closedcaption: move 608 utility functions to a separate file

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1112>

7 files changed, 500 insertions, 355 deletions

diff --git a/video/closedcaption/src/cea608tojson/imp.rs b/video/closedcaption/src/cea608tojson/imp.rs
index cf90b6f08..c513dff3a 100644
--- a/video/closedcaption/src/cea608tojson/imp.rs
+++ b/video/closedcaption/src/cea608tojson/imp.rs
@@ -29,8 +29,8 @@ use gst::glib;
 use gst::prelude::*;
 use gst::subclass::prelude::*;
 
-use crate::ffi;
-use crate::ttutils::{Cea608Mode, Chunk, Line, Lines, TextStyle};
+use crate::cea608utils::*;
+use crate::ttutils::{Chunk, Line, Lines};
 
 use atomic_refcell::AtomicRefCell;
 
@@ -195,7 +195,6 @@ impl Default for Settings {
 
 struct State {
     mode: Option<Cea608Mode>,
-    last_cc_data: Option<u16>,
     rows: BTreeMap<u32, Row>,
     first_pts: Option<gst::ClockTime>,
     current_pts: Option<gst::ClockTime>,
@@ -205,13 +204,13 @@ struct State {
     cursor: Cursor,
     pending_lines: Option<TimestampedLines>,
     settings: Settings,
+    cea608_state: Cea608StateTracker,
 }
 
 impl Default for State {
     fn default() -> Self {
         State {
             mode: None,
-            last_cc_data: None,
             rows: BTreeMap::new(),
             first_pts: gst::ClockTime::NONE,
             current_pts: gst::ClockTime::NONE,
@@ -226,6 +225,7 @@ impl Default for State {
             },
             pending_lines: None,
             settings: Settings::default(),
+            cea608_state: Cea608StateTracker::default(),
         }
     }
 }
@@ -246,152 +246,6 @@ static CAT: Lazy<gst::DebugCategory> = Lazy::new(|| {
     )
 });
 
-fn is_basicna(cc_data: u16) -> bool {
-    0x0000 != (0x6000 & cc_data)
-}
-
-fn is_preamble(cc_data: u16) -> bool {
-    0x1040 == (0x7040 & cc_data)
-}
-
-fn is_midrowchange(cc_data: u16) -> bool {
-    0x1120 == (0x7770 & cc_data)
-}
-
-fn is_specialna(cc_data: u16) -> bool {
-    0x1130 == (0x7770 & cc_data)
-}
-
-fn is_xds(cc_data: u16) -> bool {
-    0x0000 == (0x7070 & cc_data) && 0x0000 != (0x0F0F & cc_data)
-}
-
-fn is_westeu(cc_data: u16) -> bool {
-    0x1220 == (0x7660 & cc_data)
-}
-
-fn is_control(cc_data: u16) -> bool {
-    0x1420 == (0x7670 & cc_data) || 0x1720 == (0x7770 & cc_data)
-}
-
-fn parse_control(cc_data: u16) -> (ffi::eia608_control_t, i32) {
-    unsafe {
-        let mut chan = 0;
-        let cmd = ffi::eia608_parse_control(cc_data, &mut chan);
-
-        (cmd, chan)
-    }
-}
-
-#[derive(Debug)]
-struct Preamble {
-    row: i32,
-    col: i32,
-    style: TextStyle,
-    chan: i32,
-    underline: i32,
-}
-
-fn parse_preamble(cc_data: u16) -> Preamble {
-    unsafe {
-        let mut row = 0;
-        let mut col = 0;
-        let mut style = 0;
-        let mut chan = 0;
-        let mut underline = 0;
-
-        ffi::eia608_parse_preamble(
-            cc_data,
-            &mut row,
-            &mut col,
-            &mut style,
-            &mut chan,
-            &mut underline,
-        );
-
-        Preamble {
-            row,
-            col,
-            style: style.into(),
-            chan,
-            underline,
-        }
-    }
-}
-
-struct MidrowChange {
-    chan: i32,
-    style: TextStyle,
-    underline: bool,
-}
-
-fn parse_midrowchange(cc_data: u16) -> MidrowChange {
-    unsafe {
-        let mut chan = 0;
-        let mut style = 0;
-        let mut underline = 0;
-
-        ffi::eia608_parse_midrowchange(cc_data, &mut chan, &mut style, &mut underline);
-
-        MidrowChange {
-            chan,
-            style: style.into(),
-            underline: underline > 0,
-        }
-    }
-}
-
-fn eia608_to_utf8(cc_data: u16) -> (Option<char>, Option<char>, i32) {
-    unsafe {
-        let mut chan = 0;
-        let mut char1 = [0u8; 5usize];
-        let mut char2 = [0u8; 5usize];
-
-        let n_chars = ffi::eia608_to_utf8(
-            cc_data,
-            &mut chan,
-            char1.as_mut_ptr() as *mut _,
-            char2.as_mut_ptr() as *mut _,
-        );
-
-        let char1 = if n_chars > 0 {
-            Some(
-                std::ffi::CStr::from_bytes_with_nul_unchecked(&char1)
-                    .to_string_lossy()
-                    .chars()
-                    .next()
-                    .unwrap(),
-            )
-        } else {
-            None
-        };
-
-        let char2 = if n_chars > 1 {
-            Some(
-                std::ffi::CStr::from_bytes_with_nul_unchecked(&char2)
-                    .to_string_lossy()
-                    .chars()
-                    .next()
-                    .unwrap(),
-            )
-        } else {
-            None
-        };
-
-        (char1, char2, chan)
-    }
-}
-
-fn eia608_to_text(cc_data: u16) -> String {
-    unsafe {
-        let bufsz = ffi::eia608_to_text(std::ptr::null_mut(), 0, cc_data);
-        let mut data = Vec::with_capacity((bufsz + 1) as usize);
-        ffi::eia608_to_text(data.as_ptr() as *mut _, (bufsz + 1) as usize, cc_data);
-        data.set_len(bufsz as usize);
-        String::from_utf8_unchecked(data)
-    }
-}
-
 fn dump(
     imp: &Cea608ToJson,
     cc_data: u16,
@@ -492,6 +346,7 @@ impl State {
             }
 
