AVX Plug-Ins
(Show frame with Topics and Control Panel)
User Guide"Tips" appear in green. Tips
will save you time but are not essential information.
"Cautions" appear in red. Be sure to read and understand this information.
3Prong's DirtFiX AVX Plug-in allows you to fix most video dropouts, film dirt, and other transient defects within Avid editing systems.
You move a box over the defect, then add a keyframe to each defective field. DirtFiX patches over the defect using the clean portion of the previous field or frame, or using a similar portion of the current field.
If needed, you can move or resize the patch in subpixel amounts to match camera movement or movement in the scene. You can also feather the edge to blend the patch seamlessly.
DirtFiX is similar in theory to the Scratch Removal feature found on later and higher-end Avid systems, but there are some important operational differences.
There are several ways to use DirtFiX, but this is the most common way:
- Add an edit close to the defect.
- Apply a DirtFiX effect to the cut as a transition effect.
- Drag the Target box to cover the defect.
- Add keyframes to each defective field.
- If there is motion in the Target area, step back two fields and forward again to load the cache, then toggle the Bypass button to help you adjust the Shift controls for a good match.
- Render.
You do not need to find the exact location of a defect before you apply the DirtFiX effect to a segment or transition, but it helps to be within a frame or two. After you have applied DirtFiX, you will then need to find the exact defective fields within Effect mode.
When stepping frame by frame through the sequence with the arrow keys in Source/Record mode, you see only one of the two fields that make up each frame. The default is field 1, and field 2 is not shown, so you will be unable to find any video dropouts that are only on that field. (Film dirt is easier to find since a single film frame lasts for 2 or 3 video fields.) To get around this, use the single-field step buttons:
You may mark individual defects or bad clips with locators, and later return to repair problems by double clicking inside the locator tool window. (Note that locators are frame-accurate, not field accurate, so you might have to step forward a field to see the problem.)
When you apply an unlicensed 3Prong AVX Plug-in, you will see an "outlet" logo in the middle of the image. This shows that the plug-in is operating in trial mode. The logo will disappear after the plug-in is licensed and unlocked.
DirtFiX effects can be applied either to transitions (cut points in a sequence) or to segments (clips used in the sequence.)
A transition effect is recommended for isolated defects, because it will minimize the
number of frames to be rendered. Usually a duration of two or three frames will be
sufficient. Film dirt is a little longer in duration than most dropouts. It’s better
to be a little too long than too short, because if you
extend the duration later, any keyframes will shift proportionally in timing and may move
off of the defective fields.
Park on or near a defect in the sequence, and add an edit. Then drag the DirtFiX effect
icon from the Effect Palette and drop it on the edit in the timeline.
Choose "centered" for the transition. If an "Insufficient Source"
warning pops up, click on "size to fit". Then shorten the effect duration so
that it is as short as possible while still encompassing all the defective fields. Power users will avoid this step by saving a three-frame duration
effect template to apply directly from a bin.
Add edits for several defects, and you can apply one DirtFiX
effect to them simultaneously. In Effect mode, select the edits by
lassoing from left to right in the Timeline. If the desired transitions are not
contiguous, <Shift>-click a transition to select or deselect it. Double-click the
shortened DirtFiX effect template in the bin, and you will see it applied to all the
selected edits. Then adjust them individually as required.
To cover a flash-field or other defect at the head of a
segment, you can use a transition DirtFiX effect on a cut between the two
different clips, even though it is not a match-frame edit. You must set
the effect to be centered to ensure that you retain the correct cut point. Then,
the last field or frame of the outgoing clip is available as a cache source to repair the
first field of the incoming clip. Use Field Cache and enlarge the Target area to cover the
entire image. This extends the previous clip by a repeated field.
Use a segment effect when there are a lot of defects within a single segment. Simply drag and drop the DirtFiX icon from the Effect Palette onto the segment.
Though only those fields with keyframes are altered, the entire segment must be
rendered, so consider adding edits to
isolate the problem section first. Adding edits will also separate the DirtFiX effect from
the head and tail of the shot, allowing later trimming without changing the length of the
DirtFIX segment which would move the keyframes off the defective fields.
If you are having trouble selecting a very short segment, lasso
the segment before entering Effect mode.
You may apply a DirtFiX effect to a filler segment on the
track above your video. Place add-edits in the filler to create a filler
segment above the defect. This trick is useful in a few situations:
In Effect mode, using the left and right arrow keys, step field by field to locate the first of the defective fields. You will see the Target box near the middle of the image. Drag the entire box (or individual corners of the box) to cover the defect. <Alt>-dragging a corner resizes the entire box.
You have a choice of an ellipse bounded by the Target box sides, or the entire rectangular box area. The ellipse is the default shape.
If desired, increase the Feathering slider to blend the patch into the Target area. Ten pixels is usually plenty, but you may select up to 128 pixels of softness. Feathering works outwardly from the Target, so the area inside will always be completely patched.
If you accidentally close the Target box entirely and it disappears, use the sliders in the Effect Editor to open it up again. It does not matter if the sliders pass each other so that the box becomes inverted, as the patch is still applied to the interior of the box.
If there are several defects or a hard-to-match movement
on a field, just extend the Target to cover the entire image. This
repeated field will be hardly noticeable in most video; with film footage it is usually
undetectable.
Avid’s "Big Effect mode" is recommended
to place the Target accurately, because it will show every pixel in the image. This is
only available on timeline monitors with a resolution of 1024 X 768 or greater.
