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Digital Cinema Mastering

A cinema master has several distinct properties: the color encoding, the precision of its image values, the file format that stores them, and the compression used for exchange or exhibition. Those properties are related, but a file's bit depth alone does not establish its delivery format. This section explains the conventional SDR DCDM picture path. See Digital Cinema Packages for package authoring, delivery, and exhibition, and HDR Mastering for HDR display targets.

XYZ and Encoded X′Y′Z′

XYZ describes linear CIE tristimulus values. X′Y′Z′ identifies the nonlinear encoded values used for conventional digital-cinema picture. The prime marks matter: a linear XYZ image and a cinema-encoded X′Y′Z′ image require different display processing. The cinema encoding applies a 1/2.6 power function with a defined scale and rounds the result to 12-bit code values.1

Software menus and delivery sheets often shorten the label to “XYZ.” In a DCP or DCDM picture specification, write DCI X′Y′Z′ when referring to the encoded image. Retain XYZ when discussing the underlying linear values, matrices, or chromaticities. This notation does not replace a complete encoding specification, and it does not imply that every HDR cinema format uses the same transfer function.

12-Bit Image Values in a 16-Bit TIFF

A 16-bit-per-channel TIFF really stores 16 bits per channel. A grading system can write image values using that precision. The conventional DCDM interchange mapping separately places 12-bit cinema code values in the most significant 12 bits of each unsigned 16-bit sample. The recommended value for the remaining four bits is binary 0111, or decimal 7.2

Representation Image-value precision Storage or mapping
Conventional DCDM image values 12 bits per X′, Y′, and Z′ component Integer code values from 0 to 4095
Constrained TIFF DCDM The defined 12-bit values in 16-bit samples Upper 12 bits carry the code value; lower four bits are recommended to be 0111
A grading system's other 16-bit X′Y′Z′ TIFF export May contain useful values across all 16 bits Do not assume the low four bits follow the constrained interchange mapping

With the recommended padding, a 12-bit value is stored as TIFF sample = 16 × code value + 7. The lower four bits are padding in that mapping, not four additional bits of image precision. However, TIFF itself does not require every 16-bit image to use that mapping. A filename, an “XYZ” menu label, or a 16-bit export setting does not prove how the image was quantized.

Agree on precision before converting the master

The DI and digital-cinema mastering vendor confirm the required encoding, TIFF mapping, and rounding behavior before rendering. If a 16-bit master carries additional precision that production wants to preserve, retain it rather than treating a 12-bit derivative as its bit-for-bit replacement.

What a Packed DCDM Preserves

A packed DCDM (pDCDM) stores 12-bit DCDM image values in mathematically lossless JPEG 2000 codestreams. Its purpose is smaller, faster interchange between facilities without changing those values. The high-throughput JPEG 2000 block coder is supported for faster processing.3

The defined TIFF-to-packed conversion takes only the upper 12 bits of each 16-bit TIFF sample. Decoding restores those 12-bit values exactly. Converting back to constrained TIFF restores the specified padding, not arbitrary detail previously stored in the lower four bits. “Lossless” here therefore means lossless reconstruction of the 12-bit DCDM image, not preservation of every bit in any 16-bit TIFF supplied to the encoder.4

Packed frames use the suffix .pdc.j2c. They are not substitutes for the lossy JPEG 2000 picture codestreams packaged in a DCP for cinema playback. The mastering facility still authors and checks the exhibition package. See the DCDM workflow and production example for the practical reason to exchange packed masters.

  1. SMPTE, ST 428-1:2019: D-Cinema Distribution Master: Image Characteristics, §§4.2–4.3 and footnote 3, pp. 4–5. ↩

  2. SMPTE, RP 428-5:2010: D-Cinema Distribution Master: Mapping of Images into Constrained Tag Image File Format, §§4.1–4.3, p. 4. ↩

  3. SMPTE, ST 428-24:2024: D-Cinema Distribution Master: Packed Image, introduction and §§5–6, pp. 2, 4–5. ↩

  4. SMPTE, ST 428-24:2024, §8, p. 6. ↩