Before Encoding: Video Acquisition Chain and Video Quality

With real world video, we have either digital or analog feeds.With digital feeds, we would be looking at transcoding (format conversion) or transrating (bitrate conversion) methods in the digital domain for bitrate reduction only, but with analog feeds such as analog TV or cameras, the video acquisition chain becomes more complex.

Before we go further to analyze the digital encoding issues, let’s take a step back and examine the analog side of the video acquisition.

The typical single channel video acquisition chain is as follows:

The audio acquisition section receives less attention today, I believe this to be primarily because the audio problem is technically solved sufficiently at a low enough cost that it ceases to be a technical concern beyond BOM (bill of materials) costs and feature integration. The video section however is where a lot of engineering resources are spent.

Because this is an analog feed in a digital system, there are multiple sources of noise that can impact capture quality. Below is a partial list of various descriptions of video quality issues and methods to solve them.

As is evident, to build a good analog video acquisition and compression subsystem, one has to solve a variety of problems, and the weaker the potential signal feed may be, the more complete the noise reduction strategy has to be taking into consideration the application of most of the above solutions.

It is also important to note that when the video feed is external to an s/video port, most of these noise issues are not a concern.

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