Enum LPCFilter

#[repr(u8)]
pub enum LPCFilter {
    Zero = 0,
    One = 1,
    Two = 2,
    Three = 3,
}

Linear predictive coding (LPC) filters used by the BRR format. Filters are specified per BRR block.

The four filters all at maximum use the last two samples (“t-1” and “t-2”) in addition to the current sample to compute the output sample. The coefficient for the current sample, after shifting, is 1. For each filter, the other coefficients are:

ff	“t-1” factor	“t-2” factor	explanation
0	0	0	verbatim samples
1	15/16 ~ 1	0	delta/differential coding
2	61/32 ~ 2	-15/16 ~ -1	almost polynomial order 2 predictor
3	115/64 ~ 2	-13/16 ~ -1	???

Variants

Zero = 0

Filter 0, verbatim samples.

One = 1

Filter 1, differential coding.

Two = 2

Filter 2, something extremely close to polynomial order 2 predictive coding (which would be s[t] + 2* s[t-1] - s[t-2]).

Three = 3

Filter 3, again very close to polynomial order 2 predictive coding but more off than filter 2. I can’t make sense of this one.

Implementations

impl LPCFilter

pub fn coefficient(self) -> [fn(i16) -> i16; 2]

Return the coefficients used by this filter. The first coefficient is for the last sample, while the second coefficient is for the second-to-last sample.

pub const fn all_filters() -> [Self; 4]

Return all possible filters.

pub const fn coefficient_0(_: i16) -> i16

• 0

pub const fn coefficient_15_16(i: i16) -> i16

• 15/16

pub const fn coefficient_negative_15_16(i: i16) -> i16

• -15/16

pub const fn coefficient_61_32(i: i16) -> i16

• 61/32

pub const fn coefficient_115_64(i: i16) -> i16

• 115/64

pub const fn coefficient_negative_13_16(i: i16) -> i16

• -13/16

Trait Implementations

impl Clone for LPCFilter

fn clone(&self) -> LPCFilter

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for LPCFilter

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for LPCFilter

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl FromPrimitive for LPCFilter

fn from_i64(n: i64) -> Option<Self>

Converts an i64 to return an optional value of this type. If the value cannot be represented by this type, then None is returned.

fn from_u64(n: u64) -> Option<Self>

Converts an u64 to return an optional value of this type. If the value cannot be represented by this type, then None is returned.

fn from_isize(n: isize) -> Option<Self>

Converts an isize to return an optional value of this type. If the value cannot be represented by this type, then None is returned.

fn from_i8(n: i8) -> Option<Self>

Converts an i8 to return an optional value of this type. If the value cannot be represented by this type, then None is returned.

fn from_i16(n: i16) -> Option<Self>

Converts an i16 to return an optional value of this type. If the value cannot be represented by this type, then None is returned.

fn from_i32(n: i32) -> Option<Self>

Converts an i32 to return an optional value of this type. If the value cannot be represented by this type, then None is returned.

fn from_i128(n: i128) -> Option<Self>

Converts an i128 to return an optional value of this type. If the value cannot be represented by this type, then None is returned.

fn from_usize(n: usize) -> Option<Self>

Converts a usize to return an optional value of this type. If the value cannot be represented by this type, then None is returned.

fn from_u8(n: u8) -> Option<Self>

Converts an u8 to return an optional value of this type. If the value cannot be represented by this type, then None is returned.

fn from_u16(n: u16) -> Option<Self>

Converts an u16 to return an optional value of this type. If the value cannot be represented by this type, then None is returned.

fn from_u32(n: u32) -> Option<Self>

Converts an u32 to return an optional value of this type. If the value cannot be represented by this type, then None is returned.

fn from_u128(n: u128) -> Option<Self>

Converts an u128 to return an optional value of this type. If the value cannot be represented by this type, then None is returned.

fn from_f32(n: f32) -> Option<Self>

Converts a f32 to return an optional value of this type. If the value cannot be represented by this type, then None is returned.

fn from_f64(n: f64) -> Option<Self>

Converts a f64 to return an optional value of this type. If the value cannot be represented by this type, then None is returned.

impl PartialEq for LPCFilter

fn eq(&self, other: &LPCFilter) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for LPCFilter

impl Eq for LPCFilter

impl StructuralPartialEq for LPCFilter