It can be placed in any place in the path of the video signal. The VITS generator is configurable. Lines can cross the VITS generator without modification, others are erased and recreated in the VITS generator.
http://perso.orange.fr/jf.fourcadier/television/lignes_test/lignes_test_e.htm
This simple adapter can be used to convert Y/C video (S-video) to a composite video. This adapter is useful in cases where your video output device has only S-video output but your signal source accepts only composite video input. This circuit works with both PAL and NTSC video standards.
http://www.tkk.fi/Misc/Electronics/circuits/svideo2cvideo.html
Build a miniature short-range wireless video system with off-the-shelf parts. The video modulator provides a simple method for interfacing the video signal to a standard TV. Transmission distance is limited to a few feet.
http://www.solorb.com/elect/video/microvid/index.html
When I made FM radio, I could hear the voice signal of first channel of TV. On the frequency slightly lower than that, I could hear the noisy signal of picture of TV. My oscilloscope has Z input. It can display black and white. I made the simple TV receiver. It displays the picture on my oscilloscope.
http://www.intio.or.jp/jf10zl/tv.htm
it is based in three transistor. With this circuit we can amplification selectively the high signal of picture frequencies [Video] with result bigger clarity than this.
http://users.otenet.gr/~athsam/video_signal_emphasis.htm
http://www.web-ee.com/Electronic-Projects/projects/video_stab/index.shtml
for ATV application
http://f1buy.club.fr/realisations/emetteur23/videopic.html