On the even frame, the CRTC displays the lines for which VLC is even. On the odd frame, the CRTC displays the lines for which VLC is odd.
In this mode, it It is necessary to reprogram the CRTC as if we were building a frame of 624 lines. The 625th line is managed automatically by the CRTC.
[[File:CRTC Interlace modes.png]]