User talk:Ksaareme
From ICO wiki
Truth Tables
Logical Conjunction(AND) p q p ∧ q T T T T F F F T F F F F
Logical Disjunction(OR) p q p ∨ q T T T T F T F T T F F F
Logical NAND p q p ↑ q T T F T F T F T T F F T
Logical NOR p q p ↓ q T T F T F F F T F F F T
Compression
Data compression ratio is defined as the ratio between the uncompressed size and compressed size:
Compression Ratio = Uncompressed Size / Compressed Size
Thus a representation that compresses a 10MB file to 2MB has a compression ratio of 10/2 = 5, often notated as an explicit ratio, 5:1 (read "five" to "one"), or as an implicit ratio, 5/1. Note that this formulation applies equally for compression, where the uncompressed size is that of the original; and for decompression, where the uncompressed size is that of the reproduction.
Sometimes the space savings is given instead, which is defined as the reduction in size relative to the uncompressed size:
Space Savings = 1 - Compressed Size / Uncompressed Size
Thus a representation that compresses a 10MB file to 2MB would yield a space savings of 1 - 2/10 = 0.8, often notated as a percentage, 80%.
For signals of indefinite size, such as streaming audio and video, the compression ratio is defined in terms of uncompressed and compressed data rates instead of data sizes:
Compression Ratio = Uncompressed Data Rate/ Compressed Data Rate
and instead of space savings, one speaks of data-rate savings, which is defined as the data-rate reduction relative to the uncompressed data rate:
Data Rate Savings = 1 - Compressed Data Rate / Uncompressed Data Rate
For example, uncompressed songs in CD format have a data rate of 16 bits/channel x 2 channels x 44.1 kHz ≅ 1.4 Mbit/s, whereas AAC files on an iPod are typically compressed to 128 kbit/s, yielding a compression ratio of 10.9, for a data-rate savings of 0.91, or 91%.
When the uncompressed data rate is known, the compression ratio can be inferred from the compressed data rate.
Bits and Bytes
bit byte bit 1 0.125 byte 8 1
Notes:The value of K (Kilo) during calculations can take two values 1024 or 1000, depends on which type of calculation you want to perform. Consider using K = 1024 when you are considering storage capacity whether in hard disk, DVDs, flash drives or other devices and storage media. K = 1000 should be used when you are thinking of throughput, ie the speed at which information is transferred.
Example: If your computer has 1 KB of disk space is says that he has 1024 B of space, now the throughput of your network card is 1 KB/s then it is said that it transmits data to 1000 B/s.
Bit (b) Byte (B) Kilobit (Kb) Kilobyte (KB) Megabit (Mb) Megabyte (MB) Gigabit (Gb) Gigabyte (GB)
Binary Equivalents 1 Nybble (or nibble) = 4 bits 1 Byte = 2 nybbles = 8 bits 1 Kilobyte (KB) = 1024 bytes 1 Megabyte (MB) = 1024 kilobytes = 1,048,576 bytes 1 Gigabyte (GB) = 1024 megabytes = 1,073,741,824 bytes
Show addition of X and Y in binary 0 + 0 = 0 0 + 1 = 1 1 + 0 = 1 1 + 1 = 0, and carry 1 to the next more significant bit
Show subtraction of X and Y in binary 0 - 0 = 0 0 - 1 = 1, and borrow 1 from the next more significant bit 1 - 0 = 1 1 - 1 = 0
Show multiplication of X and Y in binary 0 x 0 = 0 0 x 1 = 0 1 x 0 = 0 1 x 1 = 1, and no carry or borrow bits
Git
The object database contains four types of objects:
A blob (binary large object) is the content of a file. Blobs have no file name, time stamps, or other metadata. A tree object is the equivalent of a directory. It contains a list of file names, each with some type bits and the name of a blob or tree object that is that file, symbolic link, or directory's contents. This object describes a snapshot of the source tree. A commit object links tree objects together into a history. It contains the name of a tree object (of the top-level source directory), a time stamp, a log message, and the names of zero or more parent commit objects. A tag object is a container that contains reference to another object and can hold additional meta-data related to another object. Most commonly, it is used to store a digital signature of a commit object corresponding to a particular release of the data being tracked by Git.
heads refers to an object locally. remotes refers to an object which exists in a remote repository. stash refers to an object not yet committed. meta e.g. a configuration in a bare repository, user rights. The refs/meta/config namespace was introduced resp gets used by Gerrit (software)[clarification needed][45] tags see above.
Common Usage
create a new repository create a new directory, open it and perform a git init to create a new git repository.
checkout a repository create a working copy of a local repository by running the command git clone /path/to/repository when using a remote server, your command will be git clone username@host:/path/to/repository
workflow your local repository consists of three "trees" maintained by git. the first one is your Working Directory which holds the actual files. the second one is the Index which acts as a staging area and finally the HEAD which points to the last commit you've made.
add & commit You can propose changes (add it to the Index) using git add <filename> git add * This is the first step in the basic git workflow. To actually commit these changes use git commit -m "Commit message" Now the file is committed to the HEAD, but not in your remote repository yet.
