From: Steinar H. Gunderson <sgunderson@bigfoot.com>
Date: Sun, 15 Jan 2017 10:52:10 +0000 (+0100)
Subject: Add a specification for how the official DeckLink driver stores interlaced frmaes.
X-Git-Tag: 0.5.4~2
X-Git-Url: https://git.sesse.net/?p=bmusb;a=commitdiff_plain;h=21cffe09f272f510c0a6d3e7c2fa0fff79653f30

Add a specification for how the official DeckLink driver stores interlaced frmaes.
---

diff --git a/bmusb/bmusb.h b/bmusb/bmusb.h
index 6aabd51..b61b66f 100644
--- a/bmusb/bmusb.h
+++ b/bmusb/bmusb.h
@@ -102,8 +102,10 @@ struct VideoMode {
 
 // 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.