CTS-D Certified Technology Specialist-Design Exam Guide by Brad Grimes

Author:Brad Grimes
Language: eng
Format: epub
ISBN: 0071835695
Publisher: McGraw Hill LLC
Published: 2016-08-15T00:00:00+00:00

NOTE 4:2:0 sampling is also a common choice. It is mathematically the same as 4:1:1 sampling in terms of required bandwidth, with basically the same color resolution and a different pixel pattern. Both 4:2:0 and 4:1:1 sampling suffers from blocky color patterns and poor color fidelity.

Bandwidth: Determining Total Program Size

When determining the total required bandwidth of an AV stream, it’s important to remember that reducing or increasing the video or audio information changes the total data transmission rate. Yes, video requires a lot of bandwidth, but sometimes people forget the audio. Audio can require a lot more bandwidth than you might think, especially for surround-sound applications. All those channels add up. Remember also to account for overhead, namely, the addressing and control information that must accompany AV packets.

When it comes to AV program bandwidth, here is the formula:

Video bit rate + Audio bit rate + Overhead = Total required bandwidth (bps)

Once AV program bandwidth is calculated, you may find that you must choose a lower sampling rate to fit within the bandwidth limitations of your overall system. You don’t necessarily have to think of choosing a lower sampling rate as sacrificing quality, though, especially when it comes to video.

Digital techniques have become far more sophisticated in recent years. Modern digital codecs can analyze image content and decide how to prioritize that detail with greater ease. With a color subsampled image, the program decoding the picture estimates the missing pixel values, uses the surrounding intact color values, and provides the link between the two. That means a 4:2:2 image can look almost as good as a 4:4:4.

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