codec/av1/parser: turn max_frame_width_minus_1 into u16

This member is read from 16 bits max. Doing so allows us to avoid some
type conversions and optimize the code.

Author: Gnurou

src/codec/av1/parser.rs

@@ -398,7 +398,7 @@ pub struct SequenceHeaderObu {
     pub frame_height_bits_minus_1: u8,
     /// Specifies the maximum frame width minus 1 for the frames represented by
     /// this sequence header.
-    pub max_frame_width_minus_1: u32,
+    pub max_frame_width_minus_1: u16,
     /// Specifies the maximum frame height minus 1 for the frames represented by
     /// this sequence header.
     pub max_frame_height_minus_1: u32,
@@ -1393,7 +1393,7 @@ impl Parser {
             let n = seq.frame_height_bits_minus_1 + 1;
             fh.frame_height = r.read_bits(n)? + 1;
         } else {
-            fh.frame_width = seq.max_frame_width_minus_1 + 1;
+            fh.frame_width = seq.max_frame_width_minus_1 as u32 + 1;
             fh.frame_height = seq.max_frame_height_minus_1 + 1;
         }
 
@@ -1823,7 +1823,8 @@ impl Parser {
 
         s.frame_width_bits_minus_1 = r.read_bits(4)? as u8;
         s.frame_height_bits_minus_1 = r.read_bits(4)? as u8;
-        s.max_frame_width_minus_1 = r.read_bits(s.frame_width_bits_minus_1 + 1)?;
+        // frame_width_bits_minus_1 has been read from 4 bits, meaning we can read 16 bits at most.
+        s.max_frame_width_minus_1 = r.read_bits(s.frame_width_bits_minus_1 + 1)? as u16;
         s.max_frame_height_minus_1 = r.read_bits(s.frame_height_bits_minus_1 + 1)?;
         if s.reduced_still_picture_header {
             s.frame_id_numbers_present_flag = false;

src/codec/av1/synthesizer.rs

@@ -963,7 +963,7 @@ where
             let n = sequence.frame_height_bits_minus_1 as usize + 1;
             self.f(n, self.obu.frame_height - 1)?;
         } else {
-            if self.obu.frame_width != sequence.max_frame_width_minus_1 + 1 {
+            if self.obu.frame_width != sequence.max_frame_width_minus_1 as u32 + 1 {
                 self.invalid_element_value("FrameWidth")?;
             }
             if self.obu.frame_height != sequence.max_frame_height_minus_1 + 1 {
@@ -1710,7 +1710,7 @@ mod tests {
 
             frame_width_bits_minus_1: 16 - 1,
             frame_height_bits_minus_1: 16 - 1,
-            max_frame_width_minus_1: WIDTH - 1,
+            max_frame_width_minus_1: (WIDTH - 1) as u16,
             max_frame_height_minus_1: HEIGHT - 1,
 
             seq_force_integer_mv: SELECT_INTEGER_MV as u32,

src/decoder/stateless/av1.rs

@@ -436,7 +436,7 @@ where
                         log::debug!(
                             "Found new sequence, resolution: {:?}, profile: {:?}, bit depth: {:?}",
                             Resolution::from((
-                                sequence.max_frame_width_minus_1 + 1,
+                                sequence.max_frame_width_minus_1 as u32 + 1,
                                 sequence.max_frame_height_minus_1 + 1
                             )),
                             sequence.seq_profile,

src/decoder/stateless/av1/vaapi.rs

@@ -93,7 +93,7 @@ impl VaStreamInfo for &Rc<SequenceHeaderObu> {
 
     fn coded_size(&self) -> (u32, u32) {
         (
-            self.max_frame_width_minus_1 + 1,
+            self.max_frame_width_minus_1 as u32 + 1,
             self.max_frame_height_minus_1 + 1,
         )
     }
@@ -513,7 +513,7 @@ impl<M: SurfaceMemoryDescriptor + 'static> StatelessAV1DecoderBackend for VaapiB
                 /* The spec mandates a 2:1 or 1.5:1 ratio, let's go with 2:1 to
                  * accomodate the other case. See 6.7.5 in the spec */
                 let layers = (0..=highest_layer).map(|layer| Resolution {
-                    width: (sequence.max_frame_width_minus_1 + 1) / (layer + 1),
+                    width: (sequence.max_frame_width_minus_1 as u32 + 1) / (layer + 1),
                     height: (sequence.max_frame_height_minus_1 + 1) / (layer + 1),
                 });
 

src/encoder/stateless/av1/predictor.rs

@@ -92,7 +92,7 @@ impl<Picture, Reference> LowDelayAV1<Picture, Reference> {
             frame_height_bits_minus_1: (1 << 4) - 1,
 
             // Current resolution is the maximum resolution
-            max_frame_width_minus_1: width - 1,
+            max_frame_width_minus_1: (width - 1) as u16,
             max_frame_height_minus_1: height - 1,
 
             seq_force_integer_mv: SELECT_INTEGER_MV as u32,

src/encoder/stateless/av1/vaapi.rs

@@ -716,7 +716,7 @@ mod tests {
 
             frame_width_bits_minus_1: 16 - 1,
             frame_height_bits_minus_1: 16 - 1,
-            max_frame_width_minus_1: WIDTH - 1,
+            max_frame_width_minus_1: (WIDTH - 1) as u16,
             max_frame_height_minus_1: HEIGHT - 1,
 
             enable_order_hint: true,