Chapter 21: Timing Nodes

The Timing node menu provides nodes that change the timing of input sequences, either as their main purpose (the Sequence and 3:2 nodes) or as a secondary effect (Merge and Split).

In This Chapter

Guidelines for Choosing the Right Video Field Node

Sequence Node

Merge Node

Split Node

3:2 Pulldown Node

3:2 Pushup Node

The Sequence node is a comprehensive tool for adjusting image sequences. It duplicates much of the functionality of the Clip Editor to enable you to re-sequence imagery at any point in a network. In addition, the Sequence node enables you to splice frames from different input sequences together.

The 3:2 nodes, on the other hand, are designed specifically to perform telecine (film transfer) type operations, converting image sequences to and from film and video frame rates. Use 3:2 Pulldown to transfer film to video rates. Use 3:2 Pushup to transfer video to film rates.

The Split node separates each frame of the input into a pair of "field frames," one odd, one even, such that the output of the Split node is twice the length of the input sequence. The Merge node takes an input of these field frames and merges the fields back together. This means that the output of the Merge node is half the length of the input.

Note:

Two more video-related nodes, Interlace and Deinterlace, are described in Chapter 20: Conversion Nodes.

Guidelines for Choosing the Right Video Field Node

To extract either the odd or even field of each frame, use the Deinterlace Node in chapter 20. To re-interlace an input consisting of an odd field sequence with a corresponding input consisting of the even field sequence, use the Interlace Node in chapter 20. (For both of these nodes, the output sequence is the same length as the input.) These nodes are located in the Convert node menu.

To create a single sequence of alternating odd and even fields in separate frames, use the Split node. The Merge node is used to reintegrate the output of the Split node.

Image showing how the Interlace and Deinterlace nodes differ from the Merge and Split nodes.

Fig. 21.1 Note the difference between the output of the Deinterlace node and the Split node. The Interlace node is used to reintegrate the output of two Deinterlace nodes, while the Merge node reintegrates the output of a Split node.



Sequence Node

Sequence node icon. The Sequence node is a multi-input node that is used to re-sequence image frames. Unlike the Clip Editor, which is used to re-sequence source imagery when it is created or imported, the Sequence node can be used at any point in a network. It also enables you to combine frames from more than one node into a new sequence.

The Sequence node can be used to

You can connect as many inputs to Sequence as you need. Each time you connect an input, a new connector is created on the Sequence node and a corresponding entry is created in the Sequence Node Panel.

Note:

 

You can connect the same node to Sequence multiple times and a separate entry will be created in the Sequence Node Panel for each input connection. This gives you the option to specify a different range of frames in each entry, and apply different holds and loops to each.

Sequence Parameters

At the top of the Sequence Node Panel is an overall parameter used to specify the starting frame of the output sequence. The other parameters are dynamic; that is, a parameter group is created for each input to the Sequence node.

Start At

This parameter specifies the frame number in global time (in the Time Scooter) at which the output sequence will begin.

Input Entries

Each input entry includes the same set of parameters to specify range, increment, frame repeats, and loops.

The top-level of the input entry has a double-arrow button you can drag up or down to reorder the entry in the list, as the output sequence is ordered from the top entry to the bottom, as explained in Working with Multiple Inputs.

 Image showing Sequence node parameters.

Fig. 21.2 Sequence node parameters.

Range

The Range parameter provides fields in which to enter the first and last frame of the input to use, as well as the increment. The fields are labeled "B" for Begin, "E" for End, and "I" for Increment.

The default range is the range of the input sequence:

The default increment is 1, which specifies that every frame be used. An increment value of 2 would specify every other frame, and so on.

Range Settings

Resulting Sequence

Begin: 1; End: 10; Inc: 1

1 2 3 4 5 6 7 8 9 10

Begin: 10; End: 1; Inc: 2

10 8 6 4 2

Play On

The Play On menu is used to repeat, or hold, every frame specified in the Range parameters. The default is to play on Ones, which uses each frame once. To double frames, select play on Twos; to triple frames, play on Threes; and to quadruple frames, play on Fours.

Play On Settings

Resulting Sequence

Begin: 1; End: 10; Inc: 1
Play on Twos

1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 10

Begin: 10; End: 1; Inc: 2
Play on Threes

10 10 10 8 8 8 6 6 6 4 4 4 2 2 2

Hold First and Hold Last

Use the Hold First and Hold Last parameters when you want to hold (repeat) just the first or last frame of a sequence.

The default value in each parameter field is 0, which indicates that the corresponding frame will not be repeated. To hold, say, the last frame for 1 second at film speed, you would enter 24 as the value in the Hold Last field.

