src/pngenc/imp.rs

// Copyright (C) 2020 Natanael Mojica <neithanmo@gmail.com>
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use std::{io, io::Write, sync::Arc};

use gst::glib;
use gst::prelude::*;
use gst::subclass::prelude::*;
use gst::{gst_debug, gst_error};
use gst_video::prelude::*;
use gst_video::subclass::prelude::*;

use atomic_refcell::AtomicRefCell;
use once_cell::sync::Lazy;
use parking_lot::Mutex;

use super::CompressionLevel;
use super::FilterType;

const DEFAULT_COMPRESSION_LEVEL: CompressionLevel = CompressionLevel::Default;
const DEFAULT_FILTER_TYPE: FilterType = FilterType::NoFilter;

static CAT: Lazy<gst::DebugCategory> = Lazy::new(|| {
    gst::DebugCategory::new(
        "rspngenc",
        gst::DebugColorFlags::empty(),
        Some("PNG encoder"),
    )
});

// Inner buffer where the result of frame encoding  is written
// before relay them downstream
struct CacheBuffer {
    buffer: AtomicRefCell<Vec<u8>>,
}

impl CacheBuffer {
    pub fn new() -> Self {
        Self {
            buffer: AtomicRefCell::new(Vec::new()),
        }
    }

    pub fn clear(&self) {
        self.buffer.borrow_mut().clear();
    }

    pub fn write(&self, buf: &[u8]) {
        let mut buffer = self.buffer.borrow_mut();
        buffer.extend_from_slice(buf);
    }

    pub fn consume(&self) -> Vec<u8> {
        let mut buffer = self.buffer.borrow_mut();
        std::mem::take(&mut *buffer)
    }
}
// The Encoder requires a Writer, so we use here and intermediate structure
// for caching encoded frames
struct CacheWriter {
    cache: Arc<CacheBuffer>,
}

impl CacheWriter {
    pub fn new(cache: Arc<CacheBuffer>) -> Self {
        Self { cache }
    }
}

impl Write for CacheWriter {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.cache.write(buf);
        Ok(buf.len())
    }

    fn flush(&mut self) -> io::Result<()> {
        Ok(())
    }
}

#[derive(Debug, Clone, Copy)]
struct Settings {
    compression: CompressionLevel,
    filter: FilterType,
}

impl Default for Settings {
    fn default() -> Self {
        Settings {
            compression: DEFAULT_COMPRESSION_LEVEL,
            filter: DEFAULT_FILTER_TYPE,
        }
    }
}

struct State {
    video_info: gst_video::VideoInfo,
    cache: Arc<CacheBuffer>,
    writer: Option<png::Writer<CacheWriter>>,
}

impl State {
    fn new(video_info: gst_video::VideoInfo) -> Self {
        let cache = Arc::new(CacheBuffer::new());
        Self {
            video_info,
            cache,
            writer: None,
        }
    }

    fn reset(&mut self, settings: Settings) -> Result<(), gst::LoggableError> {
        // clear the cache
        self.cache.clear();
        let width = self.video_info.width();
        let height = self.video_info.height();
        let mut encoder = png::Encoder::new(CacheWriter::new(self.cache.clone()), width, height);
        let color = match self.video_info.format() {
            gst_video::VideoFormat::Gray8 | gst_video::VideoFormat::Gray16Be => {
                png::ColorType::Grayscale
            }
            gst_video::VideoFormat::Rgb => png::ColorType::Rgb,
            gst_video::VideoFormat::Rgba => png::ColorType::Rgba,
            _ => {
                gst_error!(CAT, "format is not supported yet");
                unreachable!()
            }
        };
        let depth = if self.video_info.format() == gst_video::VideoFormat::Gray16Be {
            png::BitDepth::Sixteen
        } else {
            png::BitDepth::Eight
        };

        encoder.set_color(color);
        encoder.set_depth(depth);
        encoder.set_compression(png::Compression::from(settings.compression));
        encoder.set_filter(png::FilterType::from(settings.filter));
        // Write the header for this video format into our inner buffer
        let writer = encoder.write_header().map_err(|e| {
            gst::loggable_error!(CAT, "Failed to create encoder error: {}", e.to_string())
        })?;
        self.writer = Some(writer);
        Ok(())
    }

    fn write_data(&mut self, data: &[u8]) -> Result<(), png::EncodingError> {
        if let Some(writer) = self.writer.as_mut() {
            writer.write_image_data(data)
        } else {
            unreachable!()
        }
    }
}

#[derive(Default)]
pub struct PngEncoder {
    state: Mutex<Option<State>>,
    settings: Mutex<Settings>,
}

#[glib::object_subclass]
impl ObjectSubclass for PngEncoder {
    const NAME: &'static str = "PngEncoder";
    type Type = super::PngEncoder;
    type ParentType = gst_video::VideoEncoder;
}

impl ObjectImpl for PngEncoder {
    fn properties() -> &'static [glib::ParamSpec] {
        static PROPERTIES: Lazy<Vec<glib::ParamSpec>> = Lazy::new(|| {
            vec![
                glib::ParamSpec::new_enum(
                    "compression-level",
                    "Compression level",
                    "Selects the compression algorithm to use",
                    CompressionLevel::static_type(),
                    DEFAULT_COMPRESSION_LEVEL as i32,
                    glib::ParamFlags::READWRITE | gst::PARAM_FLAG_MUTABLE_READY,
                ),
                glib::ParamSpec::new_enum(
                    "filter",
                    "Filter",
                    "Selects the filter type to applied",
                    FilterType::static_type(),
                    DEFAULT_FILTER_TYPE as i32,
                    glib::ParamFlags::READWRITE | gst::PARAM_FLAG_MUTABLE_READY,
                ),
            ]
        });