             self.rows.clear();
+            self.cea608_state.flush();
         } else {
             for row in self.rows.values() {
                 if !row.is_empty() {
@@ -544,9 +399,11 @@ impl State {
         }
     }
 
-    fn decode_preamble(&mut self, imp: &Cea608ToJson, cc_data: u16) -> Option<TimestampedLines> {
-        let preamble = parse_preamble(cc_data);
-
+    fn handle_preamble(
+        &mut self,
+        imp: &Cea608ToJson,
+        preamble: Preamble,
+    ) -> Option<TimestampedLines> {
         if preamble.chan != 0 {
             return None;
         }
@@ -630,140 +487,17 @@ impl State {
         }
     }
 
-    fn decode_control(&mut self, imp: &Cea608ToJson, cc_data: u16) -> Option<TimestampedLines> {
-        let (cmd, chan) = parse_control(cc_data);
-
-        gst::log!(CAT, imp: imp, "Command for CC {}", chan);
-
-        if chan != 0 {
-            return None;
-        }
-
-        match cmd {
-            ffi::eia608_control_t_eia608_control_resume_direct_captioning => {
-                return self.update_mode(imp, Cea608Mode::PaintOn);
-            }
-            ffi::eia608_control_t_eia608_control_erase_display_memory => {
-                return match self.mode {
-                    Some(Cea608Mode::PopOn) => {
-                        self.clear = Some(true);
-                        self.drain_pending(imp)
-                    }
-                    _ => {
-                        let ret = self.drain(imp, true);
-                        self.clear = Some(true);
-                        ret
-                    }
-                };
-            }
-            ffi::eia608_control_t_eia608_control_roll_up_2 => {
-                return self.update_mode(imp, Cea608Mode::RollUp2);
-            }
-            ffi::eia608_control_t_eia608_control_roll_up_3 => {
-                return self.update_mode(imp, Cea608Mode::RollUp3);
-            }
-            ffi::eia608_control_t_eia608_control_roll_up_4 => {
-                return self.update_mode(imp, Cea608Mode::RollUp4);
-            }
-            ffi::eia608_control_t_eia608_control_carriage_return => {
-                gst::log!(CAT, imp: imp, "carriage return");
-
-                if let Some(mode) = self.mode {
-                    // https://www.law.cornell.edu/cfr/text/47/79.101 (f)(2)(i) (f)(3)(i)
-                    if mode.is_rollup() {
-                        let ret = if self.settings.unbuffered {
-                            let offset = match mode {
-                                Cea608Mode::RollUp2 => 1,
-                                Cea608Mode::RollUp3 => 2,
-                                Cea608Mode::RollUp4 => 3,
-                                _ => unreachable!(),
-                            };
-
-                            let top_row = self.cursor.row.saturating_sub(offset);
-
-                            // https://www.law.cornell.edu/cfr/text/47/79.101 (f)(1)(iii)
-                            self.rows.remove(&top_row);
-
-                            for row in top_row + 1..self.cursor.row + 1 {
-                                if let Some(mut row) = self.rows.remove(&row) {
-                                    row.row -= 1;
-                                    self.rows.insert(row.row, row);
-                                }
-                            }
-
-                            self.rows.insert(self.cursor.row, Row::new(self.cursor.row));
-                            self.drain(imp, false)
-                        } else {
-                            let ret = self.drain(imp, true);
-                            self.carriage_return = Some(true);
-                            ret
-                        };
-
-                        return ret;
-                    }
-                }
-            }
-            ffi::eia608_control_t_eia608_control_backspace => {
-                if let Some(row) = self.rows.get_mut(&self.cursor.row) {
-                    row.pop(&mut self.cursor);
-                }
-            }
-            ffi::eia608_control_t_eia608_control_resume_caption_loading => {
-                return self.update_mode(imp, Cea608Mode::PopOn);
-            }
-            ffi::eia608_control_t_eia608_control_erase_non_displayed_memory => {
-                if self.mode == Some(Cea608Mode::PopOn) {
-                    self.rows.clear();
-                }
-            }
-            ffi::eia608_control_t_eia608_control_end_of_caption => {
-                // https://www.law.cornell.edu/cfr/text/47/79.101 (f)(2)
-                self.update_mode(imp, Cea608Mode::PopOn);
-                self.first_pts = self.current_pts;
-                let ret = if self.settings.unbuffered {
-                    self.drain(imp, true)
-                } else {
-                    let ret = self.drain_pending(imp);
-                    self.pending_lines = self.drain(imp, true);
-                    ret
-                };
-                return ret;
-            }
-            ffi::eia608_control_t_eia608_tab_offset_0
-            | ffi::eia608_control_t_eia608_tab_offset_1
-            | ffi::eia608_control_t_eia608_tab_offset_2
-            | ffi::eia608_control_t_eia608_tab_offset_3 => {
-                self.cursor.col += (cmd - ffi::eia608_control_t_eia608_tab_offset_0) as usize;
-                // C.13 Right Margin Limitation
-                self.cursor.col = std::cmp::min(self.cursor.col, 31);
-            }
-            // TODO
-            ffi::eia608_control_t_eia608_control_alarm_off
-            | ffi::eia608_control_t_eia608_control_delete_to_end_of_row => {}
-            ffi::eia608_control_t_eia608_control_alarm_on
-            | ffi::eia608_control_t_eia608_control_text_restart
-            | ffi::eia608_control_t_eia608_control_text_resume_text_display => {}
-            _ => {
-                gst::warning!(CAT, imp: imp, "Unknown command {}!", cmd);
-            }
-        }
-
-        None
-    }
-
-    fn decode_text(&mut self, imp: &Cea608ToJson, cc_data: u16) {
-        let (char1, char2, chan) = eia608_to_utf8(cc_data);
-
-        if chan != 0 {
+    fn handle_text(&mut self, imp: &Cea608ToJson, text: Cea608Text) {
+        if text.chan != 0 {
             return;
         }
 
         if let Some(row) = self.rows.get_mut(&self.cursor.row) {
-            if is_westeu(cc_data) {
+            if text.code_space == CodeSpace::WestEU {
                 row.pop(&mut self.cursor);
             }
 
-            if (char1.is_some() || char2.is_some()) && self.first_pts.is_none() {
+            if (text.char1.is_some() || text.char2.is_some()) && self.first_pts.is_none() {
                 if let Some(mode) = self.mode {
                     if mode.is_rollup() || mode == Cea608Mode::PaintOn {
                         self.first_pts = self.current_pts;
@@ -771,11 +505,11 @@ impl State {
                 }
             }
 
-            if let Some(c) = char1 {
+            if let Some(c) = text.char1 {
                 row.push(&mut self.cursor, c);
             }
 
-            if let Some(c) = char2 {
+            if let Some(c) = text.char2 {
                 row.push(&mut self.cursor, c);
             }
         } else {
@@ -783,10 +517,8 @@ impl State {
         }
     }
 
-    fn decode_midrowchange(&mut self, cc_data: u16) {
+    fn handle_midrowchange(&mut self, midrowchange: MidRowChange) {
         if let Some(row) = self.rows.get_mut(&self.cursor.row) {
-            let midrowchange = parse_midrowchange(cc_data);
-
             if midrowchange.chan == 0 {
                 row.push_midrow(&mut self.cursor, midrowchange.style, midrowchange.underline);
             }
@@ -800,36 +532,127 @@ impl State {
         duration: Option<gst::ClockTime>,
         cc_data: u16,
     ) -> Option<TimestampedLines> {
-        if (is_specialna(cc_data) || is_control(cc_data)) && Some(cc_data) == self.last_cc_data {
-            gst::log!(CAT, imp: imp, "Skipping duplicate");
-            return None;
-        }
+        self.cea608_state.push_cc_data(cc_data);
 