Hold Settings

Resulting Sequence

Begin: 1; End: 10; Inc: 1
Play on Twos
Hold First: 1

1 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 10

Begin: 10; End: 1; Inc: 2
Play on Threes
Hold First: 2; Hold Last: 1

10 10 10 10 10 8 8 8 6 6 6 4 4 4 2 2 2 2

Loop Type

The Loop Type menu is used to add one or more loops; that is, to repeat the entire sequence of frames specified in the input entry. The default is None (no looping); to loop the sequence, select one of the following types of loop from the menu:

Loops

The Loops parameter becomes active when a Cycle or Bounce loop is selected in the Loop Type menu. Enter the number of iterations into the Loops field. The default number of loops is 1 (the minimum).

Loop Settings

Resulting Sequence

Begin: 1; End: 10; Inc: 1
Play on Twos
Hold First: 1
Loops: 1; Cycle Loop

1 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 10 1 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 10

Begin: 10; End: 1; Inc: 2
Play on Threes
Hold First: 2; Hold Last: 1
Loops: 1; Bounce Loop

10 10 10 10 10 8 8 8 6 6 6 4 4 4 2 2 2 2 4 4 4 6 6 6 8 8 8 10 10 10 10 10

Working with Multiple Inputs

The output of the sequence node will be the combined sequence created by all of the input entries, in the order in which they appear in the Node Panel list.

Say that you have input the same node into a Sequence node three times, with the parameters for each entry set as follows (any parameter value not explicitly stated is assumed to be at its default value):

First (Top) Input Entry

Begin: 1; End: 10; Inc: 1

Second Input Entry

Begin: 10; End: 1; Inc: 2

Third Input Entry

Begin: 1; End: 5; Inc: 1; Hold First: 4

With a Start At parameter value of 1, the output to such a sequence node would be frames 1 to 24; with the image data used for each frame consisting of the following input frames in this order:

1 2 3 4 5 6 7 8 9 10, 10 8 6 4 2, 1 1 1 1 1 2 3 4 5.

Tip:

 

Use the Fit Range Button in the Flipbook controls to update the frame range to reflect the changes made in the Sequence parameters.



Merge Node

Merge node icon. The Merge node enables you to recombine video imagery that has been split into a single sequence of alternating odd and even field frames.

The Merge node accepts one input and can be used to recombine frame fields that you split apart using the Split Node.

Diagram illustrating action of Split and Merge nodes.

Fig. 21.3 The Merge node recombines the alternating odd and even field frames output by the Split node.

Merge Parameters

The Merge Node Panel offers menus for selecting field order and input style. Your choices should be based on the method used previously to split the frames in the Split node.

Field Order

This parameter allows you to specify the order in which the field frames were generated in the Split node: "Field Two, Field One" (field two first), or "Field One, Field Two" (field one first).

Input Style

This parameter specifies the input style used when the fields were split:

Thrown Away

This input style is appropriate for fields that were previously split using the "Throw Away" option in the Split node, which has the effect of shrinking the input image by 50 percent in height.

Copied

This input style is appropriate for all fields that were previously split using an option other than "Throw Away." Select this option to merge fields that were previously split using the "Use Black," "Copy from Previous," or "Average Above and Below" options in the Split node.



Split Node

Split node icon. The Split node enables you to separate a series of frames into alternating "field frames." Take, for example, a video clip of one second duration (30 frames). The Split node will split such a video clip into a 60-frame sequence that alternates even and odd fields as separate frames. Therefore, the Split node accepts one input and outputs twice as many frames as in the input sequence. See also Fig. 21.3.

Note:

 

Use the complementary Merge Node to recombine the field frames. To de-interlace frames and keep only the odd or even field information in each frame, without creating additional frames, use the Deinterlace Node in chapter 20 instead of Split.

Split Parameters

The Split Node Panel provides a pair of menus for specifying the field order and how to treat the other field.

Field Order

Use the Field Order menu to specify whether the alternating field frames generated by the Split node should begin with field 1 (the odd field lines: 1, 3, 5, etc.) or field 2 (the even field lines: 2, 4, 6, etc.).

Other Field Fill

Use this menu to specify how to treat the vacant spaces that remain once the odd and even scan lines have been split into separate field frames.

Diagram illustrating effect of various field-fill parameter options in the Split node.

Fig. 21.4 Options available for filling the discarded field.

Use the Other Field Fill menu to select one of the four available options:

Use Black

This option fills the vacant lines with black.

Copy from Previous

This option fills the vacant lines with data replicated from each previous line.

Average Above and Below

This option fills the vacant lines with data obtained by averaging the preceding and subsequent lines together.

Throw Away

This option discards the data that formerly occupied the now-vacant lines. The Throw Away option has the effect of shrinking your file by 50% in the Y dimension. (In other words, a file that was originally 720 x 486 will become 720 x 243.)



3:2 Pulldown Node

3-2 Pulldown node icon. The 3:2 Pulldown node enables you to convert imagery from the frame rate of film (24fps) to the frame rate of video (30fps).

By video, we are actually referring to the 525/60 scan rate associated with NTSC video. The PAL video standard is associated with the 625/50 scan rate, and the transfer from 24fps to 50fps is typically accomplished by a simple doubling. The Sequence Node can be used to double frames by selecting Play On Twos.

