Canon XF300 User Manual download pdf (Page 9)

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CODECS AND FILE FORMATS

An image is compressed for recording/storage and decompressed for

display. This process is also referred to as “encoding” and “decoding”.

Codec is an abbreviation that stands for Compressor/Decompressor or

Coder/Decoder, meaning it can both encode and decode something,

in this case video.

Codecs are usually designed for speci c purposes. Some codecs

are designed for acquisition, others are meant speci cally for editing,

and then some codecs are intended primarily for transmission. For

example, XF series cameras acquire video footage and encode them to

recording media using the Canon XF MPEG-2 4:2:2 codec. This codec

has been optimized to edit natively on most non-linear editing (NLE)

systems and can be used as an editing codec without the need for

transcoding. If a  nal product is designated for a transmission medium

such as broadcast, DVD or Blu-Ray disk or the internet, it will be

exported to the codec appropriate for that distribution medium.

MPEG-2, 4:2:2, 50Mbps codec

MPEG-2 is a professional compression format widely supported by

hardware and software manufacturers. It is also less hardware-

intensive than other available compression formats.

MPEG-2 compression takes advantage of the redundancy between

successive frames of video, which often contain similar picture

information, even when the image has moved slightly from one frame

to the next.

Because the human visual system is less sensitive to the position and

motion of color than luminance, storing more luminance detail than

color detail can optimize bandwidth. This process is known as chroma

subsampling and is represented by a three-part ratio separated by

colons. The  rst number refers to the width of a conceptual region of

luminance, with the following two numbers indicating the number of

chrominance samples. For example the 4:2:2 scheme requires

two-thirds the bandwidth of 4:4:4 while resulting in almost no visual

di erence as perceived by the viewer.

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Canon XF300 User Manual Page 9