Preview compositions on external displays with Mercury Transmit by sending real‑time video and audio to supported hardware for accurate monitoring and smoother previews.
Mercury Transmit is a software interface used by Adobe applications to send video frames to external video devices. Hardware manufacturers such as AJA, Blackmagic Design, Bluefish444, and Matrox provide plug‑ins that route frames from Mercury Transmit to their devices.
Video preview using Mercury Transmit sends the contents of the Composition, Layer, or Footage panel viewer to an external monitor. The external monitor can be one of the following:
- A video monitor connected through third-party video hardware such as AJA, Blackmagic, or Matrox I/O devices
- A DV device connected over FireWire
- A computer monitor connected to your video display card via such as HDMI, DVI, VGA, or DisplayPort
The setting of the Resolution menu in the Composition panel determines the resolution for the external video preview.
Mercury Transmit does not send overlays such as user interface controls, guides, warning banners and other items drawn by OpenGL to the external monitor. This also means that Fast Draft and Wireframe preview modes do not send image data to the external monitor.
Video preview preferences
You can set the following video preview preferences by choosing After Effects > Settings > Video:
- Enable Mercury Transmit: Toggle video preview with Mercury Transmit. Use '/' on the numeric keypad to toggle this option. On a Mac computer without a numeric keypad, use Control+Shift+/ on the main keyboard.
- Video Device: Check the box next to any option that appears here to enable video output to the specified device.
- Adobe DV: Select this option for DV devices connected via FireWire.
- Adobe Monitor x: View the list of the attached computer monitors that can receive video preview data through the graphics card.
- Third-party video hardware: View the list of third-party hardware that you have connected. Click Setup to view the options available for each hardware.
- Adobe DV: Select this option for DV devices connected via FireWire.
- Disable video output when in the background: Select this option to prevent sending video frames to the external monitor when After Effects is not the foreground application.
- Video preview during render queue output: Select this option to send video frames to the external monitor when After Effects is rendering frames in the render queue.
If you are previewing an image that does not exactly match the preview monitor's pixel dimensions, the third-party I/O device scales the image. The manner of scaling differs between devices and is in some cases controllable through the Setup options for the device. The setting of the Resolution menu in the Composition panel determines the resolution for the external video preview.
If you experience slow RAM preview frame rates when Mercury Transmit is enabled, try one or more of the following:
- Reduce the resolution in the Composition or Preview panel
- Reduce the RAM preview frame rate in the Preview panel
- Reduce the project color depth to 16-bpc or 8-bpc
- Disable color management by setting the project’s working space to None.
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