Taewon's road not taken

HLS

- stable media format, it has been out for more than ten years.

- suuports its own DRM only

DASH 

- can deliver low latency

- uses templated manifest that can be cached

- DASH supports range of encryption solutions

https://coding-factory.tistory.com/411

https://m.blog.naver.com/wiseyoun07/220275811188

https://m.blog.naver.com/PostView.nhn?blogId=wiseyoun07&logNo=220259992314&proxyReferer=https%3A%2F%2Fwww.google.com%2F

https://m.blog.naver.com/PostView.nhn?blogId=htech79&logNo=221148900796&categoryNo=1&proxyReferer=https%3A%2F%2Fwww.google.com%2F

CDN - a content delivery network is a system of geographically distributed servers used to transport media files. The purpose of the CDN is to host live streaming videos to users. CDN works like amazon warehouse. If closest edge server does have resource cached, it will deliver it to the user. If not, it will deliver the media by requesting to another network. (Think of it like globally connected highways for data).

Advantage of CDNS - scalability, speed, quality and security.

When CDNs are not needed - Small audience, limited budget. 

Every year people are abandoning traditional satellite and cable services and switching to live streaming.(favoring towards netflix over broadbands).

.ts, .mp4, there are various media formats and it can be bothersome and burden towards memory to have all these different formats available for end users. So came up with the solution of cmaf, making a universal media format for all media content. 

CMAF also provides low latency, by dividing original media file into small pieces called chunks. 

1. syntax errors that prevent a program from running
2. runtime errors when code fails to execute or has unexpected behavior
3. semantic (or logical) errors when code doesn't do what it's meant to.

appname/main/java - holds java files 

appname/main/res/layout - screen layout xmls

appname/main/res/values - style xmls

Create another screen - 

New -> Activity -> empty activity

Add xmlns:tools="http://schemas.android.com/tools"

tools:context=".CheatActivity">

How to start another activity

startActivity(intent);

Intent는 컴포넌트가 운영체제와 통신하기 위해 사용할 수 있는 객체다.

Intent i = new Intent(QuizActivity.this, CheatActivity.class);

인텐드 인스턴스를 선언하면서 두개의 클래스들을 메니페스트(AndroidManifest.xml)에 선언해주어야 하는 이유다. 

intent.putExtra(String, 값);

----

startActivity는 값을 다시 못 받는다. 

startActivityForResult(Intent, int)는 결과를 돌려받는 메소드다. 

시작은 startActivityForResult,,  끝은 onActivityResult()

안드로이드는 애플리케이션을 실행시키는 것이 아닌 액티비티를 실행시켜준다. 

액티비티들은 스택구조 형식으로 실행이된다. 

ExpressionDescription

[ㄱ-ㅎㅏ-ㅣ가-힣] = 한글 포함

+ = at least one

* = zero or more

 var str = "Hellooo World! Hello W3Schools!"; 
  var patt1 = /lo*/g;
  var result = str.match(patt1);

l,looo,l,l,lo,l

? = The n? quantifier matches any string that contains zero or one occurrences of n.

var str = "1, 100 or 1000?";
var patt1 = /10?/g;

1,10,10

https://medium.com/techsuzu/android-push-notification-using-fcm-firebase-cloud-messaging-c37d165b8320

Start : https://firebase.google.com/?authuser=0

add the following : 

classpath 'com.google.gms:google-services:4.0.1'

apply plugin: 'com.google.gms.google-services'

implementation 'com.google.firebase:firebase-messaging:17.3.4'
implementation 'com.google.android.gms:play-services-auth:16.0.1'

Regular expressions are used in programming languages to match parts of strings. You create patterns to help you do that matching.

QuantifierDescription

MetacharacterDescription

1. .test()

var str = "Hello world";

var testing = /world/;

testing.test(str); //outputs true

can add | for multiple search

let petString = "James has a pet cat.";

let petRegex = /dog|cat|bird|fish/; // Change this line

let result = petRegex.test(petString);

add i on the back to ignore upperlower case

let myString = "freeCodeCamp";

let fccRegex = /freecodecamp/i; // Change this line

let result = fccRegex.test(myString);

2. .match()

extracts the string

add g on the back for multiple results

To search or extract a pattern more than once, you can use the g flag.

let repeatRegex = /Repeat/g;

testStr.match(repeatRegex);

// Returns ["Repeat", "Repeat", "Repeat"]

The wildcard character . will match any one character. 

[] Character classes allow you to define a group of characters you wish to match by placing them inside square ([ and ]) brackets.

Inside a character set, you can define a range of characters to match using a hyphen character: -.

To create a negated character set, you place a caret character (^) after the opening bracket and before the characters you do not want to match.

For example, /[^aeiou]/gi matches all characters that are not a vowel. Note that characters like ., !, [, @, / and white space are matched - the negated vowel character set only excludes the vowel characters.

+ to look for a character one or more time

* to look for a character zero or more time

In an earlier challenge, you used the caret character (^) inside a character set to create a negated character set in the form [^thingsThatWillNotBeMatched]. Outside of a character set, the caret is used to search for patterns at the beginning of strings.

You can search the end of strings using the dollar sign character $ at the end of the regex.

The closest character class in JavaScript to match the alphabet is \w. This shortcut is equal to [A-Za-z0-9_]. This character class matches upper and lowercase letters plus numbers. Note, this character class also includes the underscore character (_).

\w = a-zA-Z0-9

\W = not \w

\d = 0-9

\D = not digit

problem 1:

1) Usernames can only use alpha-numeric characters.

2) The only numbers in the username have to be at the end. There can be zero or more of them at the end.

3) Username letters can be lowercase and uppercase.

4) Usernames have to be at least two characters long. A two-character username can only use alphabet letters as characters.

let username = "JackOfAllTrades";

let userCheck = /^[a-z]([0-9]{2,}|[a-z]+\d*)$/i; // Change this line

let result = userCheck.test(username);

1. ^ - start of input
2. [a-z] - first character is a letter
3. [0-9]{2,0} - ends with two or more numbers
4. | - or
5. [a-z]+ - has one or more letters next
6. \d* - and ends with zero or more numbers
7. $ - end of input
8. i - ignore case of input

------

to match only the string "hah" with the letter a appearing at least 3 times, your regex would be /ha{3,}h/.

t{3,6} = 3 to 6 

t{3,} = 3 or more

t{3} = 3

? = zero or more

A positive lookahead will look to make sure the element in the search pattern is there, but won't actually match it. A positive lookahead is used as (?=...) where the ... is the required part that is not matched.

On the other hand, a negative lookahead will look to make sure the element in the search pattern is not there. A negative lookahead is used as (?!...) where the ... is the pattern that you do not want to be there. The rest of the pattern is returned if the negative lookahead part is not present.

remove white spaces

let regex = /^\s+|\s+$/g;

str.replace(regex, "");