How Many Videos Can You Play at the Same Time?

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[SEE ALSO: Optimizing for Speed]

We are often asked if Isadora can separate video images to multiple projectors. The answer is yes: Isadora has the capability to output to as many as six video projectors simultaneously. But you will need to have the right hardware to accomplish this.

The hardware solutions you’ll need to acquire depend on whether you are running Isadora on a laptop or a desktop machine.

ADVICE FOR LAPTOPS

Most laptops do not have more than external video output. But you can connect as many as three video projectors using a device called the Matrox TripleHead2Go.

This device makes your computer think it is connected to a monitor that is 3072 pixels across and 768 pixels down. It then takes this triple-wide image and splits it into three separate video projector outputs. Isadora has a special option in the Video tab of the Preferences to make it easy to take advantage of the TripleHead2Go — you can read more about that in the Isadora manual. (The PDF manual can be found in the “Help” menu of Isadora.)

One piece of advice: make sure to check Matrox’s compatibility page to ensure you purchase the right model for your machine!

ADVICE FOR DESKTOPS

If you’re working on a desktop, then the solution is to add more video cards to your system. These days, it is quite common for each card to have two projector outputs. So, if you need to connect two projectors, then you would add one “dual-head” card.

When calculating the total number of outputs, don’t forget that you’ll probably want one output to display the Isadora user interface. So if you want to connect four projectors, you really want five outputs: one for the “main monitor” and four more for the projectors.

Choosing a card can be daunting, as there are so many possibilities. In our experience, you don’t need to purchase the most expensive, top-of-the-line gaming graphics card to get good performance in Isadora. You can purchase something a bit more modest and still get good performance.

GENERAL ADVICE REGARDING PERFORMANCE

Isadora has the potential to output to as many as six video projectors at a time. But how many you will actually be able to use simultaneously depends on many factors, each of these can have a profound influence on how many clips you can play.

The most important is the resolution of the clips themselves. For instance, you should be able to play four channels of 720×480 DV video easily on a recent Mac Book Pro. But, it is unlikely that even a powerful desktop machine will be able to play four streams of HD 1920×1080. The bandwidth for such a task is enormous — even Isadora’s higher priced competitors cannot achieve this.

The codec you choose to compress the clips is also very important. Many users assume that they should use H264, but often this is the worst choice as it requires a lot of CPU power to decode those files. We suggest the DV-NTSC/PAL codec for standard definition images, and Apple Pro Res for HD images. (For the latter, you really should have an SSD drive to make it work well.) You may also want to try Photo JPEG compressed at 50% or 75% — this is the “lightest” in terms of the burden on the CPU; you will need to see if you are fine with the visual quality.

The most important hardware improvement you can make is the hard drive used to store your clips. Many Isadora users now install SSD (solid-state) hard drives because they are much faster than conventional drives. Some even use a pair of SSDs in a RAID 0 configuration to double the bandwidth — which is about as fast as you can get.

Also, you must consider how you will output those streams. If you want four outputs, you’ll need two dual-head graphics cards and a desktop machine. (Don’t forget that you’ll need a third card to give you an extra monitor on which you can see your Isadora patch, etc.)

If you only need three outputs, then we suggest purchasing a Matrox Triple-Head-2-Go. The TH2Go gives you three outputs per video card output. (It “tricks” the card into thinking it has a triple wide output, and then splits it into three physical outputs that can be connected to three video projectors.) Isadora has helpful setup options in the Stage tab of the Isadora Preferences to make this easy to use.

Finally, to deal with multiple outputs, some users purchase several less expensive computers (i.e., mini Mac) and then add logic to their patches that allows them to synchronize the videos among the computers. (Often this is as simple as sending a “start” command from the master to the slaves over a network.) This is not, however, a built in feature of Isadora. It takes a bit of programming work (and skill) to make this happen. Also, you must consider that you will need an Isadora license for each machine.

In the end, the simplest answer is to give your proposed situation a try. Even users who have not purchased Isadora can easily do this with the demonstration version – you just won’t be able to save your patch. If you wish to play “X” channels of video, then try the following:

  1. Connect the video projectors to your computer. If you need help, refer to the chapter Outputting to a Video Projector in the Isadora manual.
  2. In the Isadora manual, find the section labeled Stage Preferences to learn how to associated Isadora’s “stages” to each of your video projectors.
  3. Add one Movie Player actor and one Projector actor for each video projector connected to your computer. Connect the ‘video’ output of each Movie Player to the ‘video’ input of its matching Projector actor. Then set the ‘stage’ input for each Projector actor to send the image to the desired video projector.
  4. Mac OS X Users: For the very best performance, you should also try the CI Movie Player and CI Projector. They leverage Apple Computer’s Core Image technology, to give you the best performance possible. (These actors are part of the Core Video Upgrade which is $25 extra. If you own Isadora but do not have this upgrade, these actors won’t be available; but they can be used in the demo version.)

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