// Represents the format of an actual frame coming in.
// Note: Frame rate is _frame_ rate, not field rate. So 1080i60 gets 30/1, _not_ 60/1.
-// "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
+// "second_field_start" is only valid for interlaced modes. If it is 1,
+// the two fields are actually stored interlaced (ie., every other line).
+// If not, each field is stored consecutively, and 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).
struct VideoFormat {
uint16_t id = 0; // For debugging/logging only.