core: replace vec.truncate(0) with vec.clear()

[nihav.git] / nihav-core / src / reorder.rs

diff --git a/nihav-core/src/reorder.rs b/nihav-core/src/reorder.rs
index fe6670c85bba2c46fc97d104a5bc15cc0d0eeda6..ebd7bdfcafa40d1196228dcda16905c9f83aa2d3 100644 (file)
--- a/nihav-core/src/reorder.rs
+++ b/nihav-core/src/reorder.rs
@@ -1,23 +1,43 @@
+//! 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() {
@@ -36,6 +56,7 @@ impl FrameReorderer for NoReorderer {
     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>,
@@ -43,6 +64,7 @@ pub struct IPBReorderer {
 }
 
 impl IPBReorderer {
+    /// Constructs a new instance of `IPBReorderer`.
     pub fn new() -> Self { Self::default() }
 }
 
@@ -81,3 +103,70 @@ impl FrameReorderer for IPBReorderer {
     }
 }
 
+/// Frame reorderer for codecs with complex I/P/B frame structure like ITU H.26x.
+#[derive(Default)]
+pub struct ComplexReorderer {
+    last_ref_dts:   Option<u64>,
+    ready_idx:      usize,
+    frames:         Vec<NAFrameRef>,
+}
+
+impl ComplexReorderer {
+    /// Constructs a new instance of `IPBReorderer`.
+    pub fn new() -> Self { Self::default() }
+}
+
+impl FrameReorderer for ComplexReorderer {
+    fn add_frame(&mut self, fref: NAFrameRef) -> bool {
+        if self.frames.len() >= 64 {
+            return false;
+        }
+        let is_ref = fref.frame_type == FrameType::I || fref.frame_type == FrameType::P;
+        if !is_ref {
+            if self.frames.is_empty() || fref.get_dts().is_none() {
+                self.frames.push(fref);
+            } else if let Some(new_dts) = fref.get_dts() {
+                let mut idx = 0;
+                for (i, frm) in self.frames.iter().enumerate() {
+                    idx = i;
+                    if let Some(dts) = frm.get_dts() {
+                        if dts > new_dts {
+                            break;
+                        }
+                    }
+                }
+                self.frames.insert(idx, fref);
+            }
+        } else {
+            for (i, frm) in self.frames.iter().enumerate() {
+                if frm.get_dts() == self.last_ref_dts {
+                    self.ready_idx = i + 1;
+                }
+            }
+            self.last_ref_dts = fref.get_dts();
+            self.frames.push(fref);
+        }
+        true
+    }
+    fn get_frame(&mut self) -> Option<NAFrameRef> {
+        if self.ready_idx > 0 {
+            self.ready_idx -= 1;
+            Some(self.frames.remove(0))
+        } else {
+            None
+        }
+    }
+    fn flush(&mut self) {
+        self.last_ref_dts = None;
+        self.ready_idx = 0;
+        self.frames.clear();
+    }
+    fn get_last_frames(&mut self) -> Option<NAFrameRef> {
+        if !self.frames.is_empty() {
+            Some(self.frames.remove(0))
+        } else {
+            None
+        }
+    }
+}
+