Page 229 - DCAP303_MULTIMEDIA_SYSTEMS

Unit 13: Multimedia Tools for WWW

represented as a computer command. When the MIDI device processes this command, the result notes
will be the sound from the guitar. The protocol provides an effective means of conveying musical
information as electronic data. Since MIDI files are small in size, these can be embedded while
loading of Web pages and promptly played. Length of the MIDI files can be changed without
degrading the quality of the signal. As the signals are stored as the notes played on the musical
instrument, working on the MIDI files require knowledge of the music theory. The MIDI data
stream is a unidirectional asynchronous bit stream at 31.25 Kbits/sec with 10 bits transmitted per
byte (a start bit, 8 data bits, and one stop bit). The MIDI interface includes three different MIDI
connectors, labeled as IN, OUT, and THRU. The MIDI data stream is usually originated by a MIDI
controller, such as a musical instrument keyboard, or by a MIDI sequencer. A MIDI controller is
a device which is played as an instrument, and it translates that into a MIDI data stream in real
time. A MIDI sequencer is a device which allows MIDI data sequences to be captured, stored,
edited, combined, and replayed. The MIDI data output from a MIDI controller or sequencer
is transmitted via the devices’ MIDI OUT connector. The recipient of this MIDI data stream is
commonly a MIDI sound generator or sound module, which will receive MIDI messages at its
MIDI IN connector, and respond to these messages by playing sounds. Figure 13.2 shows a simple
MIDI system, consisting of a MIDI keyboard controller and a MIDI sound module.
figure 13.2: MiDi interface

MIDI OUT

MIDI IN
Keyboard
SOUND
MIDI IN MIDI
MIDI OUT
MIDI IN
MIDI
DRUM
MACHINE

13.6.3 Comparison between MiDi and Digitized audio
Comparison MiDi Digitized audio
Representation Shorthand representation of Sampling is done to convert the data
music stored in numeric form into digital form
Device Independence Device dependent Device Independent
File Size 200 to 1000 times smaller than Larger File Size
Digitized Audio
Memory Requirement Less storage space Large Storage space
Edit Options Easily editable and all the Difficult to edit.
information retainable
Quality Better when played on high Not so better
quality MIDI device
Playback Does not have consistent Consistent playback quality
playback quality

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