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filmcraft-apv

Clean-room Advanced Professional Video (APV) decoder and encoder in pure Rust, implemented strictly from the public IETF RFC 9924 specification (Advanced Professional Video, February 2026, ISSN 2070-1721).

Layer L0: depends only on filmcraft-bitstream, thiserror, and (optional, feature threads, default on) rayon. Builds for wasm32-unknown-unknown; unsafe_code = "forbid".

API

use filmcraft_apv::*;

// Decode one APV Access Unit (or raw bitstream AU prefixed with a 32-bit au_size).
let frame: Frame = decode_frame(&au)?;
let f8 = decode_frame_with(&au, &DecodeOptions { bit_depth: Some(8), threads: true })?;
decode_frame_into(&au, &DecodeOptions::default(), &mut frame_buf)?;
let hdr: FrameHeader = probe(&au)?;

// Split a multi-AU raw .apv bitstream (RFC 9924 Appendix A).
let aus: Vec<&[u8]> = split_raw_bitstream(&raw_apv_bytes)?;

// Encode progressive intra frames.
let mut enc = Encoder::new(Profile::P422_10, 1920, 1080)?;
let au: Vec<u8> = enc.encode(&frame)?;          // Access Unit starting with 'aPv1'
let raw_au: Vec<u8> = enc.encode_raw_au(&frame)?; // Prefixed with 32-bit au_size (ISOBMFF apv1 / .apv)
let apvc: Vec<u8> = enc.decoder_config_record();  // APVDecoderConfigurationRecord payload

Specification Coverage (IETF RFC 9924)

Decoder

Access Units & PBUs (§5.3.1–5.3.3, Appendix A): Accepts both unprefixed Access Units ('aPv1' signature) and length-prefixed raw_bitstream_access_unit() packets. Parses primary (pbu_type == 1), non-primary (2), preview (25), auxiliary alpha (27), AU info (65), metadata (66), and filler (67) PBUs. PBUs or frame headers with non-zero reserved_zero_* fields are ignored per §5.3.3 and §5.3.5.
Profiles & Sampling (§9.3): All 7 standard profiles (422-10 idc 33, 422-12 idc 44, 444-10 idc 55, 444-12 idc 66, 4444-10 idc 77, 4444-12 idc 88, 400-10 idc 99) at coded bit depths 10–16, with optional output depth rescaling (8..=16).
Quantization Matrices & Tiles (§5.3.7–5.3.8, §5.3.12–5.3.14): Default flat (16) and custom per-component 8×8 quantization matrices (use_q_matrix), optional tile_size_in_fh verification, and independent per-tile, per-component byte-aligned entropy partitions. Tiles decode in parallel via rayon when threads is enabled.
Entropy Decoding (§5.3.15–5.3.16, §7.1): Adaptive Golomb-Rice / Exp-Golomb VLC decoding for abs_dc_coeff_diff, coeff_zero_run, and abs_ac_coeff_minus1 with state tracking (PrevDC, PrevDcDiff, Prev1stAcLevel, PrevLevel, PrevRun) across the 8×8 blocks of each macroblock.
Scaling & Inverse Transform (§6.3): Exact integer dequantization (levelScale = [40, 45, 51, 57, 64, 71], bdShift = BitDepth - 2) and 2-D separable 8×8 integer inverse transform using the RFC 9924 Figure 25 transMatrix. Note: in RFC 9924 §6.3.2.2, transMatrix[m][n] has row m as the frequency index (row 0 is [64; 8]) and column n as the spatial sample index, so the 1-D inverse transform evaluates sum_j transMatrix[j][i] * x[j].
Metadata (§8): Parses metadata_mdcv (payloadType == 5, Mastering Display Color Volume) and metadata_cll (payloadType == 6, Content Light-Level Information).
Robustness (§10): All size fields, tile coordinates, VLC codeword lengths, and coefficient ranges (-32768..=32767) are checked before allocation or shift. Verified by tests/fuzz.rs across thousands of mutated and random inputs.

Encoder

Progressive intra encoding for all 7 profiles (422-10, 422-12, 444-10, 444-12, 4444-10, 4444-12, 400-10).
Supports fixed qp or binary-search frame-budget rate control over forward-transformed tiles.
Emits conforming tile grids (tile_width_in_mbs >= 16, tile_height_in_mbs >= 8, TileCols, TileRows <= 20), optional custom quantization matrices, optional MDCV/CLL metadata PBUs, and APVDecoderConfigurationRecord (apvC) metadata.

Accuracy (vs FFmpeg as an External Oracle)

tests/oracle.rs encodes synthetic test patterns across all 7 profiles, odd dimensions, multiple tiles, custom asymmetric quantization matrices, and HDR metadata PBUs, then decodes the resulting .apv streams with ffmpeg -v error -xerror -f apv and compares against filmcraft_apv::decode_frame. Because APV specifies an exact integer inverse transform, filmcraft-apv is 100% bit-exact (max_diff = 0) with FFmpeg's APV decoder across every profile and test case.

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