SCC reader: fix begin/end computation from SCC timestamp

#454

Author: palemieux

.github/workflows/main.yml

@@ -4,7 +4,7 @@ on: [push, pull_request]
 
 jobs:
   run:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     if: github.event_name == 'push' || (github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name != github.repository)
     steps:
 

src/main/python/ttconv/scc/context.py

@@ -368,14 +368,7 @@ def process_control_code(self, control_code: SccControlCode, time_code: SmpteTim
     elif control_code is SccControlCode.EDM:
       # Erase displayed captions
       if self.has_active_caption():
-        if time_code is not None:
-          # End time is exclusive in the model, set it to the next frame
-          end_time_code = copy.copy(time_code)
-          end_time_code.add_frames()
-        else:
-          end_time_code = time_code
-
-        self.push_active_caption_to_model(end_time_code)
+        self.push_active_caption_to_model(time_code)
 
     elif control_code is SccControlCode.ENM:
       # Erase buffered caption

src/main/python/ttconv/scc/line.py

@@ -109,14 +109,16 @@ def process(self, context: SccContext) -> SmpteTimeCode:
 
     debug = str(self.time_code) + "\t"
 
+    first = True
     for scc_word in self.scc_words:
+      if not first:
+        self.time_code.add_frames()
+      first = False
 
       if context.previous_word is not None and context.previous_word.value == scc_word.value and context.previous_word.is_code():
         context.previous_word = None
         continue
 
-      self.time_code.add_frames()
-
       if scc_word.value == 0x0000:
         continue