Multimedia (マルチメディア) means handling different kinds of information, such as text, sound, still images and video, together as digital data.
Multimedia
Text
Sound
Still images
Video
Inside a computer, every kind of information is represented as data made of 0s and 1s, so it can all be combined within a single work or screen. An e-book textbook with narrated audio or explanatory videos is a familiar example.
AnalogyLike a set meal with the main dish, side dish and soup on one tray, it serves information of different natures together as one work.
How to remember"Multi" means many, and "media" is the plural of medium, so the word literally says "many media".
Exam points
ExamSoftware for arranging materials such as text, images and sound and finishing them into a single work is called authoring software (オーサリングソフト).
Web content (Webコンテンツ) is the substance of the information, such as text, images, sound and video, that is published on a website and viewed in a browser.
Web pages are written in HTML, a language that describes the structure of a document, and image and video files are embedded in them to display as a single page. That makes Web content one of the most familiar ways multimedia reaches users.
AnalogyCompared to a magazine, the website is the magazine itself, and the Web content is the articles and photos printed on its pages.
How to rememberContent means what is held inside something, so read it as whatever fills the container called the Web.
Exam points
Mix-upA font whose character widths vary is a proportional font (プロポーショナルフォント), and one in which every character has the same width is a monospaced font (等幅フォント).
Hypermedia (ハイパーメディア) is a mechanism that attaches links (references to other information) not only to text but also to images, sound and video, so users can follow them to related information.
It grew out of the idea of hypertext, which connects words and phrases within documents by links. Instead of reading in a fixed order as with a paper book, users choose their own path, and the Web is an example that put this mechanism into wide use.
AnalogyLike a rail map, you can follow a line from any station to another, and the rider decides the order of the stops.
How to remember"Hyper" means beyond: you can jump beyond the order of the pages.
Exam points
ExamHypertext (ハイパーテキスト) lets you move to related information from links embedded throughout a document, and extending those link targets to images and sound gives hypermedia (ハイパーメディア).
Encoding (エンコード) converts data into another form of representation, a code, according to set rules; in Japanese it is also called 符号化.
When audio or video is encoded, compression, which reduces the amount of data, is usually done at the same time, shrinking the space needed to store or send it. For example, turning a voice recording into an MP3 file is encoding.
AnalogyIt is like folding your belongings in a set way and packing them into boxes for a move: they become easier to carry, but you cannot use them as they are.
How to rememberThe prefix en- means "put into", so encoding puts data into a code.
Exam points
Mix-upEncryption (暗号化) aims to keep third parties from reading the content, and undoing it requires a key. Encoded (エンコード) data can be returned to its original form without any key, simply by following the format's rules.
Decoding (デコード) returns encoded data to its original form so it can be played or displayed; in Japanese it is also called 復号, though in cryptography the same word means decryption, a different process.
Original data
Encode (convert, compress)
Store or send
Decode (back to the original form)
Play or display
The restored data is used to play sound or show pictures on the screen.
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Decoding compressed data also involves decompression, which expands the shrunken data back to a playable size. A video player app decodes the data it receives before showing it on screen, and the software or device that handles encoding and decoding is called a codec.
AnalogyIt is like unpacking the folded belongings at your new home and laying them out so they are ready to use.
How to rememberThe prefix de- means "remove" or "reverse", so decoding takes data back out of its code.
Exam points
Mix-upCompression can be lossless (可逆圧縮), restoring the original data exactly when decompressed, or lossy (非可逆圧縮), discarding some information to cut the size sharply.
Streaming (ストリーミング) is a delivery method that plays audio or video data in order from the parts already received while the rest is still arriving.
Sender sends in small pieces
Receiver holds a little
Play from what is held
Receive the rest while playing
While it plays, more data keeps arriving and refills the stored portion.
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Because playback can begin from whatever has arrived, even a long video can be watched without waiting for all of it. To keep playback from stalling, the receiver temporarily holds data a little ahead of what is playing, and this storage area is called a buffer.
AnalogyLike conveyor-belt sushi, you do not wait for every plate to arrive; you eat each one as it comes around.
How to rememberA stream is a small river, and the name comes from data flowing in continuously like running water.
Exam points
ExamStreaming (ストリーミング) can begin playback as soon as part of the data arrives. That is where it differs from the download method (ダウンロード方式), which plays only after the entire file has arrived.
DRM (digital rights management) is an umbrella term for mechanisms that use technology to prevent unauthorized copying of digital content or use beyond agreed limits, protecting the rights of copyright holders.
DRM (umbrella term)
Examples of protection means
Encrypting content
Limiting playback devices
Limiting viewing period and copy count
Examples of specific methods
CPRM (for recording media)
Digital data can be copied any number of times without degrading, so music, video and e-books delivered online often rely on technical protection. Specific means include encrypting the content, limiting which devices can play it, and restricting viewing periods or copy counts, and each method has its own name.
AnalogyLike a rental meeting room with a lock, only the person who booked it can get in, and only during the booked time; otherwise the door stays shut.
How to rememberIt stands for Digital Rights Management: managing (M) the rights (R) to digital works.
Exam points
ExamDRM is not the name of one method but a collective name for methods that use technology to restrict how digital content is copied, played and otherwise used, so as to protect its copyright holders.
CPRM is a copyright protection technology used on writable recording media that controls how many times content can be copied.
Some digital broadcast programs carry copy conditions, such as "may be recorded only once" (copy-once), and CPRM-compatible devices and media honor that condition when recording. The recorded content is encrypted, so devices without CPRM support cannot play it.
AnalogyLike a punch card good for a set number of rides, the uses are fixed in advance, and once they run out the card is done.
How to rememberIt stands for Content Protection for Recordable Media, and the RM at the end shows that its target is recording media.
Exam points
ExamCPRM is a copyright protection technology for recording media that, for example, ensures content permitted to be copied only once is recorded in line with that condition.