-        self.last_cc_data = Some(cc_data);
-        self.current_pts = pts;
-        self.current_duration = duration;
+        while let Some(cea608) = self.cea608_state.pop() {
+            if matches!(cea608, Cea608::Duplicate) {
+                gst::log!(CAT, imp: imp, "Skipping duplicate");
+                return None;
+            }
 
-        if is_xds(cc_data) {
-            gst::log!(CAT, imp: imp, "XDS, ignoring");
-        } else if is_control(cc_data) {
-            gst::log!(CAT, imp: imp, "control!");
-            return self.decode_control(imp, cc_data);
-        } else if is_basicna(cc_data) || is_specialna(cc_data) || is_westeu(cc_data) {
-            if let Some(mode) = self.mode {
-                self.mode?;
-                gst::log!(CAT, imp: imp, "text");
-                self.decode_text(imp, cc_data);
+            self.current_pts = pts;
+            self.current_duration = duration;
 
-                if mode.is_rollup() && self.settings.unbuffered {
-                    return self.drain(imp, false);
+            match cea608 {
+                Cea608::Duplicate => unreachable!(),
+                Cea608::EraseDisplay(chan) => {
+                    if chan == 0 {
+                        return match self.mode {
+                            Some(Cea608Mode::PopOn) => {
+                                self.clear = Some(true);
+                                self.drain_pending(imp)
+                            }
+                            _ => {
+                                let ret = self.drain(imp, true);
+                                self.clear = Some(true);
+                                ret
+                            }
+                        };
+                    }
+                }
+                Cea608::NewMode(chan, mode) => {
+                    if chan == 0 {
+                        return self.update_mode(imp, mode);
+                    }
+                }
+                Cea608::CarriageReturn(chan) => {
+                    if chan == 0 {
+                        gst::log!(CAT, imp: imp, "carriage return");
+
+                        if let Some(mode) = self.mode {
+                            // https://www.law.cornell.edu/cfr/text/47/79.101 (f)(2)(i) (f)(3)(i)
+                            if mode.is_rollup() {
+                                let ret = if self.settings.unbuffered {
+                                    let offset = match mode {
+                                        Cea608Mode::RollUp2 => 1,
+                                        Cea608Mode::RollUp3 => 2,
+                                        Cea608Mode::RollUp4 => 3,
+                                        _ => unreachable!(),
+                                    };
+
+                                    let top_row = self.cursor.row.saturating_sub(offset);
+
+                                    // https://www.law.cornell.edu/cfr/text/47/79.101 (f)(1)(iii)
+                                    self.rows.remove(&top_row);
+
+                                    for row in top_row + 1..self.cursor.row + 1 {
+                                        if let Some(mut row) = self.rows.remove(&row) {
+                                            row.row -= 1;
+                                            self.rows.insert(row.row, row);
+                                        }
+                                    }
+
+                                    self.rows.insert(self.cursor.row, Row::new(self.cursor.row));
+                                    self.drain(imp, false)
+                                } else {
+                                    let ret = self.drain(imp, true);
+                                    self.carriage_return = Some(true);
+                                    ret
+                                };
+
+                                return ret;
+                            }
+                        }
+                    }
+                }
+                Cea608::Backspace(chan) => {
+                    if chan == 0 {
+                        if let Some(row) = self.rows.get_mut(&self.cursor.row) {
+                            row.pop(&mut self.cursor);
+                        }
+                    }
+                }
+                Cea608::EraseNonDisplay(chan) => {
