Sequence Node

The Sequence node enables the Chalice system to address any sequence of frames for processing. You can use the Sequence node to perform the following tasks:

  • remap frame numbers
  • hold (repeat) frames
  • skip frames
  • specify a list of frames in any order
  • combine frames from multiple input sequences

The Sequence node works by remapping frame numbers according to your specifications. In Chalice, the Exec node is the main processor and sends frame numbers to the nodes connected to the left of it, upstream in the network, when you execute (process) a shot. In most situations, these numbers represent the current output frame.

The Sequence node essentially translates the numbers that are delivered to it on the right to a new set of numbers that it will pass to the left, upstream. Once the numbers are determined, the actual image data that the Sequence node receives from upstream nodes is passed downstream (to the right) without modification by the sequencer.

Note:
You can resequence frames directly in the Disk Input node. The Sequence node is used when you want to re-sequence frames later in the network, or when you need to resequence frames from multiple source nodes.

Sequence Parameter Tab

Chalice creates an entry panel in the Sequence tab for each input node you connect to the Sequence node. This is where you specify which input frames the Sequence node will use and how the frames will be ordered.

See List

The See List button (+) displays a window that shows the numbers delivered to the right of the Sequence node, the input frames selected, and the frames delivered to the left of the Sequence node.

Sequence List Entries

The entry panel for each input to the sequence node features several parameter controls, which are described in the following paragraphs. The next section of this node description, Sequencing Examples , also helps explain how to use this node.

Up Arrow Icon

You can easily change the order of the entries in the Sequence List area. Clicking the Up Arrow icon in a panel moves that entry one step closer to the top of the list.

In, Out, and Incr. Fields

Key in a value for the In parameter to specify the first frame of the input to use.

Key in a value for the Out parameter to specify the last frame of the input to use.

Key in a value for the Incr. parameter to specify the frame increment . For example, an increment value of 1 specifies every frame, and a value of 2 specifies every other frame.

Use File Option

There are two ways to specify how an input can be re-sequenced. You can key values representing frame numbers into the In, Out, and Increment parameters (the default), or you can create an ASCII text file that contains a list of numbers.

To access the text file list, click the Use File button. The parameter will change to display a path field and an associated Choose File button (plus icon), which brings up a dialog box that enables you to select a file. This file should be an ASCII text file that contains a list of numbers delimited by carriage returns. These numbers represent a list of frames and will override the In, Out, and Increment parameter values.

This option is particularly useful for specifying a highly random order of frames. (See also Example 3: Single Sequence, Irregular Ordering of Specific Frames .)

Click the Use File button (file folder icon) again to toggle back to default mode.

Hold Fields

Key in a value for the First Hold parameter to specify the number of times you wish to repeat (hold) the first frame of the entry sequence.

Key in a value for the Last Hold parameter to specify the number of times you wish to repeat (hold) the last frame of the entry sequence.

Key in a value for the Mid Hold parameter to specify the number of times you wish to repeat (hold) the middle frames of the entry sequence. The term "middle" in this case refers to all the frames in the sequence that fall between the first and last frames.

Tip:
One common application of the Hold parameters is to double frames. Simply key the same number of Hold frames into all three Hold parameter fields. To double frames, key in 1 for the value; to triple frames, key in 2; to quadruple frames, key in 3; and so on.

Loops

Key in a value for the Loops parameter to specify the number of iterations of the sequence. If you specify more than one iteration, use the Cycle and Bounce buttons to specify the type of looping (see also Example 2: Repeats and Looping ):

  • Selecting the Cycle button instructs the Sequence node to repeat a sequence in order. For example, a sequence of three frames will repeat as 1, 2, 3, 1, 2, 3, 1, 2, 3, etc.
  • Selecting the Bounce button instructs the Sequence node to repeatedly play forward, then back, through a sequence. For example, a sequence of three frames will repeat as 1, 2, 3, 2, 1, 2, 3, 2,1, etc.

Sequencing Examples

The following examples should help you understand how to use the Sequence node to accomplish specific types of resequencing, as well as exactly what results to expect.

Example 1: Using Two Sequences and Remapping

In this example we will set up two streams of imagery to be sequenced one after the other by connecting two Disk Input nodes to a Sequence node. The Sequence node will then display two sequence entry panels.

We wish to produce a 14-frame sequence, and have set the parameters for the Exec node accordingly. We wish to use frames 700 through 704 from one Disk Input node for the first five frames of the output, and to use frames 21 through 29 from the other Disk Input node for the following 9 frames.

