Adobe Creative Cloud

details of video preview with Mercury Transmit in the 2014 update to After Effects CC

NOTE: This article is about new functionality in the 2014 update to After Effects CC, which is one of the many Creative Cloud updates announced today. For more details about this release of After Effects, read the complete list of what’s new and changed.

After Effects has for a long time had the ability to send frames to a video device for preview, for example on a broadcast monitor. In the 2014 update to After Effects CC, the underlying architecture for that functionality has been replaced with the same Mercury Transmit technology used by Premiere Pro.

This is an important change for After Effects because it removes a dependency on fragile, deprecated operating system components. Aside from that, Mercury Transmit allows for new functionality and enhancements with video preview:

  • Full-screen display on a monitor connected to your computer’s video card. This includes the HDMI port built into recent models of MacBook Pro.
  • 10-bit color output in 16-bpc and 32-bpc projects when using devices from AJA, Blackmagic Design, Bluefish444, and Matrox.
  • RAM preview frame rate performance is improved for memory-intensive compositions when video preview is enabled.
  • Simplified controls that no longer require you to specify the output video mode; After Effects and the device negotiate to set the video mode.

In addition to the above changes provided by Mercury Transmit, in the 2014 update to After Effects CC, the video preview image is color managed in the Rec. 709 color space.

Below are details about how video preview works in the 2014 update to After Effects CC, including known issues and limitations. If you have questions about these changes, please post to this thread in the After Effects user-to-user forum.


what is Mercury Transmit?

Mercury Transmit is a software interface that Adobe digital video applications use to send video frames to external video displays. Video device manufacturers AJA, Blackmagic Design, Bluefish444, and Matrox provide plug-ins that route the video frames from Mercury Transmit to their hardware. The same Mercury Transmit plug-ins work in Adobe Premiere Pro, Prelude, Speedgrade, and After Effects.

Mercury Transmit can also use monitors connected to your computer’s video card and FireWire-connected DV devices without an additional plug-in.

IMPORTANT: Mercury Transmit does not use GPU acceleration. It is a different technology from the Mercury Playback Engine in Premiere Pro.


how to set up video preview using Mercury Transmit in After Effects

To enable video preview with Mercury Transmit, open Preferences > Video Preview, choose Enable Mercury Transmit, and choose a video device from the list.

  • Devices named AJA Kona 3G, Blackmagic Playback, or similar represent a video device connected to your computer.
  • Adobe Monitor devices are the computer monitors connected to your video card.
  • Adobe DV requires a DV device connected to a FireWire port on your computer.

To change the options for your video device, click the “Setup” text next to the device name. More options may be available in the device’s control panel or management application.

To toggle external video preview on or off without opening the Preferences dialog box, press the forward slash (/) key on the numeric keypad. On a Mac keyboard without a numeric keypad, such as on a MacBook, use Control+Shift+/.


using color management with video preview

When you choose a color working space for the project, the image sent to the video preview monitor is transformed from the working color space to the Rec. 709 color space. The gamma curve of the image is linearized (gamma = 1.0) if the Linearize Working Space option is enabled.

If you use a monitor with a color profile other than Rec. 709, please tell us more about your workflow in this forum thread.


general notes about using video preview

In the Composition, Footage, and Layer panels:

  • Overlays such as safe margins, guides, mask paths, and effect controls are not sent to the video preview monitor.
  • Viewer settings such as magnification (zoom), color and alpha channel views, transparency grid (checkerboard), pixel aspect ratio correction, and exposure do not affect the video preview image.
  • When the region of interest is enabled, or when mask views are enabled in the Layer panel, the visible image will be scaled up to the size of the composition on the video preview monitor.
  • Fast Draft preview mode does not interactively update the video preview image. The video preview image will update when the mouse button is released.
  • Wireframe preview mode does not update the video preview image. Switch to a different preview mode to update the video preview image.

When rendering a composition using the render queue, After Effects will update the image on the video preview monitor. To disable this, turn off the Video Preview During Render Queue Output option in Preferences > Video Preview.

After Effects will stop sending the video preview image to the video preview monitor if you switch to a different application. To allow After Effects to continue to use the video preview monitor when it is not the frontmost application, turn off the Disable Video Output When In The Background option in Preferences > Video Preview. Note that After Effects will stop updating the image when it is not the frontmost application. RAM previews and render queue output will continue to render, but the image on the video preview monitor will not be updated until you return to After Effects.


performance of RAM preview playback when video preview is enabled

Video preview from After Effects requires additional processing power, which may cause RAM preview playback speeds to be less than real-time for memory-intensive compositions. This was true in previous versions of After Effects and remains true for video preview using Mercury Transmit, although Mercury Transmit provides better performance than the previous technology.

RAM preview frame rate performance is affected by a combination of your computer’s capabilities and the memory requirements of the composition. If you do not get real-time performance during RAM preview, try the following:

  • Reduce the resolution in the Composition or Preview panels.
  • Reduce the RAM preview frame rate in the Preview panel.
  • Reduce the project color depth to 16-bpc or 8-bpc, if applicable.
  • Disable color management (set the project’s working space to None).


notes about using video preview with AJA, Blackmagic Design, Bluefish444, and Matrox devices

Download the latest drivers and Mercury Transmit plug-ins for your device. While After Effects uses the same Mercury Transmit plug-ins as Premiere Pro, the plug-ins need to be updated for compatibility with After Effects.

AJA: The AJA Preview plug-in will conflict with Mercury Transmit for control of the monitor. Either disable Mercury Transmit (Preferences > Video Preview) or disable the AJA Preview plug-in (Window > AJA Preview).

Blackmagic Design: Blackmagic devices will not output compositions that do not match the device’s supported video modes. (ex. 720p59.94) Refer to the documentation for your Blackmagic device for a list of supported video modes.

Bluefish444: Check the Bluefish444 web site for up-to-date documentation.

Matrox: Uninstall previous drivers and install the latest drivers for your Matrox device. The driver installation will detect which versions of After Effects are installed on your computer and install the Mercury Transmit plug-in and/or the Matrox WYSIWYG plug-in that is appropriate for each version.


notes about using video preview with a computer monitor

The monitors connected to your video card appear as Adobe Monitor 1 or 2, etc. in the Video Preview preferences. These monitors will only be available when there is more than one monitor connected and the desktop is extended across these monitors. Desktop mirroring must be disabled.

Video preview using Mercury Transmit does not work on the same monitor that is being used by the After Effects application frame. Move or resize the application frame so it does not stretch across the monitor that you want to use for video preview. Panels can be undocked and placed on that monitor, but they will not be visible when Mercury Transmit is enabled.

The Full Screen option in the Preview panel is not compatible with Mercury Transmit. Disable it when using a monitor connected to your video card.

The video preview image is displayed full-screen on the computer monitor, with letterbox or pillar-box bars as appropriate, regardless of the size of the composition or the resolution of the monitor.

The video preview image may not display correctly if you plug in the monitor cable while After Effects is running. Quit and restart After Effects to get a correct preview.

After Effects, General, Region of Interest