Video - A Practical Guide to Video and Audio Compression - page 113

control and transfer of DV material to and from compatible equipment. So the standards
are used cooperatively with one another but are independent.

5.12.4 Amateur Video Formats

If you are dealing with legacy material, a lot of footage will be recorded on VHS or beta-
max. You are going to experience some significant quality issues with the compression
when it is applied to video that has been taken off a VHS tape.
In ascending order of quality, these home video formats are grouped like this:

VHS—Long Play

●

S-VHS—Long Play

●

VHS—Short play

●

S-VHS—Short Play

●

betamax

●

5.13 Gotchas

These are the things that go bump in the night, or more likely during that rush job that you
have to deliver first thing in the morning. Video is sometimes a royal pain to encode prop-
erly. Just getting it off the tape is difficult. That is when you discover some strange noise
or artifact that causes problems. Some of these must be dealt with at source because they
are much harder to remove later.
Dot crawl is an example that is fixed by using S-video connectors that separate luma
and chroma instead of a combined composite connection.
Tracking errors are an issue to do with the quality of recording or the maintenance
of your VCR. These and other gotchas are dealt with in Chapter 31 and the chapters imme-
diately following it where the practicalities of video-compression processes are addressed.

5.14 Summary

This chapter has examined some fairly complex matters regarding video presentation.
Refer to this chapter when reading about the video-compression algorithms in Chapters
8 to 14. It will give you some insights into why the encoding technology is implemented
the way that it is.
The appendices summarize a variety of different formats and codecs for use with
video. There is a whole zoo of formats described in Appendix L.
In the next chapter we will look at digital-imaging systems. These are where film and
video converge in the same format. Most of the hard work involved with film and video
is in trying to deal with their own special properties and wrestle them into a form that fits
into a digital-imaging system.