File format name
|
What type of information or data is it?
|
Compression?
uncompressed, lossy, lossless |
How does it work?
(just a few brief words about the theory behind the encoding or compression) |
BMP
(bitmap)
|
Raster image file
|
uncompressed(lossless)
|
Indexed images can be compressed with a 4 or 8 bit Huffman algorithm. All images can be stored uncompressed. 16 and 32 bpp images are usually stored uncompressed.
|
JPEG
(or JPG) |
Pictures
|
lossy
|
Has an optional lossless format. Standard image format. Most images on the internet are jpegs. Typically uses 10:1 compression ratio.
|
WAV
|
Audio file
|
uncompressed
|
This uses the Linear Pulse Code Modulation Format which retains all samples of audio. It stores two channel audio sampled 44,100 times per second with 16 bits per sample
|
PNG
|
Replacements for GIF
|
lossless
|
Improved replacement for GIF format. It uses precompression filtering where it predicts the value of a byte and it encodes the difference between the predicted value and the actual value. Next, it uses the lossless DEFLATE compression algorithm.
|
MP3
|
Audio
|
lossy
|
Common encoding rate: 128 kilobits per second. A compressed mp3 file typically achieves a 75%-95% compression rate so the size of the compressed file is ¼ or 1/20 of the original file.
|
GIF
|
Image File
|
lossy
|
This is type of bitmap image format. It supports 8 bits per pixlel for each image. It also supports animation with up to 256 colors per frame. The compression technique used is LZW compression which is lossless and uses a dictionary to index deleted information.
|
ZIP
|
File storage
|
lossless
|
Most commonly uses the DEFLATE algorithm which is similar to the Huffman encoding algorithm. It reduces replaces commonly used symbols with shorter representations and less commonly used symbols with longer representation.
|
Question: What other file type(s) have you heard of? Which one would you like to know the most about?
MP4, .mov, .ppt, .docxIt is important to know the different file sizes and how they use compression to manage file size. There are two types of compression: lossy and lossless. Lossy compression throws out redundant data from the file which means that files that use lossy compression are often lower quality than uncompressed or lossless files. Lossless files are higher quality but the main disadvantage is that they are often giant files that are hard to store. Most files that use lossless compression store data in a dictionary where they can retrieve it when the file is used. People can analyze the quality to size ratio and determine which file best suites their needs.
Further Resources:
https://www.youtube.com/watch?v=guo8if4Yxhw
https://www.youtube.com/watch?v=By30SCp-Tsw
https://www.youtube.com/watch?v=Lto-ajuqW3w
https://www.youtube.com/watch?v=Lto-ajuqW3w
