Quicktime Streaming Devices (Pcie Or Usb/Firewire) - PRG MBOX User Manual

Alternative Cropping for Video Inputs
The cropping for video inputs mentioned on the previous page is intended to be used for small amounts of cropping,
to clean up the edges of a video input signal. If there is a need to crop out larger parts of the input, then there is an
alternate method of cropping.
The MediaInfo.plist file (Refer to
on a media file. The media file could be a video input, a movie, or a still image. The key is "activerect" and the value
(a string) entered is the X/Y origin for the top-left corner of the resulting image and then the width and the height of the
result. A value of "0,0,500,650" would indicate that the resulting image starts at the top-left corner of the original image
and extends 500 pixels to the right and 650 pixels down.
The activerect can be entered as percentages of the original media if any non-zero number under 1.0 is entered into the
value string. For example, a value of "0.5, 0.5, 0.5, 0.5" would case the bottom-right quadrant (1/4th of the image) to be
used, no matter the size of the media.
The activerect method of cropping can be used directly on video input media locations (255.241 and so on) if the desire
is to crop out some of the input. If however the desire is to receive an input signal that is several video inputs that have
been combined externally and received as a single input (e.g. four 1080p inputs combined into a 4K signal and received
by a Blackmagic Ultrastudio 4K device) then applying a single crop to the video input media item would not allow all four
quadrants to be used separately.
In such cases, the activerect metadata entry can be used with the .mblk (Mbox Link) media item to get the desired result.
The .mblk media item acts as a built-in alias for movie and still image items in the /Mbox/Media folder. Adding a .mblk
media item allows there to be different properties (e.g. an activerect) for different virtual copies of the same media item.
To create a .mblk alias:
Step 1. Create a plain text file using the TextEdit application. This file does not need to have any contents.
Step 2. Save the file with the desired name, but change the file extension from the default (.txt) to .mblk.
Step 3. Put the file into a numbered folder in the /Mbox/Media folder. Give the file an 8-bit numerical prefix, like all
media content files have. This will be the file number used to recall the .mblk item.
Step 4. Add a numerical Folder.File suffix to the file that designates the original media item that the .mblk item is an
alias of. i.e. Index#.Name.Folder#.File#.mblk
Step 5. The final result would look like: "001.MyAlias.255.241.mblk - this is an alias to the first video input.
For example: In the previous situation where a single 4K input represented four individual 1080p video inputs, four .mblk
items could be created, all pointing to the same original media item. Each .mblk item would be given an entry in the
MediaInfo.plist file, with each entry having an activerect key and a corresponding value describing one quarter of the
original input.

QuickTime Streaming Devices (PCIe or USB/FireWire)

Mbox also supports all other capture devices that conform to the QuickTime streaming format. Such devices include
USB and FireWire cameras, and some PCIe capture cards. The configuration for these devices is the same as for
Blackmagic and Active Silicon PCIe devices, except:
+ The input type must be set to "QuickTime" rather than Blackmagic or Phoenix.
+ The input will be selected by name (e.g. "iSight Camera") rather than by number.
+ No configuration of the input format is required as this is set automatically when the QuickTime device is selected.
"MediaInfo.plist" on page 41) has a metadata entry that causes a crop to be made
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