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//! HEVC PPS fields needed to fill VA-API's HEVC decode parameter buffers (ITU-T H.265 §
//! 7.3.2.3.1). Starts from `vulkan::hevc_params::HevcPps::parse` (cited, not imported — see
//! `adr/linux/0003-vaapi-hevc-p-slice-dpb.md` § Alternatives Considered), reusing its parse
//! sequence verbatim through `deblocking_filter_control_present_flag`, then **extends** it with
//! a real PPS-parsing tail that porting source never needed (Vulkan Video hands the raw
//! bitstream to the hardware decoder, which parses its own slice/PPS syntax; this crate's own
//! app-must-parse VA-API model has no such luxury — same asymmetry
//! [`super::sps`]/[`super::pps`] (H.264) already established):
//!
//! ```text
//! pps_scaling_list_data_present_flag // if 1: scaling_list_data() — rejected, not parsed
//! lists_modification_present_flag // retained: needed for VASliceParsingFields
//! log2_parallel_merge_level_minus2 // retained: real PictureParameterBufferHEVC field
//! slice_segment_header_extension_present_flag // if 1: extra slice-header bits — rejected
//! pps_extension_present_flag // if 1: range/SCC/etc extensions — rejected
//! ```
//!
//! Scope matches [`super::hevc_sps::HevcSps`] and this ADR: single slice group / single tile, no
//! WPP, no scaling lists, no deblocking-control override, no slice-header extension, no PPS
//! range/SCC extensions.
#![forbid(unsafe_code)]
#![allow(
clippy::cast_possible_truncation,
reason = "every count here comes from an Exp-Golomb-decoded HEVC syntax element, always \
small in practice — mirrors vulkan::hevc_params's identical allow"
)]
use crate::DecodeError;
use mediaway_sw::h264::BitReader;
/// Parsed HEVC PPS fields this crate's VA-API decode session needs.
#[allow(
clippy::struct_excessive_bools,
reason = "each bool is a real, independent ITU-T H.265 PPS flag that must be echoed into \
PictureParameterBufferHEVC/SliceParsingFields exactly as signaled — mirrors \
vulkan::HevcPps's identical allow"
)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(super) struct HevcPps {
/// `pps_pic_parameter_set_id` — checked against each slice's own
/// `slice_pic_parameter_set_id` before decode (mirrors this crate's H.264 sibling's
/// identical `pic_parameter_set_id` consistency check).
pub(super) pps_pic_parameter_set_id: u32,
/// `dependent_slice_segments_enabled_flag`. Every *accepted* slice this crate decodes has
/// `dependent_slice_segment_flag == 0` (single slice per picture, enforced by
/// [`super::hevc_slice`]), but the PPS may still legally enable the capability without any
/// given slice using it — echoed honestly regardless.
pub(super) dependent_slice_segments_enabled_flag: bool,
/// `output_flag_present_flag` — gates `pic_output_flag` in the slice segment header.
pub(super) output_flag_present_flag: bool,
/// `num_extra_slice_header_bits` — count of `slice_reserved_flag[i]` bits to skip in the
/// slice segment header.
pub(super) num_extra_slice_header_bits: u32,
/// `sign_data_hiding_enabled_flag`.
pub(super) sign_data_hiding_enabled_flag: bool,
/// `cabac_init_present_flag`.
pub(super) cabac_init_present_flag: bool,
/// `num_ref_idx_l0_default_active_minus1 + 1`.
pub(super) num_ref_idx_l0_default_active: u32,
/// `num_ref_idx_l1_default_active_minus1 + 1`.
pub(super) num_ref_idx_l1_default_active: u32,
/// `init_qp_minus26 + 26`.
pub(super) init_qp: i32,
/// `constrained_intra_pred_flag`.
pub(super) constrained_intra_pred_flag: bool,
/// `transform_skip_enabled_flag` — gates a per-TU bit; a mismatch desyncs CABAC parsing.
pub(super) transform_skip_enabled_flag: bool,
/// `cu_qp_delta_enabled_flag` — gates per-CU-group bits; a mismatch desyncs CABAC parsing.
pub(super) cu_qp_delta_enabled_flag: bool,
/// `diff_cu_qp_delta_depth` — only meaningful when `cu_qp_delta_enabled_flag` is set.
