SCC: allow starting parsing from the middle of a caption

Skip until a caption style is specified

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

@@ -187,6 +187,10 @@ def get_lines(self) -> Dict[int, SccCaptionLine]:
     """Returns the paragraph lines per row"""
     return self._caption_lines
 
+  def is_empty(self) -> bool:
+    """Returns whether the paragraph has no content"""
+    return not self._caption_lines
+
   def copy_lines(self) -> Dict[int, SccCaptionLine]:
     """Copy paragraph lines (without time attributes)"""
     lines_copy = {}
@@ -265,6 +269,9 @@ def guess_text_alignment(self) -> TextAlignType:
     def get_line_right_offset(line: SccCaptionLine) -> int:
       return SCC_ROOT_CELL_RESOLUTION_COLUMNS - (line.get_indent() + line.get_length())
 
+    if self.is_empty():
+      return TextAlignType.start
+
     # look for longest line
     longest_line = max(self._caption_lines.values(), key=lambda line: line.get_length())
 

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

@@ -28,6 +28,7 @@
 from __future__ import annotations
 
 import copy
+import logging
 from typing import Optional, Type, Tuple
 
 from ttconv.model import Div
@@ -44,6 +45,8 @@
 
 ROLL_UP_BASE_ROW = 15
 
+LOGGER = logging.getLogger(__name__)
+
 
 class SccContext:
   """SCC context for reader"""
@@ -96,15 +99,17 @@ def new_buffered_caption(self):
     """Resets buffered caption"""
     self.buffered_caption = SccCaptionParagraph(self.safe_area_x_offset, self.safe_area_y_offset)
 
-  def get_caption_to_process(self):
+  def get_caption_to_process(self) -> Optional[SccCaptionParagraph]:
     """Returns the caption currently being processed"""
     if self.current_style in (SccCaptionStyle.PaintOn, SccCaptionStyle.RollUp):
       # If the Paint-On or Roll-Up style is activated, write directly on active caption
       return self.active_caption
     if self.current_style is SccCaptionStyle.PopOn:
       # For Pop-On style, write first on a buffered caption
       return self.buffered_caption
-    raise ValueError("SCC caption style not defined")
+
+    LOGGER.warning("SCC caption style not defined")
+    return None
 
   def has_active_caption(self) -> bool:
     """Returns whether captions are being displayed or not"""
@@ -147,7 +152,8 @@ def push_active_caption_to_model(self, time_code: SmpteTimeCode, clear_active_ca
       if clear_active_caption:
         self.active_caption = None
 
-      self.div.push_child(previous_caption.to_paragraph(self.div.get_doc()))
+      if not previous_caption.is_empty():
+        self.div.push_child(previous_caption.to_paragraph(self.div.get_doc()))
 
   def backspace(self):
     """Move the cursors in a column to the left"""
@@ -226,7 +232,7 @@ def process_preamble_address_code(self, pac: SccPreambleAddressCode, time_code:
       self.buffered_caption.set_cursor_at(pac_row, pac_indent)
 
     else:
-      raise ValueError("SCC caption style not defined")
+      LOGGER.warning("SCC caption style not defined")
 
     self.current_color = pac.get_color()
     self.current_font_style = pac.get_font_style()
@@ -248,8 +254,9 @@ def process_mid_row_code(self, mid_row_code: SccMidRowCode, time_code: SmpteTime
       # In case of multiple mid-row codes, move right only after the first code
 
       # If there is already text on the current line
-      if processed_caption.get_current_text() is not None \
-          and processed_caption.get_current_text().get_text() != "":
+      if processed_caption is not None \
+          and processed_caption.get_current_text() is not None \
+          and not processed_caption.get_current_text().is_empty():
 
         # In case of paint-on replacing text
         if self.current_style is SccCaptionStyle.PaintOn \
@@ -264,7 +271,7 @@ def process_mid_row_code(self, mid_row_code: SccMidRowCode, time_code: SmpteTime
             processed_caption.append_text(" ")
             processed_caption.new_caption_text()
 
-      else:
+      elif processed_caption is not None:
         processed_caption.append_text(" ")
 
       self.current_color = color
@@ -279,10 +286,12 @@ def process_mid_row_code(self, mid_row_code: SccMidRowCode, time_code: SmpteTime
       if text_decoration is not None:
         self.current_text_decoration = text_decoration
 
-      processed_caption.append_text(" ")
-      processed_caption.new_caption_text()
+      if processed_caption is not None:
+        processed_caption.append_text(" ")
+        processed_caption.new_caption_text()
 