        PROPERTIES.as_ref()
    }

    fn set_property(
        &self,
        _obj: &Self::Type,
        _id: usize,
        value: &glib::Value,
        pspec: &glib::ParamSpec,
    ) {
        match pspec.name() {
            "compression-level" => {
                let mut settings = self.settings.lock();
                settings.compression = value
                    .get::<CompressionLevel>()
                    .expect("type checked upstream");
            }
            "filter" => {
                let mut settings = self.settings.lock();
                settings.filter = value.get::<FilterType>().expect("type checked upstream");
            }
            _ => unreachable!(),
        }
    }

    fn property(&self, _obj: &Self::Type, _id: usize, pspec: &glib::ParamSpec) -> glib::Value {
        match pspec.name() {
            "compression-level" => {
                let settings = self.settings.lock();
                settings.compression.to_value()
            }
            "filter" => {
                let settings = self.settings.lock();
                settings.filter.to_value()
            }
            _ => unimplemented!(),
        }
    }
}

impl ElementImpl for PngEncoder {
    fn metadata() -> Option<&'static gst::subclass::ElementMetadata> {
        static ELEMENT_METADATA: Lazy<gst::subclass::ElementMetadata> = Lazy::new(|| {
            gst::subclass::ElementMetadata::new(
                "PNG encoder",
                "Encoder/Video",
                "PNG encoder",
                "Natanael Mojica <neithanmo@gmail>",
            )
        });

        Some(&*ELEMENT_METADATA)
    }

    fn pad_templates() -> &'static [gst::PadTemplate] {
        static PAD_TEMPLATES: Lazy<Vec<gst::PadTemplate>> = Lazy::new(|| {
            let sink_caps = gst::Caps::new_simple(
                "video/x-raw",
                &[
                    (
                        "format",
                        &gst::List::new(&[
                            &gst_video::VideoFormat::Gray8.to_str(),
                            &gst_video::VideoFormat::Gray16Be.to_str(),
                            &gst_video::VideoFormat::Rgb.to_str(),
                            &gst_video::VideoFormat::Rgba.to_str(),
                        ]),
                    ),
                    ("width", &gst::IntRange::<i32>::new(1, std::i32::MAX)),
                    ("height", &gst::IntRange::<i32>::new(1, std::i32::MAX)),
                    (
                        "framerate",
                        &gst::FractionRange::new(
                            gst::Fraction::new(1, 1),
                            gst::Fraction::new(std::i32::MAX, 1),
                        ),
                    ),
                ],
            );
            let sink_pad_template = gst::PadTemplate::new(
                "sink",
                gst::PadDirection::Sink,
                gst::PadPresence::Always,
                &sink_caps,
            )
            .unwrap();

            let src_caps = gst::Caps::new_simple("image/png", &[]);
            let src_pad_template = gst::PadTemplate::new(
                "src",
                gst::PadDirection::Src,
                gst::PadPresence::Always,
                &src_caps,
            )
            .unwrap();

            vec![sink_pad_template, src_pad_template]
        });

        PAD_TEMPLATES.as_ref()
    }
}

impl VideoEncoderImpl for PngEncoder {
    fn stop(&self, _element: &Self::Type) -> Result<(), gst::ErrorMessage> {
        *self.state.lock() = None;
        Ok(())
    }

    fn set_format(
        &self,
        element: &Self::Type,
        state: &gst_video::VideoCodecState<'static, gst_video::video_codec_state::Readable>,
    ) -> Result<(), gst::LoggableError> {
        let video_info = state.info();
        gst_debug!(CAT, obj: element, "Setting format {:?}", video_info);
        {
            let settings = self.settings.lock();
            let mut state = State::new(video_info);
            state.reset(*settings)?;
            *self.state.lock() = Some(state);
        }

        let output_state = element
            .set_output_state(gst::Caps::new_simple("image/png", &[]), Some(state))
            .map_err(|_| gst::loggable_error!(CAT, "Failed to set output state"))?;
        element
            .negotiate(output_state)
            .map_err(|_| gst::loggable_error!(CAT, "Failed to negotiate"))
    }

    fn handle_frame(
        &self,
        element: &Self::Type,
        mut frame: gst_video::VideoCodecFrame,
    ) -> Result<gst::FlowSuccess, gst::FlowError> {
        let mut state_guard = self.state.lock();
        let state = state_guard.as_mut().ok_or(gst::FlowError::NotNegotiated)?;

        // FIXME: https://github.com/image-rs/image-png/issues/301
        {
            let settings = self.settings.lock();
            state.reset(*settings).map_err(|err| {
                err.log_with_object(element);
                gst::FlowError::Error
            })?;
        }

        gst_debug!(
            CAT,
            obj: element,
            "Sending frame {}",
            frame.system_frame_number()
        );
        {
            let input_buffer = frame.input_buffer().expect("frame without input buffer");

            let input_map = input_buffer.map_readable().unwrap();
            let data = input_map.as_slice();
            state.write_data(data).map_err(|e| {
                gst::element_error!(element, gst::CoreError::Failed, [&e.to_string()]);
                gst::FlowError::Error
            })?;
        }

        let buffer = state.cache.consume();
        drop(state_guard);

        let output_buffer = gst::Buffer::from_mut_slice(buffer);
        // There are no such incremental frames in the png format
        frame.set_flags(gst_video::VideoCodecFrameFlags::SYNC_POINT);
        frame.set_output_buffer(output_buffer);
        element.finish_frame(Some(frame))
    }
}