user23697: I've been learning about the blanking intervals in video signals and often see diagrams like this:

(Ref)
But, I often also see the blanking regions describes as being on both sides of the image:

(Ref)
Which is correct? I would have thought the latter as I would have thought for CRTs the electron beam would be blanked at the end of a line so it can return to the start of the next line and then un-blanked. Same for vertical.
Which image/description is correct?

user14523: They are both right, depending on the context and level of detail. The latter accurately describes what happens within the waveform. If you look further down in your reference, it shows that there is a "front porch" and "back porch" of the horizontal and vertical intervals.
However, the former describes what happens practically, especially in terms of the useful parts of the vertical blanking interval (VBI). Closed captioning, teletext, VITS, VITC, AMOL all use the blanked lines at the top of the field to transmit their data. (You should also note that your reference intentionally chose this layout in order to draw parallels with digital VANC and HANC, which are only at the top and left of the picture.)

23697: <p>I've been learning about the blanking intervals in video signals and often see diagrams like this:</p>

<p><a href="https://i.stack.imgur.com/um2oE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/um2oE.png" alt="Shows vertical and horizontal blanking portions of image"></a>
<a href="http://www.sbe24.org/wba-sbe-shows/archives/Clinic2009/Conrad-Harris-2009.pdf" rel="nofollow noreferrer">(Ref)</a></p>

<p>But, I often also see the blanking regions describes as being on both sides of the image:</p>

<p><a href="https://i.stack.imgur.com/zDZ8Z.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/zDZ8Z.png" alt="Shows vertical and horizontal blanking portions of image"></a>
<a href="http://csweb.cs.wfu.edu/~torgerse/Kokua/Irix_6.5.21_doc_cd/usr/share/Insight/library/SGI_bookshelves/SGI_Developer/books/VFC_PG/sgi_html/ch03.html" rel="nofollow noreferrer">(Ref)</a></p>

<p>Which is correct? I would have thought the latter as I would have thought for CRTs the electron beam would be blanked at the end of a line so it can return to the start of the next line and then un-blanked. Same for vertical.</p>

<p>Which image/description is correct?</p>
 14523: <p>They are both right, depending on the context and level of detail. The latter accurately describes what happens within the waveform. If you look further down in your reference, it shows that there is a "front porch" and "back porch" of the horizontal and vertical intervals.</p>

<p>However, the former describes what happens practically, especially in terms of the useful parts of the vertical blanking interval (VBI). Closed captioning, teletext, VITS, VITC, AMOL all use the blanked lines at the top of the field to transmit their data. (You should also note that your reference intentionally chose this layout in order to draw parallels with digital VANC and HANC, which are only at the top and left of the picture.)</p>
