From 2a207cf3b8898b2c90ba1f044b4c75cdfe063542 Mon Sep 17 00:00:00 2001
From: Chad <Chad.Page@gmail.com>
Date: Sun, 17 Oct 2021 11:56:26 -0700
Subject: [PATCH 1/3] Fix off-by-one error in PAL RF TBC

---
 lddecode/core.py | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/lddecode/core.py b/lddecode/core.py
index 638df189b..d3271c708 100644
--- a/lddecode/core.py
+++ b/lddecode/core.py
@@ -1432,11 +1432,12 @@ def downscale_audio(
 # The Field class contains common features used by NTSC and PAL
 class Field:
     def __init__(
-        self, rf, decode, audio_offset=0, keepraw=True, prevfield=None, initphase=False
+        self, rf, decode, audio_offset=0, keepraw=True, prevfield=None, initphase=False, readloc = 0
     ):
         self.rawdata = decode["input"]
         self.data = decode
         self.initphase = initphase  # used for seeking or first field
+        self.readloc = readloc
 
         self.prevfield = prevfield
 
@@ -2496,13 +2497,17 @@ def rf_tbc(self, linelocs=None):
 
         # For output consistency reasons, linecount is set to 313 (i.e. 626 lines)
         # in PAL mode.  This needs to be corrected for RF TBC.
+        startline = self.lineoffset
         lc = self.linecount
-        if self.rf.system == "PAL" and not self.isFirstField:
-            lc = 312
+        endline = startline + lc
+
+        if self.rf.system == 'PAL' and lc == 312:
+            startline += 1
+            endline += 1
 
         output = []
 
-        for l in range(self.lineoffset, self.lineoffset + lc):
+        for l in range(startline, endline):
             scaled = scale(fdata, linelocs[l] - delay, linelocs[l + 1] - delay, linelen)
             output.append(np.round(scaled).astype(np.int16))
 
@@ -3455,6 +3460,7 @@ def decodefield(self, initphase=False):
             audio_offset=self.audio_offset,
             prevfield=self.curfield,
             initphase=initphase,
+            readloc = self.rawdecode['startloc']
         )
 
         try:

From 9d8761fd8da5797191858396995e9a9145e36c44 Mon Sep 17 00:00:00 2001
From: Chad <Chad.Page@gmail.com>
Date: Sun, 17 Oct 2021 11:58:55 -0700
Subject: [PATCH 2/3] comment fix

---
 lddecode/core.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/lddecode/core.py b/lddecode/core.py
index d3271c708..a10f8cd59 100644
--- a/lddecode/core.py
+++ b/lddecode/core.py
@@ -2495,13 +2495,12 @@ def rf_tbc(self, linelocs=None):
         # Adjust for the demodulation/filtering delays
         delay = self.rf.delays["video_white"]
 
-        # For output consistency reasons, linecount is set to 313 (i.e. 626 lines)
-        # in PAL mode.  This needs to be corrected for RF TBC.
         startline = self.lineoffset
         lc = self.linecount
         endline = startline + lc
 
         if self.rf.system == 'PAL' and lc == 312:
+            # Adjust the first and last lines for PAL so the RF TBC lines up
             startline += 1
             endline += 1
 

From 7d2c0a26ff96cc41f862ee59939dfee385b26134 Mon Sep 17 00:00:00 2001
From: Chad <Chad.Page@gmail.com>
Date: Sun, 17 Oct 2021 12:04:03 -0700
Subject: [PATCH 3/3] Fix it in a cleaner way, using EFM processing as example

---
 lddecode/core.py | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/lddecode/core.py b/lddecode/core.py
index a10f8cd59..afc65ea74 100644
--- a/lddecode/core.py
+++ b/lddecode/core.py
@@ -2495,14 +2495,9 @@ def rf_tbc(self, linelocs=None):
         # Adjust for the demodulation/filtering delays
         delay = self.rf.delays["video_white"]
 
-        startline = self.lineoffset
-        lc = self.linecount
-        endline = startline + lc
-
-        if self.rf.system == 'PAL' and lc == 312:
-            # Adjust the first and last lines for PAL so the RF TBC lines up
-            startline += 1
-            endline += 1
+        # On PAL, always ignore self.lineoffset
+        startline = self.lineoffset if self.rf.system == 'NTSC' else 1
+        endline = startline + self.linecount
 
         output = []