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CompTIA A+ Certification All-in-One Exam Guide

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A video is two or more separate tracks—moving picture and audio—that

each go through a compression algorithm (codec). Otherwise, the resulting

files would be huge, even for short videos. The compressed tracks then get

wrapped up into a container file, what’s often called a wrapper. When you

receive a file saved in a standard wrapper, such as .MOV for a QuickTime

Movie file, you have no way to know for certain which codecs were used to

compress the video or audio tracks inside that container file (see Figure 10-

46).

Figure 10-46 A standard container file holds multiple tracks, each encoded

separately.

Codecs Video files use standard audio codecs for the audio tracks, such as

WAV or MP3, but vary wildly in the type of video codecs used. Just as with

audio codecs, video codecs take a video stream and compress it by using

various algorithms. Here are some of the standard video codecs:

• MPEG-2 Part 2, used for DVDs, broadcast TV

• H.264, used for everything from smartphone video and streaming

video to Blu-ray movies

• H.265, half the size of h.264 at the same quality, used to support 4k

video

• VP9, Google’s competitor to h.265, used in places like Android

devices and YouTube

Wrappers When both the video and audio streams of your video file are

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