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//! Output frame reordering.
//!
//! NihAV decoders output frames in the same order as they are put in.
//! In result if you want to have frames in display order you might need some frame reorderer.
//! This module provides such functionality depending on codec type: audio codecs and video codecs without B-frames do not need any reorderer and can use `NoReorderer` if the common interface is required. Codecs with B-frames should use `IPBReorderer`. For codecs with very complex reordering rules like H.264 or H.256 `PictureIDReorderer` will be added eventually.
//!
//! You can find out required reorderer by quering codec properties using `nihav_core::register` module.
use std::mem::swap;
pub use crate::frame::{FrameType, NAFrameRef};
/// A trait for frame reorderer.
pub trait FrameReorderer {
/// Stores a newly decoded frame.
fn add_frame(&mut self, fref: NAFrameRef) -> bool;
/// Gets the next frame to be displayed (or `None` if that is not possible).
fn get_frame(&mut self) -> Option<NAFrameRef>;
/// Clears all stored frames.
fn flush(&mut self);
/// Retrieves the last frames stored by the reorderer.
fn get_last_frames(&mut self) -> Option<NAFrameRef>;
}
/// Zero reorderer.
pub struct NoReorderer {
fref: Option<NAFrameRef>,
}
impl NoReorderer {
/// Constructs a new instance of `NoReorderer`.
pub fn new() -> Self {
Self { fref: None }
}
}
impl Default for NoReorderer {
fn default() -> Self {
Self::new()
}
}
impl FrameReorderer for NoReorderer {
fn add_frame(&mut self, fref: NAFrameRef) -> bool {
if self.fref.is_none() {
self.fref = Some(fref);
true
} else {
false
}
}
fn get_frame(&mut self) -> Option<NAFrameRef> {
let mut ret = None;
swap(&mut ret, &mut self.fref);
ret
}
fn flush(&mut self) { self.fref = None; }
fn get_last_frames(&mut self) -> Option<NAFrameRef> { None }
}
/// Frame reorderer for codecs with I/P/B frames.
#[derive(Default)]
pub struct IPBReorderer {
rframe: Option<NAFrameRef>,
bframe: Option<NAFrameRef>,
}
impl IPBReorderer {
/// Constructs a new instance of `IPBReorderer`.
pub fn new() -> Self { Self::default() }
}
impl FrameReorderer for IPBReorderer {
fn add_frame(&mut self, fref: NAFrameRef) -> bool {
if self.rframe.is_some() && self.bframe.is_some() { return false; }
let is_b = fref.get_frame_type() == FrameType::B;
if is_b && self.bframe.is_some() { return false; }
if is_b {
self.bframe = Some(fref);
} else {
std::mem::swap(&mut self.bframe, &mut self.rframe);
self.rframe = Some(fref);
}
true
}
fn get_frame(&mut self) -> Option<NAFrameRef> {
let mut ret = None;
if self.bframe.is_some() {
std::mem::swap(&mut ret, &mut self.bframe);
}
ret
}
fn flush(&mut self) {
self.rframe = None;
self.bframe = None;
}
fn get_last_frames(&mut self) -> Option<NAFrameRef> {
let mut ret = None;
if self.bframe.is_some() {
std::mem::swap(&mut ret, &mut self.bframe);
} else if self.rframe.is_some() {
std::mem::swap(&mut ret, &mut self.rframe);
}
ret
}
}
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