diff --git a/crates/av1/tools/extract_tables.py b/crates/av1/tools/extract_tables.py
index e64a931f1..a037a3765 100644
--- a/crates/av1/tools/extract_tables.py
+++ b/crates/av1/tools/extract_tables.py
@@ -49,7 +49,7 @@ def ev(expr):
 # --- constants: symbol table (section 3) ---
 pending = []
 for line in texts["03.symbols.md"].split("\n"):
-    m = re.match(r"^\|\s*`([A-Z][A-Z0-9_]*)`\s*\|\s*([^|]+?)\s*\|", line)
+    m = re.match(r"^\|\s*`([A-Z][A-Z0-9_]*)`\s*\|\s*([^\s|](?:[^|]*[^|\s])?)\s*\|", line)
     if m:
         pending.append((m.group(1), m.group(2)))
 # --- constants: value/name tables (section 6 semantics, section 8/9) ---
@@ -91,7 +91,7 @@ for name, val in pending:
 def cells(text):
     """Split one initialiser cell. A missing comma between two operands on separate lines
     (Split_Tx_Size in the spec text: `TX_32X32` / `TX_4X8`) yields two cells."""
-    parts = re.split(r"(?<=[A-Za-z0-9_])\s*\n\s*(?=[A-Za-z0-9_])", text.strip())
+    parts = re.split(r"(?<=[A-Za-z0-9_])[^\S\n]*\n[^\S\n]*(?=[A-Za-z0-9_])", text.strip())
     if len(parts) > 1:
         sys.stderr.write("note: missing comma in spec table between %s\n" % parts)
     return parts
@@ -132,10 +132,25 @@ def shape(x):
     return []
 
 
+# `~~~~` opens a block on its own line (with an optional `c` marker) and the next run of
+# tildes closes it. Walk the pairs with two linear searches instead of the lazy `(.*?)`
+# with re.S, which rescans the whole remaining text at every position (super-linear).
+FENCE_OPEN = re.compile(r"~~~~~?\s*c?\n")
+FENCE_CLOSE = re.compile(r"~~~~~?")
+
 tables = {}
 for f in files:
     t = texts[f]
-    for block in re.findall(r"~~~~~?\s*c?\n(.*?)~~~~~?", t, re.S):
+    pos = 0
+    while True:
+        m = FENCE_OPEN.search(t, pos)
+        if not m:
+            break
+        c = FENCE_CLOSE.search(t, m.end())
+        if not c:
+            break
+        block = t[m.end():c.start()]
+        pos = c.end()
         b = re.sub(r"//[^\n]*", "", block)
         b = re.sub(r"/\*.*?\*/", "", b, flags=re.S)
         for m in re.finditer(r"(?m)^\s*([A-Z][A-Za-z0-9_]*)\s*((?:\[[^\]=]*\]\s*)+)=\s*", b):
diff --git a/crates/hevc/tools/extract_tables.py b/crates/hevc/tools/extract_tables.py
index 6ee5759df..8b7d7d35e 100644
--- a/crates/hevc/tools/extract_tables.py
+++ b/crates/hevc/tools/extract_tables.py
@@ -44,7 +44,7 @@ def body_after(title_regex, stop_regex=r"^\s*(Table \d+-\d+ - |\d+\s+Rec\. ITU|R
 def init_values(table):
     vals = []
     for l in body_after(r"Table %s - Values of initValue" % re.escape(table)):
-        m = re.match(r"^\s*initValue\s+(.*)$", l)
+        m = re.match(r"^\s*initValue\s+(\S.*)$", l)
         if m:
             vals += [int(v) for v in m.group(1).split()]
     return vals
@@ -118,7 +118,7 @@ w("")
 # Table 7-6: default 8x8 scaling lists (intra matrixId 0..2, inter 3..5)
 intra, inter = [], []
 for l in body_after(r"Table 7-6 - Specification of default values of ScalingList"):
-    m = re.match(r"^\s*ScalingList\[ 1\.\.3 \]\[ (0\.\.2|3\.\.5) \]\[ i \]\s+(.*)$", l)
+    m = re.match(r"^\s*ScalingList\[ 1\.\.3 \]\[ (0\.\.2|3\.\.5) \]\[ i \]\s+(\S.*)$", l)
     if m:
         (intra if m.group(1) == "0..2" else inter).extend(int(v) for v in m.group(2).split())
 assert len(intra) == 64 and len(inter) == 64