+                    if chan == 0 && self.mode == Some(Cea608Mode::PopOn) {
+                        self.rows.clear();
+                    }
+                }
+                Cea608::EndOfCaption(chan) => {
+                    if chan == 0 {
+                        // https://www.law.cornell.edu/cfr/text/47/79.101 (f)(2)
+                        self.update_mode(imp, Cea608Mode::PopOn);
+                        self.first_pts = self.current_pts;
+                        let ret = if self.settings.unbuffered {
+                            self.drain(imp, true)
+                        } else {
+                            let ret = self.drain_pending(imp);
+                            self.pending_lines = self.drain(imp, true);
+                            ret
+                        };
+                        return ret;
+                    }
+                }
+                Cea608::TabOffset(chan, count) => {
+                    if chan == 0 {
+                        self.cursor.col += count as usize;
+                        // C.13 Right Margin Limitation
+                        self.cursor.col = std::cmp::min(self.cursor.col, 31);
+                    }
+                }
+                Cea608::Text(text) => {
+                    if let Some(mode) = self.mode {
+                        self.mode?;
+                        gst::log!(CAT, imp: imp, "text");
+                        self.handle_text(imp, text);
+
+                        if mode.is_rollup() && self.settings.unbuffered {
+                            return self.drain(imp, false);
+                        }
+                    }
                 }
+                Cea608::Preamble(preamble) => return self.handle_preamble(imp, preamble),
+                Cea608::MidRowChange(change) => self.handle_midrowchange(change),
             }
-        } else if is_preamble(cc_data) {
-            gst::log!(CAT, imp: imp, "preamble");
-            return self.decode_preamble(imp, cc_data);
-        } else if is_midrowchange(cc_data) {
-            gst::log!(CAT, imp: imp, "midrowchange");
-            self.decode_midrowchange(cc_data);
         }
         None
     }
diff --git a/video/closedcaption/src/cea608utils.rs b/video/closedcaption/src/cea608utils.rs
new file mode 100644
index 000000000..c2415b905
--- /dev/null
+++ b/video/closedcaption/src/cea608utils.rs
@@ -0,0 +1,359 @@
+// Copyright (C) 2023 Matthew Waters <matthew@centricular.com>
+//
+// This Source Code Form is subject to the terms of the Mozilla Public License, v2.0.
+// If a copy of the MPL was not distributed with this file, You can obtain one at
+// <https://mozilla.org/MPL/2.0/>.
+//
+// SPDX-License-Identifier: MPL-2.0
+
+use gst::glib;
+use once_cell::sync::Lazy;
+use serde::{Deserialize, Serialize};
+
+use crate::ffi;
+
+static CAT: Lazy<gst::DebugCategory> = Lazy::new(|| {
+    gst::DebugCategory::new(
+        "cea608utils",
+        gst::DebugColorFlags::empty(),
+        Some("CEA-608 utilities"),
+    )
+});
+
+#[derive(
+    Serialize, Deserialize, Debug, Eq, PartialEq, Ord, PartialOrd, Hash, Clone, Copy, glib::Enum,
+)]
+#[repr(u32)]
+#[enum_type(name = "GstTtToCea608Mode")]
+pub enum Cea608Mode {
+    PopOn,
+    PaintOn,
+    RollUp2,
+    RollUp3,
+    RollUp4,
+}
+
+#[derive(Clone, Copy, Serialize, Deserialize, Debug, PartialEq, Eq)]
+pub enum TextStyle {
+    White,
+    Green,
+    Blue,
+    Cyan,
+    Red,
+    Yellow,
+    Magenta,
+    ItalicWhite,
+}
+
+impl From<u32> for TextStyle {
+    fn from(val: u32) -> Self {
+        match val {
+            0 => TextStyle::White,
+            1 => TextStyle::Green,
+            2 => TextStyle::Blue,
+            3 => TextStyle::Cyan,
+            4 => TextStyle::Red,
+            5 => TextStyle::Yellow,
+            6 => TextStyle::Magenta,
+            7 => TextStyle::ItalicWhite,
+            _ => TextStyle::White,
+        }
+    }
+}
+
+pub(crate) fn is_basicna(cc_data: u16) -> bool {
+    0x0000 != (0x6000 & cc_data)
+}
+
+pub(crate) fn is_preamble(cc_data: u16) -> bool {
+    0x1040 == (0x7040 & cc_data)
+}
+
+pub(crate) fn is_midrowchange(cc_data: u16) -> bool {
+    0x1120 == (0x7770 & cc_data)
+}
+
+pub(crate) fn is_specialna(cc_data: u16) -> bool {
+    0x1130 == (0x7770 & cc_data)
+}
+
