Introduction on Video Compression

Image and video data compression has been found to be necessary in several important applications such as visual transmission and storage. This is because, the huge amount of data involved in these and other applications, usually very much exceeds the capability of existing hardware although the technologies in related industries are growing up. Data representing information carried and the quantity of data exactly can be measured. In the context of digital image and video, data are usually measured by the number of binary units or bits. The bit rate which also known as the coding rate, is an important parameter in image and video compression and is frequently expressed in a unit of bits per pixel bpp. The term pixel is an abbreviation for picture element as is sometimes referred to as pel. In information source coding, the bit rate is sometimes expressed in a unit of bits per symbol.

2.1.2 Coding Technique

The video coding layer consists of a hybrid of temporal and spatial prediction, in conjunction with transform coding. Figure 2.1 shows a block diagram of the video coding layer for a macroblock. In summary, the picture is split into blocks. The first picture of a sequence or a random access point is typically “Intra” coded, i.e., without using information other than that contained in the picture itself. Figure 2.1 Video Coding Layer [1]

2.1.3 Video

There are many formats of video that have developed. Some common types been uses are as follows: i. Audio Video Interleave AVI format. Videos stored in the AVI format havethe extension .avi. ii. Windows Media Format WMV. Videos stored in the WMV format have the extension .wmv. iii. Moving Pictures Expert Group MPEG. Videos stored in the MPEG format have the extension .mpg or mpeg. iv. Quick Time format. Videos stored in this format have the extension .mov. v. RealVideo format. Videos stored in this format have the extension .rm or ram.