What Commands Can Be Sent Using HDMI CEC?
Consumer Electronics Control (CEC) is a feature of the HDMI standard that allows interconnected home theater devices to communicate over a single bidirectional bus. By sending standardized electrical control messages, devices like televisions, soundbars, streaming players, and gaming consoles can control one another without requiring direct line-of-sight infrared commands. This article explores the core operational features, functional command categories, and real-world implementation of the HDMI CEC command set.
Core Operational Features
The HDMI CEC protocol specifies a wide range of user-level features designed to simplify media playback and eliminate remote control clutter.
- One Touch Play: Pressing play or a navigation button on a source device (such as an Apple TV, Roku, or Blu-ray player) sends a command signaling the TV and AV receiver to power on, wake from standby, and switch directly to that device's active HDMI port.
- System Standby: Switching off the television or master device broadcasts a standby command across the CEC network, putting all connected, compatible equipment into low-power sleep mode simultaneously.
- System Audio Control: Allows an external audio system, such as an AV receiver or soundbar, to act as the primary volume processor. The TV remote’s volume up, volume down, and mute buttons send signals to adjust the soundbar directly.
- Device Menu Control: Enables the display remote to navigate the on-screen user interface of a connected player using directional arrows, select/enter, return, and menu keys.
- Deck Control: Transmits standard playback transport commands, including play, pause, stop, fast-forward, rewind, skip forward, and skip back.
- One Touch Record: Lets users initiate an immediate recording sequence on an external recording unit or DVR for content currently displayed on the television tuner.
- Timer Programming: Allows a TV or electronic program guide (EPG) device to configure recording timers and scheduling parameters on a connected recorder.
- Tuner Control: Permits an auxiliary controller to switch TV channels, retrieve tuner status, and select digital broadcast frequencies.
Message Structure and Command Categories
HDMI CEC operates over Pin 13 of a standard HDMI cable at a low data rate of approximately 400 bits per second. Each command is constructed with a header block (containing source and destination addresses) followed by an opcode and optional operand data blocks. The HDMI specification divides these opcodes into distinct functional groups:
| Command Group | Representative Opcodes | Functional Purpose |
|---|---|---|
| Power Control | <Standby>,
<Set Path Stream> |
Manages power states and initiates device sleep or wake sequences. |
| Routing & Source | <Active Source>,
<Request Active Source>,
<Routing Change> |
Informs downstream devices which HDMI port should be prioritized on-screen. |
| Transport & Deck | <Play>, <Deck Control>,
<Deck Status> |
Controls playback media engines and queries playback state. |
| Audio Processing | <User Control Pressed> (Volume),
<Set Audio Mode System>,
<Report Audio Status> |
Coordinates volume level syncing and audio format handshakes. |
| OSD & Display | <Set Name OSD>,
<Set OSD String> |
Transmits device identity strings to display accurate labels in the TV source list. |
| Device Discovery | <Give Address Physical>,
<Report Address Physical>,
<Polling Message> |
Maps device topology and detects hot-plug connection events. |
Compatibility and Manufacturer Variations
While HDMI CEC is governed by the HDMI Licensing Administrator, individual hardware manufacturers frequently implement proprietary subsets of the command library. Brands often label CEC under marketing trade names such as Sony Bravia Sync, Samsung Anynet+, LG SimpLink, Philips EasyLink, and Panasonic VIERA Link.
Because manufacturers are not required to implement every opcode
defined in the standard, basic commands like
<Active Source> and <Standby>
enjoy universal support, whereas advanced features like complex menu
navigation or multi-device recording timers may exhibit limited
interoperability across mixed-brand systems.