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

[bmusb] / bmusb / bmusb.h

diff --git a/bmusb/bmusb.h b/bmusb/bmusb.h
index f4af6aa14b2a1399168d3f75673b1d2215846770..b61b66f2e2e9e59b72b3ba42faddcbcb611cfbb8 100644 (file)
--- a/bmusb/bmusb.h
+++ b/bmusb/bmusb.h
@@ -4,6 +4,7 @@
 #include <libusb.h>
 #include <stdint.h>
 #include <atomic>
+#include <chrono>
 #include <condition_variable>
 #include <deque>
 #include <functional>
@@ -39,6 +40,14 @@ class FrameAllocator {
                // If so, <len> and <size> are still about the number of total bytes
                // so if size == 1024, there's 512 bytes in data and 512 in data2.
                bool interleaved = false;
+
+               // At what point this frame was received. Note that this marks the
+               // _end_ of the frame being received, not the beginning.
+               // Thus, if you want to measure latency, you'll also need to include
+               // the time the frame actually took to transfer (usually 1/fps,
+               // ie., the frames are typically transferred in real time).
+               std::chrono::steady_clock::time_point received_timestamp =
+                       std::chrono::steady_clock::time_point::min();
        };
 
        virtual ~FrameAllocator();
@@ -93,8 +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.