Understanding Standards: TLX

Standards drive many technologies that we use in our day-to-day lives, from media, to medicine, to food production—yet, the average person is not aware of the invisible role that they play. As a Standards Developing Organization (SDO) with over a century of accomplishments, SMPTE and its members strive to create a more interoperable world. In this series, we explore SMPTE Standards in a way that’s easy to understand. Today’s Standard: SMPTE ST 2120, aka TLX.

Commonly considered the successor to SMPTE Time Code, this standard introduces the extensible time label (TLX), describes its characteristics, and specifies its architecture. This new, multipart SMPTE Document Suite collectively describes a system for defining labels for elements of media content, representing the labels in various forms, associating the labels with specific elements of the content, specifying profiles of the labels for particular purposes, conveying individual or grouped labels over various connection means, and storing individual or grouped labels in various formats.

Essentially, Time Code, while versatile on its own, is constrained by the technical limitations of the time it was created. TLX seeks to define a new labeling system, more suited to the needs and technologies of today, that may be used alongside ST 12, and that could eventually replace it. The labeling architecture of TLX could even eventually move beyond time-related labeling.

TLX is very new; the only published standard in the suite so far is SMPTE ST 2120-1:2026-03 Extensible Time Label — Structure. It describes the architecture and data model of extensible time labels (TLX), the relationship to content, one specific representation in the JSON format, and general considerations for the design of applications of TLX Labels. SMPTE ST 2120-2 Extensible Time Label — Items and SMPTE ST 2120-3 Extensible Time Label — Profiles have finished their PCD review period and have moved into the next phase of the Standards process.

For more information about SMPTE, our standards, education initiatives, and events, please visit smpte.org and connect with us! Stay tuned for more simple explanations of SMPTE Standards that make everyone’s lives better!