-    if processed_caption.get_caption_style() is SccCaptionStyle.PaintOn:
+    if processed_caption is not None \
+        and processed_caption.get_caption_style() is SccCaptionStyle.PaintOn:
       processed_caption.get_current_text().set_begin(time_code)
 
   def process_attribute_code(self, attribute_code: SccAttributeCode):
@@ -291,7 +300,8 @@ def process_attribute_code(self, attribute_code: SccAttributeCode):
     processed_caption = self.get_caption_to_process()
 
     if processed_caption is None or processed_caption.get_current_text() is None:
-      raise ValueError("No current SCC caption nor content initialized")
+      LOGGER.warning("No current SCC caption nor content initialized")
+      return
 
     if processed_caption.get_current_text() is not None and processed_caption.get_current_text().get_text():
       processed_caption.new_caption_text()
@@ -460,7 +470,7 @@ def process_text(self, word: str, time_code: SmpteTimeCode):
       self.active_caption.get_current_text().add_style_property(StyleProperties.FontStyle, self.current_font_style)
       self.active_caption.get_current_text().add_style_property(StyleProperties.TextDecoration, self.current_text_decoration)
 
-    else:
+    elif self.current_style is SccCaptionStyle.PopOn:
       self.buffered_caption.append_text(word)
 
       self.buffered_caption.get_current_text().add_style_property(StyleProperties.Color, self.current_color)

src/test/python/test_scc_reader.py

@@ -1016,6 +1016,181 @@ def test_scc_mid_row_erase_displayed_memory_control_code(self):
     self.check_caption(p_list[5], "caption6", "00:00:03:19", None, "sagittis.")
     self.assertEqual(region_4, p_list[5].get_region())
 