Note:

 

To convert video to the frame rate of film, use the complementary 3:2 Pushup Node.

How 3:2 Pulldown Works

A 3:2 pulldown creates five video fields from every two input frames by replicating one field from every other frame. There are two basic pulldown patterns used to pad the frames to 60 fields per second: 3:2 and 2:3.

Diagram showing how film frames are distributed to video fields in a pulldown.

Fig. 21.5 Typical 3:2 pattern: the first film frame is repeated for three video fields and the next film frame for two fields, and so on until the end of the sequence.

Selecting a Phase Shift

There are actually a total of five different permutations, or phase shifts, of the pulldown pattern to choose from when you need to match other existing video footage that has been edited on fields rather than frames.

The choice of phase shift only becomes important if the film sequence to be transferred will be spliced into other video sequences or if the footage will eventually be transferred back to film speed:

Phases A - E

In RAYZ, the phase shifts are labeled A, B, C, D, and E. The letters refer to the type of edit frame on which the 3:2 or 2:3 pattern starts. There are four types of edit frame (which are illustrated in Fig. 21.5):

Phase A starts on the A frame (ABCD), making it a 2:3 pattern.

Phase B starts on the B frame (BCDA), making it a 3:2 pattern.

Phase C , which starts on the C frame (CDAB), is a 2:3 pattern where the first edit frame will used in two separate video frames. This may be necessary to match the sequence to the way another one has been edited, given that video is edited field by field, rather than frame by frame.

Phase D (DABC) is a 3:2 pattern where the first edit frame will used in two separate video frames, for the same reason as Phase C.

Phase E is the same as A, except that it repeats the initial A frame (A+ABCD).

Depending on the system used for a pulldown, the five permutations may be referred to using different terminology, such as by phase numbers (Accom, e.g.) instead of letters, or by the pattern of whole and split video frames used.

Whole and Split Frames

A whole frame uses the same film frame image for both fields, while a split frame uses a different film frame image in each field (see Fig. 21.5). For example, WWSSW indicates a repeating pattern of two whole frames followed by two split frames followed by a whole frame.

The following chart can be used as a guide if you, or those you need to communicate with about the process, are familiar with different terms:

Phase 1

Phase 2

Phase 3

Phase 4

Phase 5

Phase A

Phase B

Phase C

Phase D

Phase E

WWSSW

WSSWW

SSWWW

SWWWS

WWWSS

ABCD

BCDA

CDAB

DABC

A + ABCD

2:3

3:2

2:3
(split first)

3:2
(split first)

2 + 2:3

Pulldown Parameters

The 3:2 Pulldown Node Panel provides parameters for selecting the phase shift and field order to use.

Phase Shift

The Phase Shift menu is used to select the type of conversion the 3:2 Pulldown node should use. Select A, B, C, D, or E to specify a repeating pattern. The most commonly used phase shifts are A (a 2:3 pattern) and B (a 3:2 pattern). See also Selecting a Phase Shift.

Field Order

This menu is used to specify the order in which frames of the input are assigned to the two interlaced fields that make up each video frame of the output. Field 1 has the odd field lines (1, 3, 5, etc.) and field 2 the even field lines (2, 4, 6, etc.).

Field Two, Field One

This is the default menu choice. Field 2 of the video frame is filled before field 1. In the case of a split frame (where two separate film frames are assigned to the same output video frame), the first film frame image is assigned to field 2, and the subsequent film frame is assigned to field 1.

Field One, Field Two

If you select this option, field 1 of the video frame is filled before field 2.

Diagram showing how field order affects which video fields are filled with which frame of film data.

Fig. 21.6 Field order affects which video field is filled with which frame of film data. Phase Shift B was selected in this example.



3:2 Pushup Node

3-2 Pushup node icon. The 3:2 Pushup node enables you to convert imagery from the frame rate of NTSC video (30fps) to the frame rate of film (24fps). It performs an inverse of a 3:2 pulldown by creating two film frames from five video fields by disposing of one of the fields.

Note:

 

Note: For more information about the film transfer process, refer to the description of the 3:2 Pulldown Node.

Pushup Parameters

The 3:2 Pushup Node Panel provides parameters for selecting the phase shift and field order to use.

Note:

 

When using the 3:2 Pushup node to convert video frames that were originally created from film frames using the 3:2 Pulldown node, use the same Phase Shift and Field Order parameter settings that were used in the 3:2 Pulldown node.

Phase Shift

The Phase Shift menu enables you to choose a pattern by which the 3:2 Pushup node will perform the conversion. There are five different phase shifts to choose from, each of which corresponds to a pulldown phase shift as described in the section on Selecting a Phase Shift in the 3:2 Pulldown node description.

Field Order

This menu specifies the order in which the two fields that make up each frame of video are processed: "Field Two, Field One" (field 2 first) or "Field One, Field Two" (field 1 first). Be sure to match the field order that was used in the previous pulldown operation, if any, or that of other video footage with which it may be combined.