Disk Input Node

The Disk Input node enables you to load an image sequence from your hard disk or from a remote directory on a shared volume. Unlike most other Chalice nodes, you cannot feed data from another node into the Disk Input node. Rather, it is common to begin a Chalice network with a Disk Input node.

Importing Image Files

You specify the imagery to import in the Input parameter tab of the Disk Input node by using either of the following methods:

  • Type the complete pathname of the file to be imported directly in the Full Path field.
  • Click the plus button to display a Choose File dialog box.

Using the File Chooser

The Choose File dialog box is a standard Chalice file dialog. You can key the name of the directory you wish to access into the Directory field or click the Directories entries to navigate through the various levels of your file system. For more information on using the navigational features of this dialog, see Opening an Existing File in chapter 5, "Building Chalice Networks ."

The File Chooser dialog features buttons that facilitate locating and importing image files:

  • Click the File Preview button to bring up a monitor display of the currently selected image file in the Files list. File Preview is used to display single image files, so sequence filtering (see below) must be turned off to select an individual file for previewing.
  • Turn on Suffix Filtering to display only those files in the Files list that have legitimate image-file format extensions. Refer to the beginning of this chapter for a complete list of Image File Formats Supported by Chalice .
  • Turn on Sequence Filtering to display one entry per sequence in the Files list. Take, for example, a three-second Cineon shot where each frame is a separate image file named as follows: "filename.0001.cin"; "filename.0002.cin" ... and so on, through ... "filename.0072.cin." With sequence filtering on, the Files list will contain this single entry for the 72 image files: "filename.$F4.cin (1-72)." Turn sequence filtering off (the Sequence Filter button is a toggle) to display all of the files individually.

Note:
You will frequently encounter the "$F" variable , as in "filename.$F4.cin," e.g. The "$F" indicates that the file references a sequence of images, and the "4" indicates that each frame file includes a four-digit frame number padded with zeros, as in "filename.0001.cin." The ".cin" is the file format extension identifying the frames as Cineon-type files.

Once you locate the file you wish to import, click on its name in the file list to select it and then click the Accept button. (Alternatively, you can double-click on its name in the file list.) The Choose File dialog will close and the selected images will be loaded into Chalice.

The Disk Input node panel will appear. The node panel will contain information specific to the imagery that has been loaded. If you click the Frame Icon on the Disk Input node in the workspace, Chalice will display a thumbnail image (an iconic representation of the image) in the Frame Icon.

Parameter Tabs on the Disk Input Node Panel

The Disk Input node features a number of special-purpose parameter tabs (like all Chalice node panels, it also includes an Info Tab , which is described in chapter 6, "Node Panels and Parameters "):

  • The first four tabs are used to specify files to import ( Input tab ), to work with proxy files ( Proxy tab ), to resequence frames ( Sequence tab ), and to add, delete, or swap channels ( Swap tab ).
  • The rest of the tabs on the Disk Input node panel enable you to set options for specific file formats: DPX, Fido, Maya, YUV, and ZPIC . The parameters for these tabs are only available when the source frames are of the corresponding file format.

Input Parameter Tab

The Input tab is used to specify the full resolution image sequence to be imported.

Full Path

The plus button associated with the Full Path parameter opens a Choose File dialog box that enables you to specify the directory location and files you wish to load. Alternatively, you can enter the complete pathname into the Full Path data entry field.

Format

The Format button displays a popup menu of file formats that can be imported by Chalice. The default choice is "Automatic," which indicates that Chalice will examine the image files to determine their format. When it cannot determine the file type, an error message will appear in the Status field of the node panel. In such a case, use the Format menu to tell Chalice the file type of the image you are attempting to import.

Vertical Flip

Certain file formats invert the orientation of images. Click the Vertical Flip checkbox to invert the imagery. (This box can be checked or unchecked at any time to change the orientation of the image.)

Rescan Disk

When you press the Rescan Disk button, Chalice will rescan the source disk to verify that the image file data specified in the Path parameter is up-to-date. If not, Chalice will update the parameter.

Note:
Chalice will perform a rescan automatically whenever the pathname in a Disk Input node is altered, or if a global used in the pathname ($JOB, e.g.) is redefined.

File Info

The File Info parameter enables you to view a list of every frame in the sequence. For each frame it displays filename, width in pixels, height in pixels, number of channels, bit-depth, file size in Megabytes, and file format. If there are gaps in the sequence, this view will identify the missing frames.

