closedcaption: Add Closed Caption to ST2038 element

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1777>

video/closedcaption/src/cctost2038anc/imp.rs

@@ -0,0 +1,351 @@
+// Copyright (C) 2024 Sebastian Dröge <sebastian@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 std::sync::Mutex;
+
+use gst::glib;
+use gst::prelude::*;
+use gst::subclass::prelude::*;
+
+use atomic_refcell::AtomicRefCell;
+
+use once_cell::sync::Lazy;
+
+use crate::st2038anc_utils::convert_to_st2038_buffer;
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+enum Format {
+    Cea608,
+    Cea708,
+}
+
+#[derive(Default)]
+struct State {
+    format: Option<Format>,
+}
+
+#[derive(Clone)]
+struct Settings {
+    c_not_y_channel: bool,
+    line_number: u16,
+    horizontal_offset: u16,
+}
+
+impl Default for Settings {
+    fn default() -> Self {
+        Settings {
+            c_not_y_channel: false,
+            line_number: 9,
+            horizontal_offset: 0,
+        }
+    }
+}
+
+pub struct CcToSt2038Anc {
+    sinkpad: gst::Pad,
+    srcpad: gst::Pad,
+
+    state: AtomicRefCell<State>,
+    settings: Mutex<Settings>,
+}
+
+static CAT: Lazy<gst::DebugCategory> = Lazy::new(|| {
+    gst::DebugCategory::new(
+        "cctost2038anc",
+        gst::DebugColorFlags::empty(),
+        Some("Closed Caption to ST-2038 ANC Element"),
+    )
+});
+
+impl CcToSt2038Anc {
+    fn sink_chain(
+        &self,
+        pad: &gst::Pad,
+        buffer: gst::Buffer,
+    ) -> Result<gst::FlowSuccess, gst::FlowError> {
+        gst::trace!(CAT, obj = pad, "Handling buffer {:?}", buffer);
+
+        let state = self.state.borrow_mut();
+        let settings = self.settings.lock().unwrap().clone();
+
+        let map = buffer.map_readable().map_err(|_| {
+            gst::error!(CAT, obj = pad, "Can't map buffer readable");
+
+            gst::FlowError::Error
+        })?;
+
+        let (did, sdid) = match state.format {
+            Some(Format::Cea608) => (0x61, 0x02),
+            Some(Format::Cea708) => (0x61, 0x01),
+            None => {
+                gst::error!(CAT, imp = self, "No caps set");
+                return Err(gst::FlowError::NotNegotiated);
+            }
+        };
+
+        let mut outbuf = match convert_to_st2038_buffer(
+            settings.c_not_y_channel,
+            settings.line_number,
+            settings.horizontal_offset,
+            did,
+            sdid,
+            &map,
+        ) {
+            Ok(outbuf) => outbuf,
+            Err(err) => {
+                gst::error!(
+                    CAT,
+                    imp = self,
+                    "Can't convert Closed Caption buffer: {err}"
+                );
+                return Err(gst::FlowError::Error);
+            }
+        };
+        drop(map);
+
+        {
+            let outbuf = outbuf.get_mut().unwrap();
+            let _ = buffer.copy_into(outbuf, gst::BUFFER_COPY_METADATA, ..);
+        }
+        drop(state);
+
+        self.srcpad.push(outbuf)
+    }
+
+    #[allow(clippy::single_match)]
+    fn sink_event(&self, pad: &gst::Pad, event: gst::Event) -> bool {
+        use gst::EventView;
+
+        gst::log!(CAT, obj = pad, "Handling event {:?}", event);
+        match event.view() {
+            EventView::Caps(ev) => {
+                let caps = ev.caps();
+                let s = caps.structure(0).unwrap();
+
+                let format = match s.name().as_str() {
+                    "closedcaption/x-cea-608" => Format::Cea608,
+                    "closedcaption/x-cea-708" => Format::Cea708,
+                    _ => {
+                        gst::error!(CAT, imp = self, "Unsupported caps {caps:?}");
+                        return false;
+                    }
+                };
+
+                gst::debug!(CAT, imp = self, "Configuring format {format:?}");
+
+                let mut state = self.state.borrow_mut();
+                state.format = Some(format);
+                drop(state);
+
+                return self.srcpad.push_event(
+                    gst::event::Caps::builder(&self.srcpad.pad_template_caps())
+                        .seqnum(ev.seqnum())
+                        .build(),
+                );
+            }
+            _ => (),
+        }
+
+        gst::Pad::event_default(pad, Some(&*self.obj()), event)
+    }
+}
+
+#[glib::object_subclass]
+impl ObjectSubclass for CcToSt2038Anc {
+    const NAME: &'static str = "GstCcToSt2038Anc";
+    type Type = super::CcToSt2038Anc;
+    type ParentType = gst::Element;
+
+    fn with_class(klass: &Self::Class) -> Self {
+        let templ = klass.pad_template("sink").unwrap();
+        let sinkpad = gst::Pad::builder_from_template(&templ)
+            .chain_function(|pad, parent, buffer| {
+                CcToSt2038Anc::catch_panic_pad_function(
+                    parent,
+                    || Err(gst::FlowError::Error),
+                    |this| this.sink_chain(pad, buffer),
+                )
+            })
+            .event_function(|pad, parent, event| {
+                CcToSt2038Anc::catch_panic_pad_function(
+                    parent,
+                    || false,
+                    |this| this.sink_event(pad, event),
+                )
+            })
+            .flags(gst::PadFlags::FIXED_CAPS)
+            .build();
+
+        let templ = klass.pad_template("src").unwrap();
+        let srcpad = gst::Pad::builder_from_template(&templ)
+            .flags(gst::PadFlags::FIXED_CAPS)
+            .build();
+
+        Self {
+            sinkpad,
+            srcpad,
