Show Existing Frames

Every odd frame is a show_existing_frame.
xiph · Feb 8, 2018 · becced1 · becced1
1 parent a2d8fae
commit becced1
Show file tree

Hide file tree

Showing 2 changed files with 14 additions and 3 deletions.
diff --git a/src/bin/rav1e.rs b/src/bin/rav1e.rs
@@ -21,6 +21,7 @@ fn main() {
             break;
         }
         fi.number += 1;
+        fi.show_existing_frame = fi.number % 2 == 1;
         if fi.number == files.limit {
             break;
         }

diff --git a/src/lib.rs b/src/lib.rs
@@ -88,6 +88,7 @@ pub struct FrameInvariants {
     pub sb_height: usize,
     pub number: u64,
     pub ftype: FrameType,
+    pub show_existing_frame: bool,
 }
 
 impl FrameInvariants {
@@ -99,7 +100,8 @@ impl FrameInvariants {
             sb_width: (width+63)/64,
             sb_height: (height+63)/64,
             number: 0,
-            ftype: FrameType::KEY
+            ftype: FrameType::KEY,
+            show_existing_frame: false,
         }
     }
 }
@@ -205,6 +207,12 @@ fn write_uncompressed_header(packet: &mut Write, sequence: &Sequence, fi: &Frame
     let mut uch = BitWriter::<BE>::new(packet);
     uch.write(2,2)?; // frame type
     uch.write(2,sequence.profile)?; // profile 0
+    if fi.show_existing_frame {
+        uch.write_bit(true)?; // show_existing_frame=1
+        uch.write(3,0)?; // show last frame
+        uch.byte_align()?;
+        return Ok(());
+    }
     uch.write_bit(false)?; // show_existing_frame=0
     uch.write_bit(false)?; // keyframe
     uch.write_bit(true)?; // show frame
@@ -367,8 +375,10 @@ fn encode_tile(fi: &FrameInvariants, fs: &mut FrameState) -> Vec<u8> {
 fn encode_frame(sequence: &Sequence, fi: &FrameInvariants, fs: &mut FrameState) -> Vec<u8> {
     let mut packet = Vec::new();
     write_uncompressed_header(&mut packet, sequence, fi).unwrap();
-    let tile = encode_tile(fi, fs);
-    packet.write(&tile).unwrap();
+    if !fi.show_existing_frame {
+        let tile = encode_tile(fi, fs);
+        packet.write(&tile).unwrap();
+    }
     packet
 }