) and, perhaps most importantly, the standard by which the synthesizer is manufactured (GM , GS or XG). By the way, the amount of memory of the synthesizer is not always a fixed value. The thing is that recently synthesizers have stopped having their own ROM, but use the main RAM of the computer: in this case, all the sounds used by the synthesizer are stored in a file on disk and, if necessary, are they read into RAM.

Hardware for processing digital audio – Part 3

Hardware for processing digital audio – Part 3

digital audio processing

A MIDI synthesizer is a synthesizer that meets the requirements of the standard that we will now talk about. MIDI is a generally accepted specification related to the organization of a digital interface for musical devices, which includes a standard for hardware and software.

Digital Audio Processing

This specification is intended to organize a local area network of electronic instruments (Fig. 7). MIDI devices include a variety of musical instruments and hardware that meet MIDI requirements. Therefore, a MIDI synthesizer is a musical instrument, generally intended to synthesize sound and music, and also conforming to the MIDI specification. Let’s briefly see why there is a separate class of devices called MIDI.

The fact is that the implementation of sound processing software is often associated with drawbacks due to various technical characteristics of this process. Even leaving sound processing operations on a sound card or any other equipment, many different problems remain. First, it is often desirable to use hardware synthesis of musical instrument sounds (at least because a computer is too general an instrument, often only a hardware sound and music synthesizer is needed, nothing more). Second, software sound processing is often accompanied by time delays, while concerted work requires instantaneous reception of the processed signal. For these and other reasons, they resort to the use of special equipment for processing, and not computers with special programs. However, when using equipment, there is a need for a single standard that allows devices to connect to each other and combine. It was these prerequisites that led several leading companies in the musical equipment field to approve the first MIDI standard in 1982, which was subsequently continued and continues to this day. What, ultimately, is a MIDI interface and the devices included in it from a personal computer’s point of view?

Hardware: These are installed on the sound card: a synthesizer of various sounds and musical instruments, a microprocessor that controls and controls the operation of MIDI devices, as well as several standardized connectors and cables for connecting additional devices.
Programmatics is a MIDI protocol, which is a set of messages (commands) that describe various functions of the MIDI system and with which communication (information exchange) between MIDI devices takes place. The messages can be considered as a means of remote control.
The scope of this article does not allow us to delve into the description of MIDI in particular, it should be noted, however, that with respect to sound synthesizers, MIDI sets strict requirements for their capabilities, the sound synthesis methods used in them. , as well as for the synthesis control parameters. Furthermore, in order for music created on one synthesizer to be easily transferred and played successfully on another, several standards have been established for the matching of instruments (voices) and their parameters on various synthesizers: the General MIDI (GM) standard, General Synth (GS) and eXtended General (XG). The basic standard is GM, the other two are its logical extensions and extensions.