Allow a fudge factor when checking for gaps/overlaps between segments

Sometimes in the wild (particularly on youtube) segments may not be timed perfectly, so allow up to 10ms of gap or overlap
to be counted as "equal" for purposes of finding the best segment.

common/common/segments.py

@@ -151,6 +151,11 @@ def get_best_segments(hours_path, start, end, allow_holes=True):
 	# python's datetime types represent these as integer microseconds internally. So the parsing
 	# to these types is exact, and all operations on them are exact, so all operations are exact.
 
+	# ...however in the wild we sometimes see timestamps or durations that differ by a few ms.
+	# So we allow some fudge factors.
+	ALLOWABLE_OVERLAP = 0.01 # 10ms
+	ALLOWABLE_GAP = 0.01 # 10ms
+
 	result = []
 
 	for hour in hour_paths_for_range(hours_path, start, end):
@@ -182,13 +187,14 @@ def get_best_segments(hours_path, start, end, allow_holes=True):
 			else:
 				# normal case: check against previous segment end time
 				prev_end = result[-1].end
-				if segment.start < prev_end:
+				gap = (segment.start - prev_end).total_seconds()
+				if gap < -ALLOWABLE_OVERLAP:
 					# Overlap! This shouldn't happen, though it might be possible due to weirdness
 					# if the stream drops then starts again quickly. We simply ignore the overlapping
 					# segment and let the algorithm continue.
 					logging.info("Overlapping segments: {} overlaps end of {}".format(segment, result[-1]))
 					continue
-				if result[-1].is_partial or prev_end < segment.start:
+				if result[-1].is_partial or gap > ALLOWABLE_GAP:
 					# there's a gap between prev end and this start, so add a None
 					if not allow_holes:
 						raise ContainsHoles

segment_coverage/segment_coverage/main.py

@@ -254,6 +254,9 @@ class CoverageChecker(object):
 		"""Loop over available hours for each quality, checking segment coverage."""
 		self.logger.info('Starting')
 
+		ALLOWABLE_OVERLAP = 0.01 # 10ms
+		ALLOWABLE_GAP = 0.01 # 10ms
+
 		while not self.stopping.is_set():
 
 			for quality in self.qualities:
@@ -374,7 +377,8 @@ class CoverageChecker(object):
 							previous_editable = best_segment
 						else:
 							previous_end = previous.start + previous.duration
-							if segment.start < previous_end:
+							gap = (segment.start - previous_end).total_seconds()
+							if gap < -ALLOWABLE_OVERLAP:
 								if segment.type == 'full':
 									full_overlaps += 1
 									full_overlap_duration += previous_end - segment.start
@@ -389,11 +393,11 @@ class CoverageChecker(object):
 								coverage += segment.duration
 								editable_coverage += segment.duration
 
-								if segment.start > previous_end:
+								if gap > ALLOWABLE_GAP:
 									holes.append((previous_end, segment.start))
 
 								previous_editable_end = previous_editable.start + previous_editable.duration
-								if segment.start > previous_editable_end:
+								if (segment.start - previous_editable_end).total_seconds() > ALLOWABLE_GAP:
 									editable_holes.append((previous_editable_end, segment.start))
 
 								previous_editable = best_segment