pushing changes Your changes are now in the HEAD of your local working copy. To send those changes to your remote repository, execute git push origin master Change master to whatever branch you want to push your changes to. If you have not cloned an existing repository and want to connect your repository to a remote server, you need to add it with git remote add origin <server> Now you are able to push your changes to the selected remote server
update & merge to update your local repository to the newest commit, execute git pull in your working directory to fetch and merge remote changes. to merge another branch into your active branch (e.g. master), use git merge <branch> in both cases git tries to auto-merge changes. Unfortunately, this is not always possible and results in conflicts. You are responsible to merge those conflicts manually by editing the files shown by git. After changing, you need to mark them as merged with git add <filename> before merging changes, you can also preview them by using git diff <source_branch> <target_branch>
replace local changes In case you did something wrong, which for sure never happens ;), you can replace local changes using the command git checkout -- <filename> this replaces the changes in your working tree with the last content in HEAD. Changes already added to the index, as well as new files, will be kept. If you instead want to drop all your local changes and commits, fetch the latest history from the server and point your local master branch at it like this git fetch origin git reset --hard origin/master
log in its simplest form, you can study repository history using.. git log You can add a lot of parameters to make the log look like what you want. To see only the commits of a certain author: git log --author=bob To see a very compressed log where each commit is one line: git log --pretty=oneline Or maybe you want to see an ASCII art tree of all the branches, decorated with the names of tags and branches: git log --graph --oneline --decorate --all See only which files have changed: git log --name-status These are just a few of the possible parameters you can use. For more, see git log --help
tagging it's recommended to create tags for software releases. this is a known concept, which also exists in SVN. You can create a new tag named 1.0.0 by executing git tag 1.0.0 1b2e1d63ff the 1b2e1d63ff stands for the first 10 characters of the commit id you want to reference with your tag. You can get the commit id by looking at the...
Decimal <--> Hexadecimal
Hexadecimal Decimal
0 0
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
A 10
B 11
C 12
D 13
E 14
F 15
Radio station is streaming MP3 audio at 192kbps. How many 500GB harddisks are required in order to archive 8 years of shows?
192 kbps = 192 000 bps
1 536 000 Bps
1500 Kb/s 1.46484375 MB/s
8 years = 2920 days = 70080 hours = 4204800 minutes = 252288000 seconds
172 228608 MB
16 8192 GB
336.384 500GB harddrives
Audio and Images
Audio In digital audio, 44,100 Hz (alternately represented as 44.1 kHz) is a common sampling frequency. Analog audio is recorded by sampling it 44,100 times per second, and then these samples are used to reconstruct the audio signal when playing it back.
Images PNG supports palette-based images (with palettes of 24-bit RGB or 32-bit RGBA colors), grayscale images (with or without alpha channel), and full-color non-palette-based RGB[A] images (with or without alpha channel). PNG was designed for transferring images on the Internet, not for professional-quality print graphics, and therefore does not support non-RGB color spaces such as CMYK.
JPEG/JFIF supports a maximum image size of 65,535×65,535 pixels, hence up to 4 gigapixels (for an aspect ratio of 1:1). JPEG is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality.
Compact Disc Capacity Typically up to 700 MiB (up to 80 minutes audio) Read mechanism 780 nm wavelength (infrared and red edge) semiconductor laser, 1200 Kibit/s (1×) Write mechanism 1200 Kibit/s (1×)
Sampling 4 bit audio (2^4) gives us only 16 values, a far cry from 16-bit audio's 65,536! sample rate. Sample rate refers to the number of samples or measurements taken each second from a recording. The typical CD sample rate is 44.1kHz, or 44,100 samples per second.
The bit rate is quantified using the bits per second unit bit/s, often in conjunction with an SI prefix such as "kilo" (1 kbit/s = 1000 bit/s), "mega" (1 Mbit/s = 1000 kbit/s), "giga" (1 Gbit/s = 1000 Mbit/s) or "tera" (1 Tbit/s = 1000 Gbit/s). The non-standard abbreviation "bps" is often used to replace the standard symbol "bit/s", so that, for example, "1 Mbps" is used to mean one million bits per second. One byte per second (1 B/s) corresponds to 8 bit/s.
The RGB565 color format is the same as the RGB555 color format, except that 6 bits are used for the green value instead of 5. Therefore, all 16 bits are in use. The organization of the pixels in the image buffer is from left to right and bottom up. RGB888 --> 24-bit RGB (888)
Statistics Lecture One, 02.01.16
Primary Material: Course Homepage: http://www.cs.ioc.ee/ITKStat e-Book: http://onlinestatbook.com/Online_Statistics_Education.pdf
Primary Software R: https://www.r-project.org/
Introduction to Statistics Descriptive statistics are used for presenting, organizing and summarizing data. Inferential statistics are about drawing conclusions about a population based on data observed in a sample.
Data Analysis Process Data collection and preparation: Collect Data, prepare codebook, set up structure of data, enter data, screen data for errors Exploration of data: Descriptive statistics, graphs Analysis: Explore relationship between variables, compare groups
Python Lecture and Practicum Notes
Lecture 1
Get an idea what to do by next week. Ideas:
// 1. Pyglet,pygame or kivy for a game or simulation:
1.1. MP beat em' up
1.2. Survival space sim, use webcam for dynamic view
1.3. Planet rotation simulation
Check out
http://nehe.gamedev.net/
http://learnpythonthehardway.org/
// 2. WebApp
2.1. Budget Management with a GUI
// Notes: * Set up RPi web-server * Use XMind to map the idea first * Run basic website and deploy webapp to it. * Check out RPi components and sensors. * Buy a breadboard. * Check out Notepad++
Web App Programming Lecture and Practicum Notes
database: MySQL -- hosts data, indexed php: Generates html, server side language Apache: reads php files and over excecution to PHP interpreter html: Structure and contents of the web page, (dom-tree) css: styling information javascript: client side programming, interacts with html ubuntu: hosts the programs ( packetization, tcp segmentation )
HTTP requests node.js -- php ngix -- apache nchan
http sockets, streaming push module WAMP for Windows
http://enos.itcollege.ee/phpmyadmin/ PHP and APACHE is there
http://enos.itcollege.ee/~ksaareme to see changes
W3C validation https://validator.w3.org/
Node.js
Stuff about node.js.