pub(super) diff_cu_qp_delta_depth: u32,
/// `pps_cb_qp_offset` (`se(v)`).
pub(super) pps_cb_qp_offset: i32,
/// `pps_cr_qp_offset` (`se(v)`).
pub(super) pps_cr_qp_offset: i32,
/// `pps_slice_chroma_qp_offsets_present_flag` — gates `slice_cb_qp_offset`/
/// `slice_cr_qp_offset` bits in every slice header.
pub(super) pps_slice_chroma_qp_offsets_present_flag: bool,
/// `weighted_pred_flag` (P slices only). This crate does not parse `pred_weight_table()`, so
/// [`super::hevc_slice::HevcSliceSegmentHeader::parse`] rejects any P slice referencing a
/// PPS with this set.
pub(super) weighted_pred_flag: bool,
/// `weighted_bipred_flag` (B slices only — unreachable, B-slices rejected upstream).
pub(super) weighted_bipred_flag: bool,
/// `transquant_bypass_enabled_flag` — gates a bit at the start of every `coding_unit()`.
pub(super) transquant_bypass_enabled_flag: bool,
/// `pps_loop_filter_across_slices_enabled_flag` — gates
/// `slice_loop_filter_across_slices_enabled_flag` in every slice header (see
/// [`super::hevc_slice`]).
pub(super) pps_loop_filter_across_slices_enabled_flag: bool,
/// `lists_modification_present_flag` — a real `VASliceParsingFields` value the driver-facing
/// struct must carry honestly. Functionally inert for this ADR's scope, since
/// `NumPicTotalCurr` is always `<= 1` for any stream this crate accepts (`ref_pic_lists_modification()`
/// is provably unreachable — see [`super::hevc_slice`]'s module doc).
pub(super) lists_modification_present_flag: bool,
/// `log2_parallel_merge_level_minus2` — a real `PictureParameterBufferHEVC` top-level field
/// with no Vulkan-side decode equivalent need (this ADR's own PPS-parsing extension).
pub(super) log2_parallel_merge_level_minus2: u32,
}
impl HevcPps {
/// Parse a PPS RBSP (2-byte NAL header already stripped).
///
/// # Errors
///
/// [`DecodeError::Unsupported`] when `num_slice_groups_minus1 > 0` (tiles/FMO/ASO, folded
/// into this crate's own `tiles_enabled_flag`/`entropy_coding_sync_enabled_flag` checks
/// below since HEVC's own PPS carries them directly, unlike H.264's separate
/// `num_slice_groups_minus1`), `tiles_enabled_flag == 1`, `entropy_coding_sync_enabled_flag
/// == 1` (WPP), `deblocking_filter_control_present_flag == 1`,
/// `pps_scaling_list_data_present_flag == 1`, `slice_segment_header_extension_present_flag
/// == 1`, or `pps_extension_present_flag == 1` — all out of scope, per the module doc.
/// Other [`DecodeError::InvalidInput`] on truncated/overflowing data.
#[allow(
clippy::too_many_lines,
reason = "linear ITU-T H.265 § 7.3.2.3.1 syntax-element sequence through the fields this \
crate's decode session needs, including this ADR's own new PPS-parsing tail \
(see module doc) — mirrors vulkan::HevcPps::parse's identical allow"
)]
pub(super) fn parse(rbsp: &[u8]) -> Result<Self, DecodeError> {
let mut r = BitReader::new(rbsp);
let map_err = |_| DecodeError::InvalidInput;
let pps_pic_parameter_set_id = r.read_ue().map_err(map_err)?;
let _pps_seq_parameter_set_id = r.read_ue().map_err(map_err)?;
let dependent_slice_segments_enabled_flag = r.read_bit().map_err(map_err)? != 0;
let output_flag_present_flag = r.read_bit().map_err(map_err)? != 0;
let num_extra_slice_header_bits = r.read_bits(3).map_err(map_err)?;
let sign_data_hiding_enabled_flag = r.read_bit().map_err(map_err)? != 0;
let cabac_init_present_flag = r.read_bit().map_err(map_err)? != 0;
let num_ref_idx_l0_default_active = r
.read_ue()
.map_err(map_err)?
