nihav-core/src/reorder.rs

   1 //! Output frame reordering.
   2 //!
   3 //! NihAV decoders output frames in the same order as they are put in.
   4 //! In result if you want to have frames in display order you might need some frame reorderer.
   5 //! 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.
   6 //!
   7 //! You can find out required reorderer by quering codec properties using `nihav_core::register` module.
   8 use std::mem::swap;
   9 pub use crate::frame::{FrameType, NAFrameRef};
  10
  11 /// A trait for frame reorderer.
  12 pub trait FrameReorderer {
  13     /// Stores a newly decoded frame.
  14     fn add_frame(&mut self, fref: NAFrameRef) -> bool;
  15     /// Gets the next frame to be displayed (or `None` if that is not possible).
  16     fn get_frame(&mut self) -> Option<NAFrameRef>;
  17     /// Clears all stored frames.
  18     fn flush(&mut self);
  19     /// Retrieves the last frames stored by the reorderer.
  20     fn get_last_frames(&mut self) -> Option<NAFrameRef>;
  21 }
  22
  23 /// Zero reorderer.
  24 pub struct NoReorderer {
  25     fref:   Option<NAFrameRef>,
  26 }
  27
  28 impl NoReorderer {
  29     /// Constructs a new instance of `NoReorderer`.
  30     pub fn new() -> Self {
  31         Self { fref: None }
  32     }
  33 }
  34
  35 impl FrameReorderer for NoReorderer {
  36     fn add_frame(&mut self, fref: NAFrameRef) -> bool {
  37         if self.fref.is_none() {
  38             self.fref = Some(fref);
  39             true
  40         } else {
  41             false
  42         }
  43     }
  44     fn get_frame(&mut self) -> Option<NAFrameRef> {
  45         let mut ret = None;
  46         swap(&mut ret, &mut self.fref);
  47         ret
  48     }
  49     fn flush(&mut self) { self.fref = None; }
  50     fn get_last_frames(&mut self) -> Option<NAFrameRef> { None }
  51 }
  52
  53 /// Frame reorderer for codecs with I/P/B frames.
  54 #[derive(Default)]
  55 pub struct IPBReorderer {
  56     rframe:     Option<NAFrameRef>,
  57     bframe:     Option<NAFrameRef>,
  58 }
  59
  60 impl IPBReorderer {
  61     /// Constructs a new instance of `IPBReorderer`.
  62     pub fn new() -> Self { Self::default() }
  63 }
  64
  65 impl FrameReorderer for IPBReorderer {
  66     fn add_frame(&mut self, fref: NAFrameRef) -> bool {
  67         if self.rframe.is_some() && self.bframe.is_some() { return false; }
  68         let is_b = fref.get_frame_type() == FrameType::B;
  69         if is_b && self.bframe.is_some() { return false; }
  70         if is_b {
  71             self.bframe = Some(fref);
  72         } else {
  73             std::mem::swap(&mut self.bframe, &mut self.rframe);
  74             self.rframe = Some(fref);
  75         }
  76         true
  77     }
  78     fn get_frame(&mut self) -> Option<NAFrameRef> {
  79         let mut ret = None;
  80         if self.bframe.is_some() {
  81             std::mem::swap(&mut ret, &mut self.bframe);
  82         }
  83         ret
  84     }
  85     fn flush(&mut self) {
  86         self.rframe = None;
  87         self.bframe = None;
  88     }
  89     fn get_last_frames(&mut self) -> Option<NAFrameRef> {
  90         let mut ret = None;
  91         if self.bframe.is_some() {
  92             std::mem::swap(&mut ret, &mut self.bframe);
  93         } else if self.rframe.is_some() {
  94             std::mem::swap(&mut ret, &mut self.rframe);
  95         }
  96         ret
  97     }
  98 }
  99