codec/av1/parser: switch buffer_delay_length_minus_1 to u8

This member is read from 5 bits. This removes the need for
potentially-failing type conversions.

src/codec/av1/parser.rs

@@ -243,7 +243,7 @@ pub struct TimingInfo {
 pub struct DecoderModelInfo {
     /// Plus 1 specifies the length of the decoder_buffer_delay and the
     /// encoder_buffer_delay syntax elements, in bits.
-    pub buffer_delay_length_minus_1: u32,
+    pub buffer_delay_length_minus_1: u8,
     /// The number of time units of a decoding clock operating at the frequency
     /// time_scale Hz that corresponds to one increment of a clock tick counter:
     pub num_units_in_decoding_tick: u32,
@@ -1679,17 +1679,17 @@ impl Parser {
     fn parse_operating_parameters_info(
         opi: &mut OperatingPoint,
         r: &mut Reader,
-        buffer_delay_length_minus_1: u32,
+        buffer_delay_length_minus_1: u8,
     ) -> anyhow::Result<()> {
-        let n = u8::try_from(buffer_delay_length_minus_1 + 1).unwrap();
+        let n = buffer_delay_length_minus_1 + 1;
         opi.decoder_buffer_delay = r.read_bits(n)?;
         opi.encoder_buffer_delay = r.read_bits(n)?;
         opi.low_delay_mode_flag = r.read_bit()?;
         Ok(())
     }
 
     fn parse_decoder_model_info(dmi: &mut DecoderModelInfo, r: &mut Reader) -> anyhow::Result<()> {
-        dmi.buffer_delay_length_minus_1 = r.read_bits(5)?;
+        dmi.buffer_delay_length_minus_1 = r.read_bits(5)? as u8;
         dmi.num_units_in_decoding_tick = r.read_bits(32)?;
         dmi.buffer_removal_time_length_minus_1 = r.read_bits(5)?;
         dmi.frame_presentation_time_length_minus_1 = r.read_bits(5)?;

src/codec/av1/synthesizer.rs

@@ -592,7 +592,7 @@ where
     fn operating_parameters_info(&mut self, i: usize) -> SynthesizerResult<()> {
         let op = &self.obu.operating_points[i];
 
-        let n = usize::try_from(self.obu.decoder_model_info.buffer_delay_length_minus_1)? + 1;
+        let n = usize::from(self.obu.decoder_model_info.buffer_delay_length_minus_1) + 1;
         self.f(n, op.decoder_buffer_delay)?;
         self.f(n, op.encoder_buffer_delay)?;
         self.f(1, op.low_delay_mode_flag)?;