+pub(crate) fn is_xds(cc_data: u16) -> bool {
+    0x0000 == (0x7070 & cc_data) && 0x0000 != (0x0F0F & cc_data)
+}
+
+pub(crate) fn is_westeu(cc_data: u16) -> bool {
+    0x1220 == (0x7660 & cc_data)
+}
+
+pub(crate) fn is_control(cc_data: u16) -> bool {
+    0x1420 == (0x7670 & cc_data) || 0x1720 == (0x7770 & cc_data)
+}
+
+pub(crate) fn parse_control(cc_data: u16) -> (ffi::eia608_control_t, i32) {
+    unsafe {
+        let mut chan = 0;
+        let cmd = ffi::eia608_parse_control(cc_data, &mut chan);
+
+        (cmd, chan)
+    }
+}
+
+#[derive(Debug)]
+pub(crate) struct Preamble {
+    pub row: i32,
+    pub col: i32,
+    pub style: TextStyle,
+    pub chan: i32,
+    pub underline: i32,
+}
+
+pub(crate) fn parse_preamble(cc_data: u16) -> Preamble {
+    unsafe {
+        let mut row = 0;
+        let mut col = 0;
+        let mut style = 0;
+        let mut chan = 0;
+        let mut underline = 0;
+
+        ffi::eia608_parse_preamble(
+            cc_data,
+            &mut row,
+            &mut col,
+            &mut style,
+            &mut chan,
+            &mut underline,
+        );
+
+        Preamble {
+            row,
+            col,
+            style: style.into(),
+            chan,
+            underline,
+        }
+    }
+}
+
+#[derive(Debug)]
+pub(crate) struct MidRowChange {
+    pub chan: i32,
+    pub style: TextStyle,
+    pub underline: bool,
+}
+
+pub(crate) fn parse_midrowchange(cc_data: u16) -> MidRowChange {
+    unsafe {
+        let mut chan = 0;
+        let mut style = 0;
+        let mut underline = 0;
+
+        ffi::eia608_parse_midrowchange(cc_data, &mut chan, &mut style, &mut underline);
+
+        MidRowChange {
+            chan,
+            style: style.into(),
+            underline: underline > 0,
+        }
+    }
+}
+
+pub(crate) fn eia608_to_utf8(cc_data: u16) -> (Option<char>, Option<char>, i32) {
+    unsafe {
+        let mut chan = 0;
+        let mut char1 = [0u8; 5usize];
+        let mut char2 = [0u8; 5usize];
+
+        let n_chars = ffi::eia608_to_utf8(
+            cc_data,
+            &mut chan,
+            char1.as_mut_ptr() as *mut _,
+            char2.as_mut_ptr() as *mut _,
+        );
+
+        let char1 = if n_chars > 0 {
+            Some(
+                std::ffi::CStr::from_bytes_with_nul_unchecked(&char1)
+                    .to_string_lossy()
+                    .chars()
+                    .next()
+                    .unwrap(),
+            )
+        } else {
+            None
+        };
+
+        let char2 = if n_chars > 1 {
+            Some(
+                std::ffi::CStr::from_bytes_with_nul_unchecked(&char2)
+                    .to_string_lossy()
+                    .chars()
+                    .next()
+                    .unwrap(),
+            )
+        } else {
+            None
+        };
+
+        (char1, char2, chan)
+    }
+}
+
+pub(crate) fn eia608_to_text(cc_data: u16) -> String {
+    unsafe {
+        let bufsz = ffi::eia608_to_text(std::ptr::null_mut(), 0, cc_data);
+        let mut data = Vec::with_capacity((bufsz + 1) as usize);
+        ffi::eia608_to_text(data.as_ptr() as *mut _, (bufsz + 1) as usize, cc_data);
+        data.set_len(bufsz as usize);
+        String::from_utf8_unchecked(data)
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub(crate) enum CodeSpace {
+    BasicNA,
+    SpecialNA,
+    WestEU,
+}
+
+impl CodeSpace {
+    fn from_cc_data(cc_data: u16) -> Self {
+        if is_basicna(cc_data) {
+            Self::BasicNA
+        } else if is_specialna(cc_data) {
+            Self::SpecialNA
+        } else if is_westeu(cc_data) {
+            Self::WestEU
+        } else {
+            unreachable!()
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub(crate) struct Cea608Text {
+    pub char1: Option<char>,
+    pub char2: Option<char>,
+    pub code_space: CodeSpace,
+    pub chan: i32,
+}
+
+#[derive(Debug)]
+pub(crate) enum Cea608 {
+    Duplicate,
+    NewMode(i32, Cea608Mode),
+    EraseDisplay(i32),
+    EraseNonDisplay(i32),
+    CarriageReturn(i32),
+    Backspace(i32),
+    EndOfCaption(i32),
+    TabOffset(i32, u32),
+    Text(Cea608Text),
+    Preamble(Preamble),
+    MidRowChange(MidRowChange),
+}
+
+fn decode_control(cc_data: u16) -> Option<Cea608> {
+    let (cmd, chan) = parse_control(cc_data);
