-// TODO: Add another extra_lines_ parameter for interlaced.
-bool decode_video_format(uint16_t video_format, unsigned *width, unsigned *height, unsigned *extra_lines_top, unsigned *extra_lines_bottom,
+// "second_field_start" is only valid for interlaced modes; it signifies
+// how many lines from the very top of the frame there are before the second field
+// starts (so it will always be >= height/2 + extra_lines_top).
+bool decode_video_format(uint16_t video_format, unsigned *width, unsigned *height, unsigned *second_field_start,
+ unsigned *extra_lines_top, unsigned *extra_lines_bottom,