+  def test_scc_content_parsing_from_text(self):
+    scc_content = """\
+Scenarist_SCC V1.0
+
+00:00:03:01	6970 7375 6d00 942c 942f
+
+00:00:07:29	9420 94D0 646f 6c6f 7220 7369 7420 616d 6574 2c80 9470 636f 6e73 6563 7465 7475 7220 6164 6970 6973 6369 6e67 2065 6c69 742e 942c 942f
+
+00:00:09:07	942c
+"""
+
+    scc_disassembly = """\
+00:00:03:01	ipsum{EDM}{EOC}
+00:00:07:29	{RCL}{1400}dolor sit amet,{1500}consectetur adipiscing elit.{EDM}{EOC}
+00:00:09:07	{EDM}
+"""
+
+    self.assertEqual(scc_disassembly, to_disassembly(scc_content))
+
+    doc = to_model(scc_content)
+    self.assertIsNotNone(doc)
+
+    region_1 = doc.get_region("pop1")
+    self.assertIsNotNone(region_1)
+    self.check_region_origin(region_1, 4, 15, doc.get_cell_resolution())
+    self.check_region_extent(region_1, 28, 2, doc.get_cell_resolution())
+    self.check_element_style(region_1, StyleProperties.DisplayAlign, DisplayAlignType.before)
+    self.check_element_style(region_1, StyleProperties.ShowBackground, ShowBackgroundType.whenActive)
+
+    body = doc.get_body()
+    self.assertIsNotNone(body)
+
+    div_list = list(body)
+    self.assertEqual(1, len(div_list))
+    div = div_list[0]
+    self.assertIsNotNone(div)
+
+    p_list = list(div)
+    self.assertEqual(1, len(p_list))
+
+    self.check_caption(p_list[0], "caption2", "00:00:08:26", "00:00:09:09", "dolor sit amet,", Br,
+                       "consectetur adipiscing elit.")
+    self.assertEqual(region_1, p_list[0].get_region())
+
+  def test_scc_content_parsing_from_mid_row_code(self):
+    scc_content = """\
+Scenarist_SCC V1.0
+
+00:00:03:01	91ae 6970 7375 6d00 942c 942f
+
+00:00:07:29	9420 94D0 646f 6c6f 7220 7369 7420 616d 6574 2c80 9470 636f 6e73 6563 7465 7475 7220 6164 6970 6973 6369 6e67 2065 6c69 742e 942c 942f
+
+00:00:09:07	942c
+"""
+
+    scc_disassembly = """\
+00:00:03:01	{I}ipsum{EDM}{EOC}
+00:00:07:29	{RCL}{1400}dolor sit amet,{1500}consectetur adipiscing elit.{EDM}{EOC}
+00:00:09:07	{EDM}
+"""
+
+    self.assertEqual(scc_disassembly, to_disassembly(scc_content))
+
+    doc = to_model(scc_content)
+    self.assertIsNotNone(doc)
+
+    region_1 = doc.get_region("pop1")
+    self.assertIsNotNone(region_1)
+    self.check_region_origin(region_1, 4, 15, doc.get_cell_resolution())
+    self.check_region_extent(region_1, 28, 2, doc.get_cell_resolution())
+    self.check_element_style(region_1, StyleProperties.DisplayAlign, DisplayAlignType.before)
+    self.check_element_style(region_1, StyleProperties.ShowBackground, ShowBackgroundType.whenActive)
+
+    body = doc.get_body()
+    self.assertIsNotNone(body)
+
+    div_list = list(body)
+    self.assertEqual(1, len(div_list))
+    div = div_list[0]
+    self.assertIsNotNone(div)
+
+    p_list = list(div)
+    self.assertEqual(1, len(p_list))
+
+    self.check_caption(p_list[0], "caption2", "00:00:08:26", "00:00:09:09", "dolor sit amet,", Br,
+                       "consectetur adipiscing elit.")
+    self.assertEqual(region_1, p_list[0].get_region())
+
+  def test_scc_content_parsing_from_control_code(self):
+    scc_content = """\
+Scenarist_SCC V1.0
+
+00:00:03:01	942c 6970 7375 6d00 942c 942f
+
+00:00:07:29	9420 94D0 646f 6c6f 7220 7369 7420 616d 6574 2c80 9470 636f 6e73 6563 7465 7475 7220 6164 6970 6973 6369 6e67 2065 6c69 742e 942c 942f
+
+00:00:09:07	942c
+"""
+
+    scc_disassembly = """\
+00:00:03:01	{EDM}ipsum{EDM}{EOC}
+00:00:07:29	{RCL}{1400}dolor sit amet,{1500}consectetur adipiscing elit.{EDM}{EOC}
+00:00:09:07	{EDM}
+"""
+
+    self.assertEqual(scc_disassembly, to_disassembly(scc_content))
+
+    doc = to_model(scc_content)
+    self.assertIsNotNone(doc)
+
+    region_1 = doc.get_region("pop1")
+    self.assertIsNotNone(region_1)
+    self.check_region_origin(region_1, 4, 15, doc.get_cell_resolution())
+    self.check_region_extent(region_1, 28, 2, doc.get_cell_resolution())
+    self.check_element_style(region_1, StyleProperties.DisplayAlign, DisplayAlignType.before)
+    self.check_element_style(region_1, StyleProperties.ShowBackground, ShowBackgroundType.whenActive)
+
+    body = doc.get_body()
+    self.assertIsNotNone(body)
+
+    div_list = list(body)
+    self.assertEqual(1, len(div_list))
+    div = div_list[0]
+    self.assertIsNotNone(div)
+
+    p_list = list(div)
+    self.assertEqual(1, len(p_list))
+
+    self.check_caption(p_list[0], "caption2", "00:00:08:26", "00:00:09:09", "dolor sit amet,", Br,
+                       "consectetur adipiscing elit.")
+    self.assertEqual(region_1, p_list[0].get_region())
+
+  def test_scc_content_parsing_from_preamble_address_code(self):
+    scc_content = """\
+Scenarist_SCC V1.0
+
+00:00:03:01	9370 6970 7375 6d00 942c 942f
+
+00:00:07:29	9420 94D0 646f 6c6f 7220 7369 7420 616d 6574 2c80 9470 636f 6e73 6563 7465 7475 7220 6164 6970 6973 6369 6e67 2065 6c69 742e 942c 942f
+
+00:00:09:07	942c
+"""
+
+    scc_disassembly = """\
+00:00:03:01	{1300}ipsum{EDM}{EOC}
+00:00:07:29	{RCL}{1400}dolor sit amet,{1500}consectetur adipiscing elit.{EDM}{EOC}
+00:00:09:07	{EDM}
+"""
+
+    self.assertEqual(scc_disassembly, to_disassembly(scc_content))
+
+    doc = to_model(scc_content)
+    self.assertIsNotNone(doc)
+
+    region_1 = doc.get_region("pop1")
+    self.assertIsNotNone(region_1)
+    self.check_region_origin(region_1, 4, 15, doc.get_cell_resolution())
+    self.check_region_extent(region_1, 28, 2, doc.get_cell_resolution())
+    self.check_element_style(region_1, StyleProperties.DisplayAlign, DisplayAlignType.before)
+    self.check_element_style(region_1, StyleProperties.ShowBackground, ShowBackgroundType.whenActive)
+
+    body = doc.get_body()
+    self.assertIsNotNone(body)
+
+    div_list = list(body)
+    self.assertEqual(1, len(div_list))
+    div = div_list[0]
+    self.assertIsNotNone(div)
+
+    p_list = list(div)
+    self.assertEqual(1, len(p_list))
+
+    self.check_caption(p_list[0], "caption2", "00:00:08:26", "00:00:09:09", "dolor sit amet,", Br,
+                       "consectetur adipiscing elit.")
+    self.assertEqual(region_1, p_list[0].get_region())
 
 if __name__ == '__main__':
   unittest.main()