+            state: AtomicRefCell::new(State::default()),
+            settings: Mutex::new(Settings::default()),
+        }
+    }
+}
+
+impl ObjectImpl for CcToSt2038Anc {
+    fn properties() -> &'static [glib::ParamSpec] {
+        static PROPERTIES: Lazy<Vec<glib::ParamSpec>> = Lazy::new(|| {
+            vec![
+                glib::ParamSpecBoolean::builder("c-not-y-channel")
+                    .nick("Y Not C Channel")
+                    .blurb("Set the y_not_c_channel flag in the output")
+                    .default_value(Settings::default().c_not_y_channel)
+                    .mutable_playing()
+                    .build(),
+                glib::ParamSpecUInt::builder("line-number")
+                    .nick("Line Number")
+                    .blurb("Line Number of the output")
+                    .default_value(Settings::default().line_number as u32)
+                    .maximum(2047)
+                    .mutable_playing()
+                    .build(),
+                glib::ParamSpecUInt::builder("horizontal-offset")
+                    .nick("Horizontal Offset")
+                    .blurb("Horizontal offset of the output")
+                    .default_value(Settings::default().horizontal_offset as u32)
+                    .maximum(4095)
+                    .mutable_playing()
+                    .build(),
+            ]
+        });
+
+        PROPERTIES.as_ref()
+    }
+
+    fn set_property(&self, _id: usize, value: &glib::Value, pspec: &glib::ParamSpec) {
+        match pspec.name() {
+            "c-not-y-channel" => {
+                let mut settings = self.settings.lock().unwrap();
+
+                settings.c_not_y_channel = value.get().expect("type checked upstream");
+            }
+            "line-number" => {
+                let mut settings = self.settings.lock().unwrap();
+
+                settings.line_number = value.get::<u32>().expect("type checked upstream") as u16;
+            }
+            "horizontal-offset" => {
+                let mut settings = self.settings.lock().unwrap();
+
+                settings.horizontal_offset =
+                    value.get::<u32>().expect("type checked upstream") as u16;
+            }
+            _ => unimplemented!(),
+        }
+    }
+
+    fn property(&self, _id: usize, pspec: &glib::ParamSpec) -> glib::Value {
+        match pspec.name() {
+            "c-not-y-channel" => {
+                let settings = self.settings.lock().unwrap();
+                settings.c_not_y_channel.to_value()
+            }
+            "line-number" => {
+                let settings = self.settings.lock().unwrap();
+                (settings.line_number as u32).to_value()
+            }
+            "horizontal-offset" => {
+                let settings = self.settings.lock().unwrap();
+                (settings.horizontal_offset as u32).to_value()
+            }
+            _ => unimplemented!(),
+        }
+    }
+
+    fn constructed(&self) {
+        self.parent_constructed();
+
+        let obj = self.obj();
+        obj.add_pad(&self.sinkpad).unwrap();
+        obj.add_pad(&self.srcpad).unwrap();
+    }
+}
+
+impl GstObjectImpl for CcToSt2038Anc {}
+
+impl ElementImpl for CcToSt2038Anc {
+    fn metadata() -> Option<&'static gst::subclass::ElementMetadata> {
+        static ELEMENT_METADATA: Lazy<gst::subclass::ElementMetadata> = Lazy::new(|| {
+            gst::subclass::ElementMetadata::new(
+                "CC to ST-2038 ANC",
+                "Generic",
+                "Converts Closed Captions to ST-2038 ANC",
+                "Sebastian Dröge <sebastian@centricular.com>",
+            )
+        });
+
+        Some(&*ELEMENT_METADATA)
+    }
+
+    fn pad_templates() -> &'static [gst::PadTemplate] {
+        static PAD_TEMPLATES: Lazy<Vec<gst::PadTemplate>> = Lazy::new(|| {
+            let src_pad_template = gst::PadTemplate::new(
+                "src",
+                gst::PadDirection::Src,
+                gst::PadPresence::Sometimes,
+                &gst::Caps::builder("meta/x-st-2038").build(),
+            )
+            .unwrap();
+
+            let sink_pad_template = gst::PadTemplate::new(
+                "sink",
+                gst::PadDirection::Sink,
+                gst::PadPresence::Always,
+                &[
+                    gst::Structure::builder("closedcaption/x-cea-608")
+                        .field("format", "s334-1a")
+                        .build(),
+                    gst::Structure::builder("closedcaption/x-cea-708")
+                        .field("format", "cdp")
+                        .build(),
+                ]
+                .into_iter()
+                .collect::<gst::Caps>(),
+            )
+            .unwrap();
+
+            vec![src_pad_template, sink_pad_template]
+        });
+
+        PAD_TEMPLATES.as_ref()
+    }
+
+    #[allow(clippy::single_match)]
+    fn change_state(
+        &self,
+        transition: gst::StateChange,
+    ) -> Result<gst::StateChangeSuccess, gst::StateChangeError> {
+        gst::trace!(CAT, imp = self, "Changing state {:?}", transition);
+
+        match transition {
+            gst::StateChange::ReadyToPaused => {
+                *self.state.borrow_mut() = State::default();
+            }
+            _ => (),
+        }
+
+        let ret = self.parent_change_state(transition)?;
+
+        match transition {
+            gst::StateChange::PausedToReady => {
+                *self.state.borrow_mut() = State::default();
+            }
+            _ => (),
+        }
+
+        Ok(ret)
+    }
+}

