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Codecs and Compression

Uncompressed standard-definition video’s data rate is 270 Megabits/second (about 34 Megabytes/second); 1080i60 HDTV runs at 1.2 Gigabits/second (150 Megabytes/second). That’s a lot of bits, so many video formats—both on tape and inside your Mac—use compression to get the data rate down to something more manageable. A codec is the bit of software and/or hardware that manages this task; “codec” is short for COmpressor/DECompressor.

Of course, there are tape formats and capture cards to record and play back uncompressed video, too; we still refer to part of the system that records and retrieves the bits from disk as a codec, hiding our terminological imprecision with the dodgy excuse that in these cases, “codec” stands for COder/DECoder.


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