-=> Quoting Tom Walker to Jasen Betts <=-

 -> I thought there  were more lines than that... up rpound 600 somewhere?
 -> but interlaced which could prove challenging to handle in a frame-based
 -> format like AVI...

 TW> In THEORY NTSC is 525 Lines. But in actual practice it ends up Less
 TW> than that something less then 400 avaialble for picture as I recall.

 The 525 lines includes those that are scanned during vertical
 retrace interval.  So, yes, there are actually fewer than 525
 lines for the picture itself.  If the brightness level is too
 high or if the blanking signal is defective, a viewer can see
 those retrace lines - both horizontal and vertical.

 Just dug out one of my old, old text books.  About 13 lines
 are scanned during vertical retrace each field of 262« lines.
 That's about 26 lines each frame of 525 lines, leaving about
 499 (probably somewhat less) lines for the picture.

 If I were ambitious this morning - and I'm not - I could find
 the time interval of the vertical retrace and come up with a
 more exact exact number of horizontal lines lost.

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