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file size

The file size represents the amount of bits and bytes of a file. It depends exclusively on the type of information - text, graphic, photo, audio, video - and whether it has been subjected to compression. The file size is easy to calculate and determines the amount of memory required. Depending on the type of information, it can be a few kilobytes, megabytes or even gigabytes.

The file sizes of different media

Texts have the smallest file sizes. The size roughly corresponds to the number of characters. If a page of text has 30 lines of 40 characters each, then the file size is 1,200 bytes or 1.2 kilobytes( KB).

For graphics, images and photos in pixel graphics, the file size is calculated from the number of pixels and the color depth. For the VGA format with 640 x 480 pixels and a color depth of 4 bits, the file size is 153.6 KB, which increases to 480 KB in the case of Super VGA( SVGA). High- resolution graphics in QUXGA with a screen resolution of 3,200 x 2,400 pixels and a color depth of 24 bits result in a file size of 23.04 megabytes( MB).

File sizes of audio and video

Audio files are even larger, and their size depends to a large extent on the quantization. At low quality, as used in ISDN, a quantization of 8 bits and a sampling frequency of 8 kHz result in a file size of 8 KB/s. The situation is quite different for high sound quality. The situation is quite different for high sound quality, as required in compact discs( CD) and DVDs. For example, a DVD uses a sampling depth of 16 bits at a sampling rate of 44.1 kHz. The resulting data volume amounts to 88.2 KB in one second. With increased sound quality in stereophony, a sampling depth of 24 bits and a sampling frequency of 196 kHz then add up to 1.176 MB in one second.

Moving images have an even larger data volume. This is calculated from the data of a single frame and the frame rate. For the PAL television standard with 625 lines, 25 full frames and an aspect ratio of 4:3, a color depth of 24 bits results in a file size of 39 MB in one second.

Since all values were determined without data reduction or color subsampling, these data volumes also show the necessity of using compression methods and other techniques to reduce these data volumes.

Englisch: file size
Updated at: 08.11.2013
#Words: 385
Links: file, information, text (TXT), photo, audio
Translations: DE

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