Overview of JPEG 1

The JPEG 1 standard (ISO/IEC 10918) was created in 1992 (latest version, 1994) as the result of a process that started in 1986. Though, this standard is generally considered as a single specification, in reality it is composed of four separate parts and an amalgam of coding modes.

Part 1 of JPEG 1 (ISO/IEC 10918-1 | ITU-T Recommendation T.81) specifies the core coding technology and it incorporates many options for encoding photographic images. Part 2 defines the compliance testing. Part 3 defines a set of extensions to the coding technologies of Part 1, and via an amendment the SPIFF file format was introduced. Part 4 focuses on the registration of JPEG 1 profiles, SPIFF profiles, SPIFF tags, SPIFF color spaces, SPIFF compression types, and defines the Registration Authorities. And lastly, Part 5 specifies the JPEG File Interchange Format (JFIF). Without any doubt, it can be stated that JPEG 1 has been one of the most successful multimedia standards defined so far.

While JPEG 1 (Rec. ITU T.81 | ISO/IEC 10918) is still the most dominant still image format around, it may seem surprising that ISO/IEC never provided a reference software demonstrating a proper implementation of the standard. Therefore, JPEG initiated an initiative to create a new reference implementation for ISO/IEC 10918. More information on the call can be found here.

JPEG 1 currently includes the following parts:

Part 1: Requirements and guidelines

Specifies the core coding system, consisting of the well-known Huffman-coded DCT based lossy image format, but also including the arithmetic coding option, lossless coding and hierarchical coding.

Part 2: Compliance testing

Specifies conformance testing, and as such provides test procedures and test data to test JPEG 1 encoders and decoders for conformance.

Part 3: Extensions

Specifies various extensions of the JPEG 1 format, such as spatially variable quantization, tiling, selective refinement and the SPIFF file format.

Part 4: Registration authorities

Registers known application markers, SPIFF tags profiles, compression types and registration authorities.

Part 5: File Interchange Format

Specifies the JPEG File Interchange Format (JFIF) which includes the chroma upsampling and YCbCr to RGB transformation.

Part 6: Application to printing systems

Specifies markers that refine the colour space interpretation of JPEG 1 codestreams, such as to enable the embedding of ICC profiles and to allow the encoding in the CMYK colour model.

Part 7: Reference Software

Provides JPEG 1 Reference Software implementations.