Enum ProgressiveMode 

pub enum ProgressiveMode {
    Single,
    QuantizedAcFullAc,
    DcVlfLfAc,
}

Progressive encoding mode for VarDCT.

Progressive encoding splits AC coefficients across multiple passes by reducing precision. Decoders can render a coarse preview after early passes, improving user experience for web delivery.

The shift mechanism works by right-shifting quantized coefficients before encoding in early passes. The decoder left-shifts and accumulates, so the final result is exact (lossless reconstruction of the quantized coefficients).

Variants

Single

Single pass (default). No progressive rendering.

QuantizedAcFullAc

2-pass quantized progressive.

• Pass 0: All AC coefficients right-shifted by 1 bit (coarse)
• Pass 1: Residual at full precision

Provides quick 2x-downsampled preview, then full quality refinement.

DcVlfLfAc

3-pass progressive (DC/VLF → LF → Full AC).

• Pass 0: All AC coefficients right-shifted by 2 bits (very coarse, 8x downsample hint)
• Pass 1: Residual right-shifted by 1 bit (medium, 4x downsample hint)
• Pass 2: Final residual at full precision

Provides staged refinement: blurry preview → sharper → final.

Trait Implementations

impl Clone for ProgressiveMode

fn clone(&self) -> ProgressiveMode

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ProgressiveMode

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

Formats the value using the given formatter.

impl Default for ProgressiveMode

fn default() -> ProgressiveMode

Returns the “default value” for a type.

impl PartialEq for ProgressiveMode

fn eq(&self, other: &ProgressiveMode) -> 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 ProgressiveMode

impl Eq for ProgressiveMode

impl StructuralPartialEq for ProgressiveMode