Proxy Parameter Tab

The Proxy tab is only used when you want to specify lower resolution files to use in place of the full resolution imagery. You can specify Medium proxies, Low proxies, or both. If necessary, you can create proxy files directly from the Proxy tab, as described below under "Medium Path."

The parameters on the Proxy tab are described below. For a comprehensive overview of the subject, however, see Using Proxies in Chalice at the beginning of this chapter.

Enable Proxy Files

This checkbox is the master control for enabling the use of proxies in a Disk Input node. When you check the box to enable the use of proxy files, the rest of the parameters on the Proxy tab become available. These parameters enable you to specify information about the full resolution files, if they are unavailable, and to specify or create medium and low resolution proxies.

Full Resolution

You always start by pointing the Disk Input node to the full resolution files using the Full Path parameter on the Input tab. Relevant information about the Full Path image sequence is displayed here in a status bar.

If, however, the full resolution imagery is unavailable, you can change the Full Resolution menu choice from the default, "Use Source File," to "Specify Size." This will activate the associated Resolution and Bit Depth parameters, which enable you to specify this information for the full resolution files that will eventually be used for the final shot.

Medium Path

The Medium Path parameters enable you specify the files to be used as medium resolution proxies. These parameters work exactly like those located on the Input tab (refer to the Input Parameter Tab description), including file path, flipping the input, rescanning the disk to update the image file information, and displaying the file info. In addition, however, Medium path includes a "Create Files" option:

Create Files

In some cases, proxy files will already exist on disk or other storage device. In other cases, however, you have to create the proxy files yourself. The Create Files option enables you to create proxy versions of the full resolution imagery directly from this tab. (It is not necessary to connect the input to a Disk Output node and an Exec node to render them.)

When you press the Create Files button, Chalice displays a file creation dialog in which you specify the proxy pathname, resolution, and format, as well as the range of frames to create.

Low Path

The Low Path parameters enable you specify image files to be used as low resolution proxies. The procedure for specifying or creating low resolution proxies is exactly the same as that for Medium proxies, as described directly above.

Sequence Parameter Tab

The Sequence tab of the Disk Input node has essentially the same functionality as the Sequence node, and you can always modify a sequence at any point in a grail network by using the Sequence node. However, this tab enables you to resequence frames immediately upon input, without resorting to another node.

In the Sequence tab, you can

  • specify the range of frames in the selected sequence to import.
  • control the direction in which the frames are accessed.
  • hold frames and add loops.
  • renumber frames as output from the Disk Input node.

The Sequence tab parameters are disabled by default. If you enable the tab by checking the Resequence Source Frames box, all the settings you specify in this tab become applicable until or unless the tab is disabled.

Note:
The Source Frame Range display (top of tab) always reflects the frames as accessed on disk. The Output Frame Range (bottom of tab) display updates to indicate any change in the range as a result of modifying the Sequence parameters.

Resequence Source Frames

This parameter is the master control that enables resequencing. Unless it is checked, none of the other Sequence tab parameters will be available for modification and any previous modifications will be ignored.

Update Parameters if Input Changes

By default, if the input sequence changes the Sequence tab parameters will update to reflect any changes in the sequencing of the source imagery. In some cases, however, you might not want Chalice to make this adjustment automatically. If so, simply uncheck this parameter and the Sequence tab will keep your settings intact.

Frame Range

The Frame Range parameters enable you to specify new starting and ending frames to access and to skip frames by changing the Increment value.

Tip:
When you load a sequence into the Disk Input node, the Source Frame Range display at the top of the tab indicates whether or not the sequence has gaps. If there are gaps, click the "File Info" button on the Input tab to get detailed information about each frame in the source sequence.

Next Frame

This popup menu enables you to change the order in which frames are accessed from "Move Forward," which is the default, to "Move Backward," if you want to reverse the order in which the specified source frames are accessed and, therefore, output from the Disk Input node to the rest of the network.

You can also instruct Chalice to "Pick Random Frames." The randomize option is commonly used for source frames consisting of noise or grain patterns. When Pick Random Frames is selected, the following parameters become available:

  • Random Length enables you to enter the total length in frames that the sequence should be.
  • Random Seed enables you to enter a seed value for the randomize operation.

