rav1r 0.1.0

AV1 encoder derived from rav1e
Documentation 
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// Copyright (c) 2022-2022, The rav1e contributors. All rights reserved
//
// This source code is subject to the terms of the BSD 2 Clause License and
// the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
// was not distributed with this source code in the LICENSE file, you can
// obtain it at www.aomedia.org/license/software. If the Alliance for Open
// Media Patent License 1.0 was not distributed with this source code in the
// PATENTS file, you can obtain it at www.aomedia.org/license/patent.

//! Film grain types, inlined from `av1-grain` 0.2.5.
//!
//! `NOTICE` records the origin.

use arrayvec::ArrayVec;

/// The max number of luma scaling points for grain synthesis
pub const NUM_Y_POINTS: usize = 14;
/// The max number of scaling points per chroma plane for grain synthesis
pub const NUM_UV_POINTS: usize = 10;
/// The max number of luma coefficients for grain synthesis
pub const NUM_Y_COEFFS: usize = 24;
/// The max number of coefficients per chroma plane for grain synthesis
pub const NUM_UV_COEFFS: usize = 25;

/// A randomly generated u16 to be used as a starting random seed
/// for grain synthesis. The idea behind using a constant random seed
/// is so that encodes are deterministic and reproducible.
pub const DEFAULT_GRAIN_SEED: u16 = 10956;

/// Luma scaling points, as cutoff and scale factor pairs.
pub type ScalingPoints = ArrayVec<[u8; 2], NUM_Y_POINTS>;

/// Specifies parameters for enabling decoder-side grain synthesis for
/// a segment of video from `start_time` to `end_time`.
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(
  feature = "serialize",
  derive(serde::Deserialize, serde::Serialize)
)]
pub struct GrainTableSegment {
  /// The beginning timestamp of this segment, in 10,000,000ths of a second.
  pub start_time: u64,
  /// The ending timestamp of this segment, not inclusive, in 10,000,000ths of
  /// a second.
  pub end_time: u64,

  /// Values for the cutoffs and scale factors for luma scaling points
  pub scaling_points_y: ArrayVec<[u8; 2], NUM_Y_POINTS>,
  /// Values for the cutoffs and scale factors for Cb scaling points
  pub scaling_points_cb: ArrayVec<[u8; 2], NUM_UV_POINTS>,
  /// Values for the cutoffs and scale factors for Cr scaling points
  pub scaling_points_cr: ArrayVec<[u8; 2], NUM_UV_POINTS>,

  /// Determines the range and quantization step of the standard deviation
  /// of film grain.
  ///
  /// Accepts values between `8..=11`.
  pub scaling_shift: u8,

  /// A factor specifying how many AR coefficients are provided,
  /// based on the forumla `coeffs_len = (2 * ar_coeff_lag * (ar_coeff_lag +
  /// 1))`.
  ///
  /// Accepts values between `0..=3`.
  pub ar_coeff_lag: u8,
  /// Values for the AR coefficients for luma scaling points
  pub ar_coeffs_y: ArrayVec<i8, NUM_Y_COEFFS>,
  /// Values for the AR coefficients for Cb scaling points
  pub ar_coeffs_cb: ArrayVec<i8, NUM_UV_COEFFS>,
  /// Values for the AR coefficients for Cr scaling points
  pub ar_coeffs_cr: ArrayVec<i8, NUM_UV_COEFFS>,
  /// Shift value: Specifies the range of acceptable AR coefficients
  /// 6: [-2, 2)
  /// 7: [-1, 1)
  /// 8: [-0.5, 0.5)
  /// 9: [-0.25, 0.25)
  pub ar_coeff_shift: u8,
  /// Multiplier to the grain strength of the Cb plane
  pub cb_mult: u8,
  /// Multiplier to the grain strength of the Cb plane inherited from the luma
  /// plane
  pub cb_luma_mult: u8,
  /// A base value for the Cb plane grain
  pub cb_offset: u16,
  /// Multiplier to the grain strength of the Cr plane
  pub cr_mult: u8,
  /// Multiplier to the grain strength of the Cr plane inherited from the luma
  /// plane
  pub cr_luma_mult: u8,
  /// A base value for the Cr plane grain
  pub cr_offset: u16,

  /// Whether film grain blocks should overlap or not
  pub overlap_flag: bool,
  /// Scale chroma grain from luma instead of providing chroma scaling points
  pub chroma_scaling_from_luma: bool,
  /// Specifies how much the Gaussian random numbers should be scaled down
  /// during the grain synthesis process.
  pub grain_scale_shift: u8,
  /// Random seed used for generating grain
  pub random_seed: u16,
}

/// Settings and video data defining how to generate the film grain params.
#[derive(Debug, Clone, Copy)]
pub struct NoiseGenArgs {
  /// The photon noise level, as an ISO setting.
  pub iso_setting: u32,
  /// The frame width in pixels.
  pub width: u32,
  /// The frame height in pixels.
  pub height: u32,
  /// The transfer function of the video.
  pub transfer_function: TransferFunction,
  /// Whether chroma planes receive grain.
  pub chroma_grain: bool,
  /// The random seed. `None` uses [`DEFAULT_GRAIN_SEED`].
  pub random_seed: Option<u16>,
}

/// The transfer function that photon noise generation assumes.
#[allow(clippy::upper_case_acronyms)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum TransferFunction {
  /// For SDR content
  BT1886,
  /// For HDR content
  SMPTE2084,
}