Enum ChannelAssignment 

pub enum ChannelAssignment {
    Independent(Independent),
    LeftSide,
    SideRight,
    MidSide,
}

How the channels are assigned in a FLAC frame

Bits	Channel Assingment
0000	1 mono channel
0001	2 independent channels
0010	3 independent channels
0011	4 independent channels
0100	5 independent channels
0101	6 independent channels
0110	7 independent channels
0111	8 independent channels
1000	left channel, side channel
1001	side channel, right channel
1010	mid channel, side channel
1011	invalid channel assignment
1100	invalid channel assignment
1101	invalid channel assignment
1110	invalid channel assignment
1111	invalid channel assignment

Example

use flac_codec::stream::{ChannelAssignment, Independent};
use bitstream_io::{BitReader, BitRead, BigEndian};

let data: &[u8] = &[
    0b0000_100_0,             // channels + bps + pad
];

let mut r = BitReader::endian(data, BigEndian);
assert_eq!(
    r.parse::<ChannelAssignment>().unwrap(),
    ChannelAssignment::Independent(Independent::Mono),
);

The samples in the side channel can be calculated like:

sideᵢ = leftᵢ - rightᵢ

This requires that the side channel have one additional bit-per-sample during decoding, since the difference between the left and right channels could overflow if the two are at opposite extremes.

And with a bit of math, we can see that:

rightᵢ = leftᵢ - sideᵢ

or:

leftᵢ = sideᵢ + rightᵢ

For transforming left-side and side-right assignments back to left-right for output.

The samples in the mid channel can be calculated like:

midᵢ = (leftᵢ + rightᵢ) ÷ 2

Mid-side assignment can be restored to left-right like:

sumᵢ = midᵢ × 2 + |sideᵢ| % 2

leftᵢ = (sumᵢ + sideᵢ) ÷ 2

rightᵢ = (sumᵢ - sideᵢ) ÷ 2

The mid channel does not require any additional bits to decode, since the average cannot exceed either channel.

Variants

Independent(Independent)

Channels are stored independently

LeftSide

Channel 0 is stored verbatim, channel 1 derived from both

SideRight

Channel 0 is derived from both, channel 1 is stored verbatim

MidSide

Channel 0 is averaged from both, channel 1 is derived from both

Implementations

impl ChannelAssignment

pub fn count(&self) -> u8

Returns total number of channels defined by assignment

Trait Implementations

impl Clone for ChannelAssignment

fn clone(&self) -> ChannelAssignment

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ChannelAssignment

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

Formats the value using the given formatter.

impl Display for ChannelAssignment

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

Formats the value using the given formatter.

impl FromBitStream for ChannelAssignment

type Error = Error

Error generated during parsing, such as io::Error

fn from_reader<R: BitRead + ?Sized>(r: &mut R) -> Result<Self, Error>

Parse Self from reader

impl PartialEq for ChannelAssignment

fn eq(&self, other: &ChannelAssignment) -> 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 ToBitStream for ChannelAssignment

type Error = Error

Error generated during building, such as io::Error

fn to_writer<W: BitWrite + ?Sized>(&self, w: &mut W) -> Result<(), Error>

Generate self to writer

fn bits<C>(&self) -> Result<C, Self::Error>

where C: Counter, Self: Sized,

Returns length of self in bits, if possible

fn bits_len<C, E>(&self) -> Result<C, Self::Error>

where C: Counter, E: Endianness, Self: Sized,

👎Deprecated since 4.0.0: use of bits() is preferred

Returns total length of self, if possible

impl Copy for ChannelAssignment

impl Eq for ChannelAssignment

impl StructuralPartialEq for ChannelAssignment