Friday, November 22, 2013

Binary Code

Computers use binary code to store or transmit data. It is a very simple language. Binary code is very absolute, there is no in-between.

  • yes or no
  • on or off
  • light or no light
  • reflection or no reflection
  • magnetic flux or no magnetic flux
  • voltage or no voltage
  • one or zero

Each piece of the binary code is a bit (a contraction of the phrase, “binary digit”). The bits are usually grouped in eights for organizational purposes, also called bytes (a contraction of the phrase, “by eight”). On a side note, a group of four bits is called a nibble, which is a small byte (ha! Get it?!)

Bits (abbreviated with a lowercase b) are usually used when referring to transmission speeds or compression rates.

  • 128kb/s mp3 file
  • 9.8Mb/s video stream

Bytes (abbreviated with an uppercase B) are usually used when referring to file size or drive space.

  • 8 GB RAM
  • 1 TB HDD


Bit b 1 bit
Kilobit kb 1024 bits
Megabit mb 10242 bits 1024 kilobits
Gigabit Gb 10243 bits 1024 megabits
Terabit Tb 10244 bits 1024 gigabits

Bits typically use the binary prefix (210 = 1024) for kilo-, mega-, etc.

Byte B 1 byte
Kilobyte kB 1 thousand bytes
Megabyte MB 1 million bytes 1 thousand kilobytes
Gigabyte GB 1 billion bytes 1 thousand megabytes
Terabyte TB 1 trillion bytes 1 thousand gigabytes

Bytes typically use the Internation System of Units (SI) prefix for kilo-, mega-, etc.

Monday, March 25, 2013

Common Sampling Rates

  • 44.1 kHz - Used for audio CDs and audio content on DVDs. Generally considered as the standard sample rate for music.
  • 48 kHz - Originally used on digital audio tapes (DAT) (an early consumer digital recording format) as a way to prevent copying the audio from a CD. Currently used on DVDs and digital video recording formats. Generally considered as the standard sample rate for audio-for-video.
  • 88.2 kHz - Double the sample rate of a CD. Used during production of music when the final consumer format will be CD (the conversion from 88.2 kHz to 44.1 kHz is easy for a computer to do).
  • 96 kHz - Double the sample rate of audio-for-video. Used during production when the final consumer format will be audio-for-video (the conversion from 96 kHz to 48 kHz is easy for a computer to do). Also converts to 32 kHz easily.
  • 176.4 kHz & 192 kHz - Quadruple the consumer formats. Used for the highest possible quality recordings such as archival recordings or when the recording will potentially need intense processing, e.g. pitch shifting.
  • 32 kHz - Audio sample rate of broadcast video (over-the-air, cable, or satellite television). Also used in streaming audio applications such as HD or satellite radio
  • 8 kHz - Used in telephone quality audio as well as podcasting.

Tuesday, February 19, 2013

Data Compression

Data compression is a method of reducing the file size for conserving drive space or easier transfer. Data compression comes in three forms:

  • Archival
    • A lossless method of packing a file into a smaller space.
    • The file will need to be unpacked before using.
    • Also useful for collecting multiple files into one package for transfer.
    • Examples include zip, rar, tar, gz.
  • Lossless
    • A method of reducing the size of a file by removing statistical redundancies.
    • When the file is decompressed, the result should be identical to the original.
    • The file is decompressed by the decoder in real-time for consumption.
    • Examples include flac, alac.
  • Lossy
    • A method of reducing the size of a file by removing irrelevant information.
      • The information is gone forever.
    • Irrelevancy of information is determined by the codec used.
      • The codec determines irrelevant information based on psychovisual or psychoacoustic models.
    • Benefits include reduced disk space and bandwidth use.
    • Examples include jpeg, mp3.

Sunday, February 17, 2013

Compression Artifacts

Compression reduces the data needed to represent the image, audio, or video. During lossy compression, artifacts (errors) are created as a side effect. These artifacts may or may not have an impact on the quality of the resultant file. Whether or not this occurs is based on the complexity of the algorithm used during compression.

Processing power and compression algorithms are interrelated. A more powerful processor can execute a more complex algorithm more efficiently (i.e.: in less time). A newer, more complex compression algorithm can be introduced because newer, more powerful processors can handle it.

Thursday, February 14, 2013

Free Images Online

Color Spaces

  • RGB is used for illuminating color
    • Red, Green, and Blue light are added together
  • YUV is used for transmitting color
    • YCbCr is the digital version
    • Y is the luminance
    • U is the blue-difference
    • V is the red-difference
  • CMYK is used for printing color
  • HSV is used in digital image editing
    • Hue, Saturation, Value

Color Spaces on Wikipedia.