From 2c1faeb15715794525f48110c2b8a9df96b387c1 Mon Sep 17 00:00:00 2001
From: Carl Hetherington <cth@carlh.net>
Date: Mon, 15 Mar 2021 01:36:51 +0100
Subject: Fix various bugs in subtitle/ccap verification.

Check that subtitles don't overlap reel boundaries, and fix a few
tests that trip this check.

Fix confusion when calculating subtitle timings during verification
where the picture asset frame rate was being used rather than the
subtitle asset's edit rate.

Do the subtitle timing verification for Interop as well as SMPTE
subtitles.

Take <StartTime> tags into account when checking subtitles, even
though Bv2.1 says they should be set to 0.

Rename Time::as_editable_units to Time::as_editable_units_ceil
and add a _floor variant, then use that to round down when checking
reel boundary overlaps.
---
 src/verify.cc | 76 +++++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 53 insertions(+), 23 deletions(-)

(limited to 'src/verify.cc')

diff --git a/src/verify.cc b/src/verify.cc
index bddf1683..97758e61 100644
--- a/src/verify.cc
+++ b/src/verify.cc
@@ -763,7 +763,7 @@ static
 void
 verify_text_timing (
 	vector<shared_ptr<Reel>> reels,
-	optional<int> picture_frame_rate,
+	int edit_rate,
 	vector<VerificationNote>& notes,
 	std::function<bool (shared_ptr<Reel>)> check,
 	std::function<string (shared_ptr<Reel>)> xml,
@@ -775,32 +775,39 @@ verify_text_timing (
 	auto too_short = false;
 	auto too_close = false;
 	auto too_early = false;
+	auto reel_overlap = false;
 	/* current reel start time (in editable units) */
 	int64_t reel_offset = 0;
 
-	std::function<void (cxml::ConstNodePtr, int, int, bool)> parse;
-	parse = [&parse, &last_out, &too_short, &too_close, &too_early, &reel_offset](cxml::ConstNodePtr node, int tcr, int pfr, bool first_reel) {
+	std::function<void (cxml::ConstNodePtr, optional<int>, optional<Time>, int, bool)> parse;
+	parse = [&parse, &last_out, &too_short, &too_close, &too_early, &reel_offset](cxml::ConstNodePtr node, optional<int> tcr, optional<Time> start_time, int er, bool first_reel) {
 		if (node->name() == "Subtitle") {
 			Time in (node->string_attribute("TimeIn"), tcr);
+			if (start_time) {
+				in -= *start_time;
+			}
 			Time out (node->string_attribute("TimeOut"), tcr);
-			if (first_reel && in < Time(0, 0, 4, 0, tcr)) {
+			if (start_time) {
+				out -= *start_time;
+			}
+			if (first_reel && tcr && in < Time(0, 0, 4, 0, *tcr)) {
 				too_early = true;
 			}
 			auto length = out - in;
-			if (length.as_editable_units(pfr) < 15) {
+			if (length.as_editable_units_ceil(er) < 15) {
 				too_short = true;
 			}
 			if (last_out) {
 				/* XXX: this feels dubious - is it really what Bv2.1 means? */
-				auto distance = reel_offset + in.as_editable_units(pfr) - *last_out;
+				auto distance = reel_offset + in.as_editable_units_ceil(er) - *last_out;
 				if (distance >= 0 && distance < 2) {
 					too_close = true;
 				}
 			}
-			last_out = reel_offset + out.as_editable_units(pfr);
+			last_out = reel_offset + out.as_editable_units_floor(er);
 		} else {
 			for (auto i: node->node_children()) {
-				parse(i, tcr, pfr, first_reel);
+				parse(i, tcr, start_time, er, first_reel);
 			}
 		}
 	};
@@ -814,11 +821,31 @@ verify_text_timing (
 		 * read in by libdcp's parser.
 		 */
 