+
+    gst::log!(CAT, "Command for CC {}", chan);
+
+    match cmd {
+        ffi::eia608_control_t_eia608_control_resume_direct_captioning => {
+            return Some(Cea608::NewMode(chan, Cea608Mode::PaintOn));
+        }
+        ffi::eia608_control_t_eia608_control_erase_display_memory => {
+            return Some(Cea608::EraseDisplay(chan));
+        }
+        ffi::eia608_control_t_eia608_control_roll_up_2 => {
+            return Some(Cea608::NewMode(chan, Cea608Mode::RollUp2));
+        }
+        ffi::eia608_control_t_eia608_control_roll_up_3 => {
+            return Some(Cea608::NewMode(chan, Cea608Mode::RollUp3));
+        }
+        ffi::eia608_control_t_eia608_control_roll_up_4 => {
+            return Some(Cea608::NewMode(chan, Cea608Mode::RollUp4));
+        }
+        ffi::eia608_control_t_eia608_control_carriage_return => {
+            return Some(Cea608::CarriageReturn(chan));
+        }
+        ffi::eia608_control_t_eia608_control_backspace => {
+            return Some(Cea608::Backspace(chan));
+        }
+        ffi::eia608_control_t_eia608_control_resume_caption_loading => {
+            return Some(Cea608::NewMode(chan, Cea608Mode::PopOn));
+        }
+        ffi::eia608_control_t_eia608_control_erase_non_displayed_memory => {
+            return Some(Cea608::EraseNonDisplay(chan));
+        }
+        ffi::eia608_control_t_eia608_control_end_of_caption => {
+            return Some(Cea608::EndOfCaption(chan));
+        }
+        ffi::eia608_control_t_eia608_tab_offset_0
+        | ffi::eia608_control_t_eia608_tab_offset_1
+        | ffi::eia608_control_t_eia608_tab_offset_2
+        | ffi::eia608_control_t_eia608_tab_offset_3 => {
+            return Some(Cea608::TabOffset(
+                chan,
+                cmd - ffi::eia608_control_t_eia608_tab_offset_0,
+            ));
+        }
+        // TODO
+        ffi::eia608_control_t_eia608_control_alarm_off
+        | ffi::eia608_control_t_eia608_control_delete_to_end_of_row => {}
+        ffi::eia608_control_t_eia608_control_alarm_on
+        | ffi::eia608_control_t_eia608_control_text_restart
+        | ffi::eia608_control_t_eia608_control_text_resume_text_display => {}
+        _ => {
+            return None;
+        }
+    }
+    None
+}
+
+#[derive(Debug, Default)]
+pub(crate) struct Cea608StateTracker {
+    last_cc_data: Option<u16>,
+    pending_output: Vec<Cea608>,
+}
+
+impl Cea608StateTracker {
+    pub(crate) fn push_cc_data(&mut self, cc_data: u16) {
+        if (is_specialna(cc_data) || is_control(cc_data)) && Some(cc_data) == self.last_cc_data {
+            gst::log!(CAT, "Skipping duplicate");
+            self.pending_output.push(Cea608::Duplicate);
+            return;
+        }
+
+        if is_xds(cc_data) {
+            gst::log!(CAT, "XDS, ignoring");
+        } else if is_control(cc_data) {
+            if let Some(d) = decode_control(cc_data) {
+                self.pending_output.push(d);
+            }
+        } else if is_basicna(cc_data) || is_specialna(cc_data) || is_westeu(cc_data) {
+            let (char1, char2, chan) = eia608_to_utf8(cc_data);
+            if char1.is_some() || char2.is_some() {
+                self.pending_output.push(Cea608::Text(Cea608Text {
+                    char1,
+                    char2,
+                    code_space: CodeSpace::from_cc_data(cc_data),
+                    chan,
+                }));
+            }
+        } else if is_preamble(cc_data) {
+            self.pending_output
+                .push(Cea608::Preamble(parse_preamble(cc_data)));
+        } else if is_midrowchange(cc_data) {
+            self.pending_output
+                .push(Cea608::MidRowChange(parse_midrowchange(cc_data)));
+        }
+    }
+
+    pub(crate) fn pop(&mut self) -> Option<Cea608> {
+        self.pending_output.pop()
+    }
+
+    pub(crate) fn flush(&mut self) {
+        self.pending_output = vec![];
+    }
+}
diff --git a/video/closedcaption/src/lib.rs b/video/closedcaption/src/lib.rs
index 107a940b8..ec99b26e8 100644
--- a/video/closedcaption/src/lib.rs
+++ b/video/closedcaption/src/lib.rs
@@ -28,6 +28,7 @@ mod ccutils;
 mod cea608overlay;
 mod cea608tojson;
 mod cea608tott;
+mod cea608utils;
 mod jsontovtt;
 mod line_reader;
 mod mcc_enc;
@@ -42,7 +43,7 @@ mod ttutils;
 
