3.5.6.7 Data compression, 3.5.6.6 Musical Intstrument Digital Interface (MIDI) Flashcards
What is lossy compression? What is the product of lossy comprsssion on the original file?
A type of compression in which data is permanently discarded.
This results in the decompressed file being an approximation of the original
Give 4 examples of lossy compression formats
MP3 (Motion Pictures Expert Group Audio Layer 3)- Audio file
JPEG (Joint Photographic Experts Group)- Image files
MPEG-1 (Motion Pictures Expert Group) - Video files; suitable for small screen, low resolution video
MPEG-2 (Motion Pictures Expert Group) - Video files: suitable for full screen , high resolution video
Why is lossy compression viable if it causes permanent data loss?
Data in sound and image files can be lost without a noticeable effect on quality, because the human eye and ear cannot detect or distinguish between small changes
When is lossy compression NOT viable?
For important text files that contain letters and numbers where no data can be lost.
(Imagine trying to recreate a word where you have a few missing letters here and there, this would no longer be an approximation as the original file is unrecognisable)
What is the risk of lossy compression?
It is a destructive process, which means original data is lost . This means if lossy compression is repeatedly done on one file, it will eventually become unrecognisable.
What is lossless compression?
Compression techniques in which no data is lost.
The original file is identical to the decompressed file.
Give 3 lossless compression formats
PNG (Portable Network Graphic) - Images that must retain highest level of quality
GIF (Graphics Interchange Format) - Images and short animations
ZIP (N/A;Not an acronym) - Used to compress one or more files together
What is dictionary-based compression? What is the drawback?
A lossless method of compression in which each repeated pattern is given a smaller code than it’s binary representation, reducing the amount of bits needed to store the data.
However, a dictionary file explaining what each code means has to be appended , which increases size.
What is RLE?
Run Length Encoding is a method of lossless compression where repeated runs of binary patterns and replacing them with a single instance of the number and how another digit for how often it occurs.
What is the Nyquist theorem?
It states that the sampling rate must be atleast twice the maximum frequency at any point of the sound wave, so that the sound maybe accurately represented.
How does midi work? how do they differ from sound files?
It uses a series of instructions called “event messages” to explain what notes should be played, how they should be played, and when they should be played.
MIDI files hold signals rather than digital representations of analogue sound, such as:
Digital signals that specify notation, pitch, and intensity
Control signal for parameters like volume and vibrato
clock signals to set the tempo
What is MIDI?
MIDI is a technical standard that includes protocols and hardware specifications for the communication of electronic musical instruments and computers to produce and manipulate music
What is the advantage and disadvantage of MIDI?
It uses less storage space that sampled recording
it can be easily manipulated to get the desired sound
it may not often sound realistic and sound computerised/electronic