Holds

First Frame will repeat the first frame in the specified sequence by the value entered in the field; Mid Frames will repeat every frame between the first and last frames by the value entered; and Last Frame will repeat the last frame. To double every frame, for example, you would enter a hold value of 1 in all three Hold fields.

No. of Loops

This parameter enables you to specify the number of iterations of the sequence. If you specify more than one iteration, specify how the sequence should be repeated using the Looping Type parameter (see next).

Looping Type

Cycle will repeat the sequence in order. For example, a sequence of three frames will repeat as 1, 2, 3; 1, 2, 3; 1, 2, 3; etc.

Bounce will repeat the sequence first forward, then backward. For example, a sequence of three frames will repeat as 1, 2, 3, 2, 1, 2, 3, 2,1, etc.

Offset Frame Numbers By

This parameter enables you to renumber the frames output from the node by creating an offset from the first frame number. The "Output Frame Range" display, located just below this parameter, updates automatically as the offset value is adjusted.

To create an offset, key an integer value into the data entry field. (By default, the offset is 0.) The value you enter is added to the current starting number: positive values increase the starting number, while negative values decrease it.

Say, for example, that you load an eleven-frame sequence numbered "file.0040.cin" to "file.0050.cin." By setting a negative offset of 39 (that is, -39), you would remap the sequence such that frame "0040" becomes accessible at frame 1 within Chalice, instead of at frame 40. Frame "0041" would remap to frame 2, and so on.

Note:
Adjusting the frame offset will not instruct Chalice to ignore gaps in the source sequence. An error message indicating that a frame file on disk is missing will still be generated; only the frame number at which the error occurs is offset.

Swap Parameter Tab

The Swap tab enables you to modify channel data in your Disk Input image. You can add channels, delete channels, and rearrange the channel configuration. (This is essentially the same functionality that is available in the Channel Swap node.) A common use of this feature is adding an alpha channel to an RGB image.

Channel Controls

Check this box to enable the channel configuration parameters to receive input. If this box is not checked, you will not be able to alter the channel data.

Channels Out

The Channels Out parameter allows you to alter the number of channels in the image. You can key in a number directly or use the tuner dial. An image must contain at least one channel and cannot exceed ten channels.

To rearrange the configuration of the channels, click and draw a connector line from the output channel (on the right) to the input channel (on the left).

Luminance

This parameter allows you to specify the type of luminance (Film, NTSC, or PAL) Chalice will calculate if luminance has been selected as an output channel. For more information on channels and luminance, see the Channel Swap Node description in chapter 13, "Tool Nodes ."

DPX and Fido Parameter Tabs

The DPX Parameter Tab and the Fido Parameter Tab both feature the same set of parameters to facilitate the conversion of these Cineon 10-bit log formats to 16-bit or floating point linear space. (If you need to convert log files to an 8-bit linear data representation, use the Bit Reduce Node .) Therefore, both tabs are described here, illustrated by the Fido Parameter Tab.

Convert

By default, the Disk Input node converts Cineon log files to 16-bit linear using the "remap to 16-bit" option. The Convert parameter enables you to select another conversion option from the popup menu.

You can choose not to convert the data by selecting "None" from the conversion menu, as when it is necessary to demote the file to 8-bit space using the Bit Reduce node or when you want to perform an operation on the log data.

Or, the Cineon log files can be linearized to 16-bit or floating point colorspace by using one of two methods:

  • Use the Cineon Softclip algorithm to remap the log space to 16-bit (the default) or floating point.
  • Use the strict Cineon Linear conversion to insert the log data into 16-bit or float space.

Using "Remap to"

The default conversion is Remap to 16-bit , which stretches the log data in a constant curve to fill the 16-bit space. The Remap to 16-bit and Remap to Float options use the Softclip conversion method, which clamps values above Log White.

Note:
Depending on your imagery, you may want to adjust the Softclip parameter for the Remap options. When the Softclip parameter setting is left at its default of 0, the Log 90% White parameter value is mapped to 65535 in 16-bit, and to 1 in float.
Positive Softclip values create a breakpoint below 90% White, above which the slope of the conversion curve is "softened" to reduce clamping of the highs.
For a complete description of the Softclip conversion process, refer to the Bit Reduce Node description in chapter 14, or to appendix C, " Softclip Conversion ."

Using "Insert into"

The Insert into 16-bit option converts Cineon log files to "Cineon Linear." The insert method is a strict conversion that does not stretch the data to fill the 16-bit space. Instead, the Log 90% White value (the default is 685) corresponds to the Linear 90% White value, which has a default value of 4095. Log values above 685 are not clamped when converted.

