This article sets its focus to the Dolby Vision Content Mapping Unit, widely known as the CMU. We'll cover the following topics:
 

• External Content Mapping Unit – eCMU
• Internal Content Mapping Unit – iCMU
• Comparison between an iCMU and an eCMU

The Dolby Vision Content Mapping Unit (CMU) enables real-time Content Mapping (CM) processing for Dolby Vision mastered content when connected to or implemented in a 3rd party Dolby Vision enabled color grading or mastering product. Dolby Vision Content Mapping also enables HDMI Tunneling that allows users during the content creation process to preview their work in Dolby Vision on a Dolby Vision consumer television.
HDMI Tunneling - Previewing the grade on a Dolby Vision TV

 

External (hardware) Content Mapping Unit – eCMU

**The Dolby eCMU was discontinued in early 2024, and there will be no further updates provided for this product.

 

The eCMU performs the content mapping function using content with embedded Dolby Vision metadata from a supported color correction or mastering system, delivered over an SDI interface. The eCMU can map HDR content to a specified target that can then be viewed on a suitable target display. The applications enabled with Dolby Vision must also communicate with the eCMU via a data network, either connected directly or as part of a larger in-house network. This traffic is minimal and generally only occurs at startup or during project initialization.
See the Dolby Vision External Content Mapping Unit (eCMU) User Manual for a detailed setup guide of an eCMU.

Dual Mastering monitor eCMU setup example

An eCMU can only be purchased from an authorized CMU systems integrator:

Authorized CMU System Integrators:

• USA: New Media Hollywood
• Europe: Armari
• Asia Pacific: Altec and Digitocean

 

Internal (software) Content Mapping Unit – iCMU

Color correction systems and mastering systems that support Dolby Vision content creation, now have an integrated CMU (iCMU) capable of performing real-time Content Mapping (CM) processing within the system. With the rollout of Dolby Vision CMv4.0, most systems now support the iCMU as a standard feature. The video output resolution, bit depth and signal format capabilities of an iCMU are determined by the video I/O capabilities of the respective color grading or mastering tool.
Using an iCMU and appropriate hardware, the user can now see their HDR and mapped versions, simultaneously on two separate displays, running side by side. The color grading or mastering system must have video output hardware capable of supporting two simultaneous streams of video at the required resolution and frame rate.
To determine the capabilities of your video output hardware when using the iCMU dual output feature, please refer to the accompanying documentation as well as the user manual of your Dolby Vision enabled color grading or mastering tool. 
 

Single Mastering monitor iCMU setup example

Dual Mastering monitor iCMU setup example

 

Comparison between an iCMU and an eCMU

	iCMU	eCMU
CMv.2.9	yes	yes
CMv.4.0	yes	yes
HDMI Tunneling	yes*	yes*
Dual output	yes**	yes
Supported frame rates	depending on video board	23.976, 24, 25, 29.976, 30
Supported resolutions	depending on video board	Up to 2x UHD-1 (2160p)
External hardware required	no	yes

* HDMI Tunneling is available to all Dolby Vision 3rd party Dolby Vision enabled color grading or mastering tools for integration. For a comprehensive list of systems and tools supporting HDMI Tunneling please check this link.
HDMI Tunneling 4.0 is supported on eCMU version 5.1.0 and higher.
** Please check your vendor's capabilities for dual output functionality on iCMU.