We will assign the following parameters to the first sequence entry:

In = 700 Out = 704 Increment = 1
First Hold = 0 Mid Hold = 0 Last Hold = 0 Loops = 1

We will assign the following parameters to the second sequence entry:

In = 21 Out = 29 Increment = 1
First Hold = 0 Mid Hold = 0 Last Hold = 0 Loops = 1

In this case, as the Exec node sends the numbers 1 through 14 upstream, the Sequence node acts like a switch and a remapper of numbers.

For the first five frames the Sequence node will request frames 700-704 from the Disk Input node connected to the first sequence entry and pass the image data for those frames downstream, renumbered 1 through 5.

As the Exec node requests numbers 6 through 14, the Sequence node will switch to the second sequence entry and request frames 21-29 from the second input node. Then it will pass the image data for those frames downstream, renumbered 6 through 14.

The following chart maps the behavior of the Sequence node. (This information is also generated by the Sequence node when you click the See List button.)

Input Frame Delivered Number Delivered
Accessed on Left on Right
Disk Input node 1 700 1
Disk Input node 1 701 2
Disk Input node 1 702 3
Disk Input node 1 703 4
Disk Input node 1 704 5
Disk Input node 2 21 6
Disk Input node 2 22 7
Disk Input node 2 23 8
Disk Input node 2 24 9
Disk Input node 2 25 10
Disk Input node 2 26 11
Disk Input node 2 27 12
Disk Input node 2 28 13
Disk Input node 2 29 14

Example 2: Repeats and Looping

This example demonstrates two types of looping (repeat) control. In this case we will repeat each sequence entry once by changing the Iteration value to 2. For the first entry we will select the Cycle button to repeat the sequence in a simple loop. For the second entry we will select the Bounce button to repeat the sequence in a ping-pong fashion.

We will assign the following parameters to the first sequence entry:

In = 700 Out = 704 Increment = 1
First Hold = 0 Mid Hold = 0 Last Hold = 0 Loops = 2
Loop control: Cycle

We will assign the following parameters to the second sequence entry:

In = 21 Out = 29 Increment = 1
First Hold = 0 Mid Hold = 0 Last Hold = 0 Loops = 2
Loop control: Bounce

Given these parameter settings, the Sequence node will generate the following result:

Input Frame Delivered Number Delivered
Accessed on Left on Right
Disk Input node 1 700 1
Disk Input node 1 701 2
Disk Input node 1 702 3
Disk Input node 1 703 4
Disk Input node 1 704 5
Disk Input node 1 700 6
Disk Input node 1 701 7
Disk Input node 1 702 8
Disk Input node 1 703 9
Disk Input node 1 704 10
Disk Input node 2 21 11
Disk Input node 2 22 12
Disk Input node 2 23 13
Disk Input node 2 24 14
Disk Input node 2 25 15
Disk Input node 2 26 16
Disk Input node 2 27 17
Disk Input node 2 28 18
Disk Input node 2 29 19
Disk Input node 2 28 20
Disk Input node 2 27 21
Disk Input node 2 26 22
Disk Input node 2 25 23
Disk Input node 2 24 24
Disk Input node 2 23 25
Disk Input node 2 22 26
Disk Input node 2 21 27

Example 3: Single Sequence, Irregular Ordering of Specific Frames

In this example, assume that the Sequence node has one input consisting of a 100-frame sequence and that we wish to select 10 very specific frames for output. We wish to select frame 5 of the input sequence as the first frame, frame 8 as the second frame, and so on as listed below:

5
8
4
9
10
1
6
2
3
7

To accomplish this, we will create an ASCII file of the 10-frame sequence in the exact order we require and access it from the Sequence node.

In the Sequence parameter tab, click on the Range button to indicate that you wish to use a file instead of the In and Out parameters. A Choose File button will appear. Click this button to display the Choose File dialog box and select the ASCII file. The Sequence node will extract the numbers from the file and generate the following result:

Frame Delivered Number Delivered
on Left on Right
5 1
8 2
4 3
9 4
10 5
1 6
6 7
2 8
3 9
7 10

If we were to increase the default value of 1 in the Loops parameter, the Sequence node would repeat the numbers from the ASCII file in either a Cycle or Bounce fashion, depending on which button we selected. As with Loops, whatever values we set in the Hold parameters would also be applied to the frames of the file list.




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