video/closedcaption/src/cctost2038anc/mod.rs

@@ -0,0 +1,25 @@
+// Copyright (C) 2024 Sebastian Dröge <sebastian@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 gst::prelude::*;
+
+mod imp;
+
+glib::wrapper! {
+    pub struct CcToSt2038Anc(ObjectSubclass<imp::CcToSt2038Anc>) @extends gst::Element, gst::Object;
+}
+
+pub fn register(plugin: &gst::Plugin) -> Result<(), glib::BoolError> {
+    gst::Element::register(
+        Some(plugin),
+        "cctost2038anc",
+        gst::Rank::NONE,
+        CcToSt2038Anc::static_type(),
+    )
+}

video/closedcaption/src/lib.rs

@@ -18,6 +18,7 @@ use gst::glib;
 use gst::prelude::*;
 
 mod ccdetect;
+mod cctost2038anc;
 mod ccutils;
 mod cea608overlay;
 mod cea608tocea708;
@@ -69,6 +70,7 @@ fn plugin_init(plugin: &gst::Plugin) -> Result<(), glib::BoolError> {
     st2038ancdemux::register(plugin)?;
     st2038ancmux::register(plugin)?;
     st2038anctocc::register(plugin)?;
+    cctost2038anc::register(plugin)?;
     Ok(())
 }
 

video/closedcaption/src/st2038anc_utils.rs

@@ -68,3 +68,75 @@ impl AncDataHeader {
         })
     }
 }
+
+fn extend_with_even_odd_parity(v: u8, checksum: &mut u16) -> u16 {
+    let parity = v.count_ones() & 1;
+    let res = if parity == 0 {
+        0x1_00 | (v as u16)
+    } else {
+        0x2_00 | (v as u16)
+    };
+
+    *checksum = checksum.wrapping_add(res);
+
+    res
+}
+
+pub(crate) fn convert_to_st2038_buffer(
+    c_not_y_channel: bool,
+    line_number: u16,
+    horizontal_offset: u16,
+    did: u8,
+    sdid: u8,
+    payload: &[u8],
+) -> Result<gst::Buffer, anyhow::Error> {
+    if payload.len() > 255 {
+        anyhow::bail!(
+            "Payload needs to be less than 256 bytes, got {}",
+            payload.len()
+        );
+    }
+
+    use anyhow::Context;
+    use bitstream_io::{BigEndian, BitWrite, BitWriter};
+
+    let mut output = Vec::with_capacity((70 + payload.len() * 10) / 8 + 1);
+
+    let mut w = BitWriter::endian(&mut output, BigEndian);
+
+    w.write::<u8>(6, 0b00_0000).context("zero bits")?;
+    w.write_bit(c_not_y_channel).context("c_not_y_channel")?;
+    w.write::<u16>(11, line_number).context("line number")?;
+    w.write::<u16>(12, horizontal_offset)
+        .context("horizontal offset")?;
+
+    let mut checksum = 0u16;
+
+    w.write::<u16>(10, extend_with_even_odd_parity(did, &mut checksum))
+        .context("DID")?;
+    w.write::<u16>(10, extend_with_even_odd_parity(sdid, &mut checksum))
+        .context("SDID")?;
+    w.write::<u16>(
+        10,
+        extend_with_even_odd_parity(payload.len() as u8, &mut checksum),
+    )
+    .context("data count")?;
+
+    for &b in payload {
+        w.write::<u16>(10, extend_with_even_odd_parity(b, &mut checksum))
+            .context("payload")?;
+    }
+
+    checksum &= 0x1_ff;
+    checksum |= ((!(checksum >> 8)) & 0x0_01) << 9;
+
+    w.write::<u16>(10, checksum).context("checksum")?;
+
+    while !w.byte_aligned() {
+        w.write_bit(true).context("padding")?;
+    }
+
+    w.flush().context("flushing")?;
+
+    Ok(gst::Buffer::from_mut_slice(output))
+}