.checked_add(1)
.ok_or(DecodeError::InvalidInput)?;
let num_ref_idx_l1_default_active = r
.read_ue()
.map_err(map_err)?
.checked_add(1)
.ok_or(DecodeError::InvalidInput)?;
let init_qp_minus26 = r.read_se().map_err(map_err)?;
let constrained_intra_pred_flag = r.read_bit().map_err(map_err)? != 0;
let transform_skip_enabled_flag = r.read_bit().map_err(map_err)? != 0;
let cu_qp_delta_enabled_flag = r.read_bit().map_err(map_err)? != 0;
let diff_cu_qp_delta_depth = if cu_qp_delta_enabled_flag {
r.read_ue().map_err(map_err)?
} else {
0
};
let pps_cb_qp_offset = r.read_se().map_err(map_err)?;
let pps_cr_qp_offset = r.read_se().map_err(map_err)?;
let pps_slice_chroma_qp_offsets_present_flag = r.read_bit().map_err(map_err)? != 0;
let weighted_pred_flag = r.read_bit().map_err(map_err)? != 0;
let weighted_bipred_flag = r.read_bit().map_err(map_err)? != 0;
let transquant_bypass_enabled_flag = r.read_bit().map_err(map_err)? != 0;
let tiles_enabled_flag = r.read_bit().map_err(map_err)? != 0;
let entropy_coding_sync_enabled_flag = r.read_bit().map_err(map_err)? != 0;
if tiles_enabled_flag {
return Err(DecodeError::Unsupported);
}
if entropy_coding_sync_enabled_flag {
return Err(DecodeError::Unsupported);
}
// `pps_loop_filter_across_slices_enabled_flag` gates a real slice-header bit whenever
// SAO or (undisabled) deblocking is active — see `super::hevc_slice`'s module doc.
let pps_loop_filter_across_slices_enabled_flag = r.read_bit().map_err(map_err)? != 0;
let deblocking_filter_control_present_flag = r.read_bit().map_err(map_err)? != 0;
if deblocking_filter_control_present_flag {
return Err(DecodeError::Unsupported);
}
// This ADR's own new PPS-parsing tail (see module doc) — real ITU-T H.265 § 7.3.2.3.1
// syntax `vulkan::hevc_params::HevcPps::parse` never reads at all.
let pps_scaling_list_data_present_flag = r.read_bit().map_err(map_err)? != 0;
if pps_scaling_list_data_present_flag {
return Err(DecodeError::Unsupported);
}
let lists_modification_present_flag = r.read_bit().map_err(map_err)? != 0;
let log2_parallel_merge_level_minus2 = r.read_ue().map_err(map_err)?;
let slice_segment_header_extension_present_flag = r.read_bit().map_err(map_err)? != 0;
if slice_segment_header_extension_present_flag {
return Err(DecodeError::Unsupported);
}
let pps_extension_present_flag = r.read_bit().map_err(map_err)? != 0;
if pps_extension_present_flag {
return Err(DecodeError::Unsupported);
}
// rbsp_trailing_bits() follows — not needed for this crate's decode path.
let init_qp = init_qp_minus26
.checked_add(26)
.ok_or(DecodeError::InvalidInput)?;
Ok(Self {
pps_pic_parameter_set_id,
dependent_slice_segments_enabled_flag,
output_flag_present_flag,
num_extra_slice_header_bits,
sign_data_hiding_enabled_flag,
cabac_init_present_flag,
num_ref_idx_l0_default_active,
num_ref_idx_l1_default_active,
init_qp,
constrained_intra_pred_flag,
transform_skip_enabled_flag,
cu_qp_delta_enabled_flag,
diff_cu_qp_delta_depth,
pps_cb_qp_offset,
pps_cr_qp_offset,
pps_slice_chroma_qp_offsets_present_flag,
weighted_pred_flag,
weighted_bipred_flag,
transquant_bypass_enabled_flag,
pps_loop_filter_across_slices_enabled_flag,
lists_modification_present_flag,
log2_parallel_merge_level_minus2,
})
}
}
#[cfg(test)]
#[path = "hevc_pps_tests.rs"]
mod tests;