-		auto doc = make_shared<cxml::Document>("SubtitleReel");
-		doc->read_string (xml(reels[i]));
-		auto const tcr = doc->number_child<int>("TimeCodeRate");
-		parse (doc, tcr, picture_frame_rate.get_value_or(24), i == 0);
-		reel_offset += duration(reels[i]);
+		shared_ptr<cxml::Document> doc;
+		optional<int> tcr;
+		optional<Time> start_time;
+		try {
+			doc = make_shared<cxml::Document>("SubtitleReel");
+			doc->read_string (xml(reels[i]));
+			tcr = doc->number_child<int>("TimeCodeRate");
+			auto start_time_string = doc->optional_string_child("StartTime");
+			if (start_time_string) {
+				start_time = Time(*start_time_string, tcr);
+			}
+		} catch (...) {
+			doc = make_shared<cxml::Document>("DCSubtitle");
+			doc->read_string (xml(reels[i]));
+		}
+		parse (doc, tcr, start_time, edit_rate, i == 0);
+		auto end = reel_offset + duration(reels[i]);
+		if (last_out && *last_out > end) {
+			reel_overlap = true;
+		}
+		reel_offset = end;
+	}
+
+	if (last_out && *last_out > reel_offset) {
+		reel_overlap = true;
 	}
 
 	if (too_early) {
@@ -838,6 +865,12 @@ verify_text_timing (
 			VerificationNote::Type::WARNING, VerificationNote::Code::INVALID_SUBTITLE_SPACING
 		});
 	}
+
+	if (reel_overlap) {
+		notes.push_back ({
+			VerificationNote::Type::ERROR, VerificationNote::Code::SUBTITLE_OVERLAPS_REEL_BOUNDARY
+		});
+	}
 }
 
 
@@ -948,13 +981,8 @@ verify_text_timing (vector<shared_ptr<Reel>> reels, vector<VerificationNote>& no
 		return;
 	}
 
-	optional<int> picture_frame_rate;
-	if (reels[0]->main_picture()) {
-		picture_frame_rate = reels[0]->main_picture()->frame_rate().numerator;
-	}
-
 	if (reels[0]->main_subtitle()) {
-		verify_text_timing (reels, picture_frame_rate, notes,
+		verify_text_timing (reels, reels[0]->main_subtitle()->edit_rate().numerator, notes,
 			[](shared_ptr<Reel> reel) {
 				return static_cast<bool>(reel->main_subtitle());
 			},
@@ -968,7 +996,7 @@ verify_text_timing (vector<shared_ptr<Reel>> reels, vector<VerificationNote>& no
 	}
 
 	for (auto i = 0U; i < reels[0]->closed_captions().size(); ++i) {
-		verify_text_timing (reels, picture_frame_rate, notes,
+		verify_text_timing (reels, reels[0]->closed_captions()[i]->edit_rate().numerator, notes,
 			[i](shared_ptr<Reel> reel) {
 				return i < reel->closed_captions().size();
 			},
@@ -1262,6 +1290,8 @@ dcp::verify (
 				most_closed_captions = std::max (most_closed_captions, reel->closed_captions().size());
 			}
 
+			verify_text_timing (cpl->reels(), notes);
+
 			if (dcp->standard() == Standard::SMPTE) {
 
 				if (have_main_subtitle && have_no_main_subtitle) {
@@ -1292,14 +1322,12 @@ dcp::verify (
 				if (lfoc == markers_seen.end()) {
 					notes.push_back ({VerificationNote::Type::WARNING, VerificationNote::Code::MISSING_LFOC});
 				} else {
-					auto lfoc_time = lfoc->second.as_editable_units(lfoc->second.tcr);
+					auto lfoc_time = lfoc->second.as_editable_units_ceil(lfoc->second.tcr);
 					if (lfoc_time != (cpl->reels().back()->duration() - 1)) {
 						notes.push_back ({VerificationNote::Type::WARNING, VerificationNote::Code::INCORRECT_LFOC, raw_convert<string>(lfoc_time)});
 					}
 				}
 
-				verify_text_timing (cpl->reels(), notes);
-
 				LinesCharactersResult result;
 				for (auto reel: cpl->reels()) {
 					if (reel->main_subtitle() && reel->main_subtitle()->asset()) {
@@ -1458,6 +1486,8 @@ dcp::note_to_string (VerificationNote note)
 		return "At least one subtitle lasts less than 15 frames.";
 	case VerificationNote::Code::INVALID_SUBTITLE_SPACING:
 		return "At least one pair of subtitles is separated by less than 2 frames.";
+	case VerificationNote::Code::SUBTITLE_OVERLAPS_REEL_BOUNDARY:
+		return "At least one subtitle extends outside of its reel.";
 	case VerificationNote::Code::INVALID_SUBTITLE_LINE_COUNT:
 		return "There are more than 3 subtitle lines in at least one place in the DCP.";
 	case VerificationNote::Code::NEARLY_INVALID_SUBTITLE_LINE_LENGTH:
-- 
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