Crate oxideav_mjpeg 

JPEG / Motion-JPEG codec, pure Rust.

Each video packet is a standalone JPEG (one full SOI..EOI). The decoder recognises baseline (SOF0), extended-sequential (SOF1), progressive (SOF2), and lossless (SOF3) JPEGs with 4:2:0 / 4:2:2 / 4:4:4 chroma subsampling (DCT variants) and outputs MjpegFrames in the matching Yuv*P pixel format or Gray8 for 1-component streams. SOF0 and SOF1 share the same Huffman sequential scan structure at 8-bit precision; both are handled by the same scan decoder, and non-interleaved sequential scans (one SOS per component) fall back to the same coefficient-accumulator path used by the progressive decoder. Progressive scans accumulate DCT coefficients across multiple SOS segments using both spectral selection and successive approximation; the inverse DCT runs once after EOI. Restart markers (RSTn) and DRI segments are honoured on both paths. APP0..APP15 segments (JFIF, EXIF, ICC, XMP, …) are skipped without parsing. The encoder accepts the same pixel formats and produces a standalone baseline JPEG using the Annex K “typical” Huffman tables, so its output is interoperable with any compliant JPEG decoder. A progressive (SOF2) output mode is available via encoder::MjpegEncoder::set_progressive or encoder::encode_jpeg_progressive; it emits a DC-first scan followed by two per-component AC band scans (spectral selection only, Ah = Al = 0). A lossless (SOF3) grayscale output mode is available via encoder::encode_lossless_jpeg_grayscale (or MjpegEncoder::set_lossless(true) on the trait-API encoder): every precision P ∈ 2..=16 and every Annex H Table H.1 spatial predictor 1..=7 are supported, and the bitstream round-trips bit-exact through the matching SOF3 decoder.

4-component (CMYK / Adobe YCCK) JPEGs decode to packed Cmyk — the decoder inspects the APP14 Adobe transform flag to choose among plain CMYK, Adobe-inverted CMYK, and Adobe YCCK (which is colour-converted back to CMYK via BT.601 full-range YCbCr→RGB→CMY plus K inversion). The 4-component path covers both the sequential (SOF0 / SOF1) and the progressive (SOF2) scan decompositions at P = 8. 12-bit precision sequential JPEGs (SOF0/SOF1 with P=12) decode to Gray12Le / Yuv444P12Le / Yuv422P12Le / Yuv420P12Le; sample buffers stay 16-bit throughout the inverse DCT and the level shift uses 2048. Lossless JPEGs (SOF3) decode at every precision P ∈ 2..=16 via Annex H predictor reconstruction (bit-exact, no DCT). Single-component grayscale output: Gray8 at P = 8, Gray10Le / Gray12Le at P = 10/12, Gray16Le everywhere else. Three-component (RGB-class, H_i = V_i = 1) output: packed Rgb24 at P = 8, planar Gbrp10Le / Gbrp12Le / Gbrp14Le at P = 10/12/14, packed Rgb48Le at every other precision in the valid range.

Extended-sequential arithmetic (SOF9) is decoded via the Q-coder / arithmetic entropy decoder from T.81 Annex D + F.2.4. The DAC marker (Define Arithmetic Conditioning) is parsed when present; if absent the decoder uses the spec defaults (L=0, U=1) for DC / lossless conditioning and Kx=5 for AC. Progressive arithmetic (SOF10) is decoded via the same Q-coder under the T.81 §G.1.3 procedures: DC first scans reuse the §F.1.4.1 model on the point-transformed values, DC refinement bits use the fixed 0.5 estimate, AC first scans run the §F.1.4 procedure per band (Kmin = Ss, EOB = end-of-band), and AC refinement scans follow the §G.1.3.3 model (Figures G.10 / G.11, Table G.2) — at P = 8 and P = 12 with the same output shaping as the Huffman progressive (SOF2) path, 4-component CMYK / YCCK included at P = 8. Lossless arithmetic (SOF11) is decoded via the same Q-coder under the two-dimensional statistical model of §H.1.2.3 (binary decisions conditioned on the left / above difference classifications through the Figure H.2 array), covering the full Annex H surface the SOF3 path handles: every precision, every predictor, point transform and restart intervals.

Not supported (will return Error::Unsupported):

• Hierarchical (SOF5..SOF7, SOF13..SOF15) JPEGs
• 12-bit progressive 4-component JPEGs (the workspace PixelFormat enum has no 12-bit CMYK variant; P=8 4-component CMYK / YCCK is supported on both the sequential and progressive scan decompositions).

Motion-JPEG carried over RTP (RFC 2435) is supported on the decode path via rtp::JpegDepacketizer, which reassembles fragmented RTP/JPEG payloads and reconstructs the absent SOI / DQT / SOF0 / DHT / SOS / EOI marker segments (from the §3.1 main header’s Q field or an in-band §3.1.8 quantization-table header) so the result is a complete JPEG interchange stream the decoder consumes directly.

Standalone vs registry-integrated

The crate’s default registry Cargo feature pulls in oxideav-core and exposes the Decoder / Encoder trait surface, the JPEG-still container, and the registry::register / registry::register_codecs / registry::register_containers entry points. Disable the feature (default-features = false) for an oxideav-core-free build that still exposes the standalone [decoder::decode_jpeg] API plus crate-local MjpegFrame / MjpegPlane / MjpegPixelFormat / MjpegError types built only on std.

Re-exports

pub use error::MjpegError;

pub use error::Result;

pub use image::MjpegFrame;

pub use image::MjpegPixelFormat;

pub use image::MjpegPlane;

pub use jpeg::inspect::inspect_jpeg;

pub use jpeg::inspect::parse_adobe_app14;

pub use jpeg::inspect::parse_icc_profile_app2;

pub use jpeg::inspect::parse_jfif_app0;

pub use jpeg::inspect::parse_jfxx_app0;

pub use jpeg::inspect::AdobeApp14;

pub use jpeg::inspect::AdobeColorTransform;

pub use jpeg::inspect::ChromaSubsampling;

pub use jpeg::inspect::ColorHint;

pub use jpeg::inspect::IccProfileApp2Chunk;

pub use jpeg::inspect::IccProfileChunks;

pub use jpeg::inspect::InspectedComponent;

pub use jpeg::inspect::JfifApp0;

pub use jpeg::inspect::JfifUnits;

pub use jpeg::inspect::JfxxApp0;

pub use jpeg::inspect::JfxxThumbnail;

pub use jpeg::inspect::JpegInfo;

pub use jpeg::inspect::SofKind;

pub use registry::register;

pub use registry::register_codecs;

pub use registry::register_containers;

Modules

container

Still-image JPEG container (.jpg / .jpeg).

decoder

JPEG packet decoder — baseline (SOF0) and progressive (SOF2).

encoder

Baseline / progressive JPEG encoder.

error

Crate-local error type used by oxideav-mjpeg’s standalone (no oxideav-core) public API.

image

Crate-local frame and pixel-format types used by oxideav-mjpeg.

jpeg

Baseline JPEG bitstream primitives.

mjpeg_container

Raw Motion-JPEG container (.mjpeg / .mjpg).

registry

oxideav-core integration layer for oxideav-mjpeg.

rtp

RTP/JPEG depacketization (RFC 2435).

Constants

CODEC_ID_STR