Note:
Setting the Linear 90% White value at 4095 is why Cineon Linear imagery will look indistinct or black in node monitors unless the default monitor display values are changed. To view Cineon Linear, select one of the Cineon display LUTs or the Cineon Monitor Preset (see chapter 8, "Monitors and Flipbooks ," if you need more information about monitor display parameters).

The Insert into Float option linearizes the log data by inserting it into floating point space without clamping float values at 1 (as the Remap to Float option does).

Conversion Parameters

The following chart shows which parameters are applicable to each option in the Convert menu:

All four conversion methods use the Log 90% White and Film Gamma parameters. The two Remap options use the Reference Black, Display Gamma, and Softclip parameters. Only Insert into 16-bit uses the Linear 90% White parameter. The values in the chart represent default parameter settings.

Note:
All of the default values for Cineon conversion are based on specifications published by the Cinesite Digital Film Center and Kodak Motion Picture & Television Imaging. These documents are available for downloading in Acrobat format from the Silicon Grail website (www.sgrail.com).

Log 90% White

The Log 90% White parameter enables you to modify the default RGB log values of 685 for the 90% white card.

Film Gamma

The Film Gamma parameter enables you to modify the default RGB conversion values (0.6) for film gamma. (The slope of the straight-line portion of the characteristic curve for typical negative film is known as the film gamma.)

Linear 90% White

The Linear 90% White parameter enables you to modify the default RGB linear values of 4095 for peak white (used in the default conversion to 16-bit linear color space).

Reference Black

The Reference Black parameter enables you to modify the default RGB log values of 95.

Display Gamma

The Display Gamma value is used in the Softclip conversion algorithm. The default value of 1.0 should not need modification in most cases.

Softclip

The Softclip parameter enables you to modify the default RGB values to reduce the effects of harsh clamping at the high end when remapping log data. The default value is 0 (no softclip). The Softclip parameter can be adjusted in the range of 0-100.

When the Softclip is a positive value, the softclip value is subtracted from the Log 90% White value to create a breakpoint below peak white. The slope of the distribution curve above the breakpoint is changed to remap the highs more gradually.

Tip:
Middle-click and hold one of the Ladder Bars for any parameter to adjust all three fields (R, G, and B) simultaneously. Ladder bars are the small horizontal bars connecting the RGB fields.
Move the mouse vertically to select an increment value from the Ladder popup, and then move it horizontally at that rung to change the values in the RGB fields by the chosen increment.

Maya Parameter Tab

The Maya parameter tab is provided for users who need to import five-channel (RGBAZ) Maya IFF (.miff) imagery. These Maya image files store the RGBA data as 8- or 16-bits per channel and the Z-depth (ZBUF channel) data as floating point.

To resolve the conflict such a mixed-depth image file would cause in Chalice, you must use the Read Data parameter to specify whether the RGBA channels or the ZBUF channel should be imported into the Disk Input node.

Tip:
To access all five channels of data, select the same file sequence in two different Disk Input nodes and specify RGBA in the Maya tab of one node, and ZBUF in the Maya tab of the other.

YUV Parameter Tab

When YUV colorspace data is imported into Chalice, it is converted to floating point RGB data. However, because of the way YUV data is encoded, the conversion to RGB can result in negative numbers. Therefore, if the floating point RGB data is converted to 8-bit, any negative values will be lost. The YUV parameter tab enables you to specify how this data will be represented within Chalice.

Click the Represent As menu button and select one of the following options: 8-bit, 16-bit, or Float. The default is to represent YUV files as 8-bit per channel data.

ZPIC Parameter Tab

ZPIC is the SoftImage file format for z-depth channel data. Unfortunately, ZPIC files do not contain the necessary information in the header to enable Chalice to determine their resolution. The X Resolution and Y Resolution parameters in the ZPIC tab enable you to tell Chalice the resolution of the ZPIC file being imported.

Be aware that in some cases black space is omitted from the ZPIC file when it is written, which can have the effect of changing the resolution from what it was originally in SoftImage. The size entered in the Resolution parameters must be the size actually saved by SoftImage. Hopefully, the associated RGB file resolution can be referenced for the ZPIC file.




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Copyright 1996-1999 by Silicon Grail Corporation