A film that would fill your phone
A two hour film in raw form takes hundreds of gigabytes. Yet you stream one on a phone in minutes.
Something squeezes the film for the trip and opens it again at the end. That something is a codec.
By the end of this lesson
Note
I can say what a codec does and choose lossy or lossless for a job.
Key words
| Word | What it means |
|---|---|
| Bandwidth | the most data a link can carry each second |
| Codec | a tool that compresses and uncompresses sound or video |
| Compress | make a file smaller |
| Uncompress | turn a small file back into playable data |
| Lossy | compression that throws some detail away for good |
| Lossless | compression that keeps every detail |
| Algorithm | the steps a program follows to do a job |
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A codec squeezes and opens
The word codec comes from coder and decoder. It does two jobs.
To compress is to make data smaller before it is sent or saved. To uncompress is to turn it back into playable sound or picture at the other end.
Smaller files save space and need less bandwidth.
Lossy and lossless
Lossless compression keeps every detail. When you uncompress the file you get back exactly what you put in. The file is smaller but not tiny.
Lossy compression throws some detail away for ever. It aims to drop what people hardly notice. The file gets much smaller.
Three codecs to know
| Codec | For | Type | How it saves space |
|---|---|---|---|
| MPEG-4 | Video | Mostly lossy. Some parts are lossless. | Stores only what changes between frames |
| MP3 | Audio | Lossy | Drops sounds the ear can barely hear |
| FLAC | Audio | Lossless | Finds patterns and stores them in fewer bits |
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3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.