 fn plugin_init(plugin: &gst::Plugin) -> Result<(), glib::BoolError> {
     #[cfg(feature = "doc")]
-    ttutils::Cea608Mode::static_type().mark_as_plugin_api(gst::PluginAPIFlags::empty());
+    cea608utils::Cea608Mode::static_type().mark_as_plugin_api(gst::PluginAPIFlags::empty());
     mcc_parse::register(plugin)?;
     mcc_enc::register(plugin)?;
     scc_parse::register(plugin)?;
diff --git a/video/closedcaption/src/transcriberbin/imp.rs b/video/closedcaption/src/transcriberbin/imp.rs
index ae67a477d..1240c137d 100644
--- a/video/closedcaption/src/transcriberbin/imp.rs
+++ b/video/closedcaption/src/transcriberbin/imp.rs
@@ -6,7 +6,7 @@
 //
 // SPDX-License-Identifier: MPL-2.0
 
-use crate::ttutils::Cea608Mode;
+use crate::cea608utils::Cea608Mode;
 use anyhow::{anyhow, Error};
 use gst::glib;
 use gst::prelude::*;
diff --git a/video/closedcaption/src/tttocea608/imp.rs b/video/closedcaption/src/tttocea608/imp.rs
index ac186e27d..2d8b931c7 100644
--- a/video/closedcaption/src/tttocea608/imp.rs
+++ b/video/closedcaption/src/tttocea608/imp.rs
@@ -15,7 +15,8 @@ use once_cell::sync::Lazy;
 use crate::ffi;
 use std::sync::Mutex;
 
