Tutorial 22: Working With Video Output Components
This tutorial demonstrates how to use Jitter in conjunction with a QuickTime-compatible video output device—such as a DV camera—to send matrices and video sequences directly to hardware, bypassing your computer’s analog video output. We’ll explore the jit.qt.videoout object, and return to the jit.movie object to explore its video output capabilities.
The patch examples in this tutorial assume that you have a DV camera attached to your computer’s FireWire port, powered on and in VTR mode. However, the techniques described will work with any device that has a QuickTime video output component.
End of the Line
You can place the jit.qt.videoout as the final object in a Jitter patch and send processed Jitter matrices directly to a video output device. You'll find that this process is very similar in operation to the jit.grab object that we used in the previous tutorial.
The jit.grab and jit.qt.videoout objects both require that you create a component connection before they can do their work. In the case of the jit.qt.videoout object, that means a connection to a video output device. And, as in the previous tutorial, we'll need to specify the settings we want to use by creating a listing of all our available devices and output modes and choose the settings we want before we use the jit.qt.videoout object. Since we're already familiar with that procedure from working with the jit.grab object in the last tutorial, using the jit.qt.videoout object will be easy.
• Click the
read dozer.mov message box to read an example movie.
Take a moment and look at the patch. By now, you should be familiar with the processes we're using to transform the movie: we separate out a single plane of a matrix using the jit.unpack object, and sent it to the jit.op object. You'll notice that the jit.op and the jit.rota objects are using named matrices to communicate between the jit.rota object’s output matrix and the jit.op object’s right input matrix without using any patch cords. Yep—it's the cool Jitter feedback loop in action.
• Turn on the
toggle attached to the
metro object to start the patch. You’ll notice that
jit.qt.videoout appears to have no effect. Until we send it an
open message, the object simply passes any matrix received via its inlet directly to its outlet. Don’t click the
open message box just yet—we still have some setup work to do.
• Click the
message box that says
getvoclist. Sending a
getvoclist message to the
jit.qt.videoout object causes it to send out its right outlet a list of messages preceded by the symbol
voclist. The items in this list refer to each available
video
output
component —
voc, for short. This list of available video outputs is routed through an
iter object and from there into the
umenu object on the left, from which we can easily make our selection. On our system, the list contains a single item:
FireWire.
If the video output component is registered with the MacOS, it will appear in the
voclist and can be opened
even if the hardware isn't available. If there is no hardware available, the
jit.qt.videoout object will report a
–200 error in the Max Console when you send matrices to it.
• Select the
FireWire output component from the
umenu. This causes the item’s index number (which is the same as its position in the
umenu) to be sent to the
jit.qt.videoout object, via the
voc $1 message. If you don't select anything, the first item in the list will be used as the default component. This is equivalent to sending the message
voc 0 to the
jit.qt.videoout object.
• Click on the
message box that says
getvocmodes to retrieve a list of available modes for the output component you chose. The resulting list, preceded by the symbol
vocmodes, is routed through
iter and into the righthand
umenu object. Our list contains two items:
Apple FireWire NTSC and
Apple FireWire PAL.
• Select the output mode you’d like to use from the
umenu. Your selection will depend on your FireWire hardware—our camera is NTSC, so we’re using
Apple FireWire NTSC mode. This causes the item’s index number (which is the same as its position in the
umenu), to be sent to the
jit.qt.videoout object, via the
vocmode $1 message. If you don't select anything, the first item in the list will be used as the default mode. This is equivalent to sending the message
vocmode 0 to the
jit.qt.videoout object.
• Now we’re ready to start sending data to our output device. Click the
open message box to start the component connection. After a few moments, you should see the same image on your device’s display as you see in the
jit.pwindow in the patch.
If you are getting errors in the Max Console, and not seeing any video on your hardware device, check to make sure that your device hasn’t gone to sleep.
• We have control over other aspects of the output, too. While the specific codec we use is hardware-specific (Apple FireWire always uses the Apple DV codec for output, for example), we do have control over the codec quality of our output. Try selecting different values in the
umenu object connected to the
codecquality $1 message and compare the results on your output device. You should be able to improve speed at the expense of a small loss in image quality by using the Minimum Quality (
codecquality 0) or Low Quality (
codecquality 1) settings. The default is Normal Quality (
codecquality 2).
Summary
The jit.qt.videoout object provides a way to send processed Jitter data directly to a device supported by QuickTime video output components—such as a DV camera—over FireWire.
| Name |
Description |
|
jit.op
|
Apply binary or unary operators
|
|
jit.pwindow
|
Display Jitter data and images
|
|
jit.grab
|
Digitize video from an external source
|
|
jit.movie
|
Play a QuickTime movie
|
|
jit.qt.videoout
|
Output video to QuickTime video output component
|
|
jit.rota
|
Scale/rotate in 2D
|
|
jit.unpack
|
Make multiple single plane matrices out of a multiplane matrix
|
jit.qt.videoout in action