T2 - Sound + Compression Flashcards
Analogue sound signals are which type of data
continuous.
Digital signals are which type of data
discrete.
How Sound is digitized:
by repeatedly measuring + recording the sound wave
A to D converters:
Sounds is converted to a digital form
= stored + processed by a computer
An Analogue to Digital Convertor (ADC) is used for
to convert inputs to digital signals.
A Digital to Audio Convertor (DAC) is used for
to convert digital signals to outputs.
Sound sampling -
measurement of amplitude of a
sound wave at a given time
How is sound sampled:
- Sound is sampled using a bit depth and sample rate
what does bit depth determine in sound sampling
determines how closely the wave is sampled on the y-axis
Sampling rate -
number of samples taken per second
(Hz)
Sample resolution:
The number of bits used to record
each measurement
More bits used per sample =
- the height of the wave to be more accurately measured
- increases file size
Hertz
- 1Hz = 1 sample per second
sample resolution aka
audio bit depth
Sampling rate frequency:
The greater the frequency, the greater the accuracy, and file size
Calculating sound file sizes:
sample rate * bit depth * duration
Recording quality improves: as a result of
the more frequent
the more accurately recorded the wave height
Increasing the sampling rate (frequency) =
means recording more data points
Increasing the bit-rate =
improves the accuracy of each data point
Lossy compression:
removes sounds that
we can’t easily hear or that is unnecessary
Lossy compression cons:
-leaves out some data
=affects quality
Lossy compression pros:
useful for storing,
downloading or streaming
-as it is smaller
Lossless compression:
-reduce the file size
when compressed but do not
lose any information
-can be decompressed
Eg of lossless:
FLAC (Free Lossless Audio Codec)
ALAC (Apple Lossless Audio Codec)
WMA Lossless (Windows Media Audio)
Uses of compression:
often used for files and data that are sent via the internet
Download times are reduced
Data allowances go further
No lagging
Benefits of compression: (6)
- Smaller files = fewer packets = faster transmission time
- Quicker to complete transmission
- Reduces traffic over the Internet
- Reduces download times
- Images inside web pages appear faster
- Reduces space on disk / servers
no lagging means
= transmission of
video + music data streams as fast as they are playing