-use crate::ttutils::{Cea608Mode, Chunk, Line, Lines, TextStyle};
+use crate::cea608utils::{Cea608Mode, TextStyle};
+use crate::ttutils::{Chunk, Line, Lines};
 
 fn is_punctuation(word: &str) -> bool {
     word == "." || word == "," || word == "?" || word == "!" || word == ";" || word == ":"
diff --git a/video/closedcaption/src/tttojson/imp.rs b/video/closedcaption/src/tttojson/imp.rs
index 688213ea9..b8d4228e2 100644
--- a/video/closedcaption/src/tttojson/imp.rs
+++ b/video/closedcaption/src/tttojson/imp.rs
@@ -15,7 +15,8 @@ use once_cell::sync::Lazy;
 use std::cmp::min;
 use std::sync::Mutex;
 
-use crate::ttutils::{Cea608Mode, Chunk, Line, Lines, TextStyle};
+use crate::cea608utils::*;
+use crate::ttutils::{Chunk, Line, Lines};
 
 static CAT: Lazy<gst::DebugCategory> = Lazy::new(|| {
     gst::DebugCategory::new(
diff --git a/video/closedcaption/src/ttutils.rs b/video/closedcaption/src/ttutils.rs
index 2c6f3a55b..84bd661d1 100644
--- a/video/closedcaption/src/ttutils.rs
+++ b/video/closedcaption/src/ttutils.rs
@@ -6,49 +6,9 @@
 //
 // SPDX-License-Identifier: MPL-2.0
 
-use gst::glib;
 use serde::{Deserialize, Serialize};
 
-#[derive(
-    Serialize, Deserialize, Debug, Eq, PartialEq, Ord, PartialOrd, Hash, Clone, Copy, glib::Enum,
-)]
-#[repr(u32)]
-#[enum_type(name = "GstTtToCea608Mode")]
-pub enum Cea608Mode {
-    PopOn,
-    PaintOn,
-    RollUp2,
-    RollUp3,
-    RollUp4,
-}
-
-#[derive(Clone, Copy, Serialize, Deserialize, Debug, PartialEq, Eq)]
-pub enum TextStyle {
-    White,
-    Green,
-    Blue,
-    Cyan,
-    Red,
-    Yellow,
-    Magenta,
-    ItalicWhite,
-}
-
-impl From<u32> for TextStyle {
-    fn from(val: u32) -> Self {
-        match val {
-            0 => TextStyle::White,
-            1 => TextStyle::Green,
-            2 => TextStyle::Blue,
-            3 => TextStyle::Cyan,
-            4 => TextStyle::Red,
-            5 => TextStyle::Yellow,
-            6 => TextStyle::Magenta,
-            7 => TextStyle::ItalicWhite,
-            _ => TextStyle::White,
-        }
-    }
-}
+use crate::cea608utils::*;
 
 // TODO allow indenting chunks
 #[derive(Clone, Serialize, Deserialize, Debug)]