Use Avid's magnification feature
to zoom in and place the Target area (or patch) exactly. In addition to the Effect
Editor's buttons, try the following keyboard shortcuts. (They vary slightly depending on
platform and type of Avid system):
| To do this: | Mac | Windows |
| Magnify at the clicked point, through to maximum and back to normal | <Command>-click | <Ctrl>-click |
| Resets/reduces magnification to normal | <Shift>-<command>click | <Shift><Ctrl>-click |
| Reposition the magnified image within the Effect window | <Option>-<command>drag | <Ctrl><Alt>-drag |
Before adding keyframes to defective fields, try setting the controls such as Target area first. If there are multiple fields with defects in the same location, all keyframes added for them will then have the same settings.
Use the keyboard shortcut to add keyframes while stepping through the effect timeline, (location varies, check your Avid manual). If you instead click on the Effect Editor’s Add Keyframe button, further presses of the arrow keys will then move the selected slider in the Effect Editor instead of continuing to step through the timeline.
Previewing before rendering is usually not needed, since most fixes are on unmoving or non-detailed areas (meaning you will not need adjust the Match controls). The Bypass button allows previewing fixes (providing that Avid's "render on the fly" function is on and the cache is loaded), but Bypass has no effect on final rendering. This means you can leave Bypass on or off for most keyframes.
However, Bypass does affect rendering for the head and
tail keyframes. All Avid effects have head and tail keyframes that cannot
be deleted. Bypass is also used to select whether or not these first and last fields are
meant to be patched. For safety then, Bypass is on by default, so the head and tail
keyframes are not patched, but previews of other fixes are not seen.
In summary, leave Bypass on unless you need to preview the
fix, or patch the head or tail keyframe. Even when Bypass is on, you can
still preview by stepping forward
sequentially forward through the fields.
"Current" uses the current field as the Source for patching the Target. Of course, replacing the Target area with itself produces no change in the output (until the source image is shifted using the Match controls).
When Current is selected, a green box appears which shows the area of the image used as the Source. This Source box cannot be dragged directly, but is adjusted by moving the Match controls. The Source box display is suppressed during rendering.
Frame or Field use a previously cached image as the Source for the patch. Frame cache uses the same (odd or even) field from the previous frame, in other words, two fields prior to the target field. This is ideal for film or other progressive-scan material where there is no action between fields of the same frame, as the Source needs no conversion from one field type to the other. Generally, defects which go on for more than a single field should be patched using Frame Cache.
Field cache uses the field immediately previous to the Target field. Field Cache is most suitable for single-field defects like dropouts in video-camera footage with a lot of action because the Source field is closer in time to the target field and it is more likely to have captured similar action. However, the field is the opposite type (odd or even) to the target, so it will be converted (in the way set by the Field Compensation button).
Avid’s AVX v1.0 does not normally allow plug-ins to access fields other than the current one. DirtFiX for AVX 1.0 relies on the sequential rendering to cache any fields required for the "Cache" settings. The cached field is only available when the required Source field was rendered just prior to the current one.
If you see a color negative highlight in the Target area, a preview cannot be shown because the previous field or frame is not cached at that moment. Instead, the highlight helps to set the Target and Feathering.
Since the head keyframe of an effect has no previous field, it can only be patched with Current as the Source. There will be no patch when either Frame Cache or Field Cache is selected. Likewise, the second field of an effect cannot be patched with Frame Cache selected.
Note the rendered output of DirtFiX is cached and not the original image, so that defects fixed in previous fields do return in the new fix.
When using a cached source and there is motion in scene or when to use another area of the current image as the source, use the Match controls to align the patch within the Target area.
Turn Bypass off to see the patch. If Frame Cache or Field Cache is the Source, and the Target area shows an inverted highlight, you will have to step forward from the Source field (where the cache is loaded) to the target field.
It is best to think of the H Shift and V Shift controls as moving the patch within the Target box. If you are instead looking at the green Source box, it appears to move in the opposite direction to the H Shift control.
The Size control helps to compensate if the camera was zooming or the subject-to-camera distance was changing. It is sub-pixel rendered so you can track the finest zoom.
To adjust the Match controls for the best positional alignment, try these techniques:
You may notice a difference in control sensitivity depending on the Source you have selected:
If the Match controls move the patch beyond the edges of the Source image, that portion
of the patch will not be visible. If you don't see your
patch, especially when the Source is set to Current, you have probably moved the H or V
shift controls too far. Try resetting them to zero and making smaller
adjustments.
Field Compensation sets whether a Field Cache
image is interpolated to match the Target field, which improves the spatial alignment but
softens the patch slightly. Field Compensation has no effect when Source is set to Current
or Frame Cache. Field Compensation may generally be left on. However,
if consecutive keyframes patch the same Target area with Field Caches, repeated Field
Compensation of the Source image will cause it to degrade. Use Frame
Cache, or turn off Field Compensation.
When patching film dirt with 3:2 pulldown, use Frame Cache. The
third field of a film frame should have the H and V Shift controls set to zero,
because its Source is the first field of that same film frame. Set these by clicking on
each Shift control and typing<0><Enter>. (Disabling the Match group will turn
it off for the entire effect, not just a particular keyframe.)
DirtFiX is similar in theory to Avid's Scratch Removal feature, and is designed for users who lack this feature (Avid Xpress DV users, Media Composer 7.x users, and others). However, even users who have Scratch Removal might like to use DirtFiX at times. Here is a summary of the differences between DirtFiX and Scratch Removal:
DirtFiX is designed to Avid's AVX 1.0 specification in order to be useful on the majority of Avid systems. Skillfully used, you can seamlessly repair the vast majority of dirt and dropout problems, as well as many film splice shifts, booms in shot, camera flashes, EMF "zits", and other such problems. However:
| Description of Problem | Possible Causes | Possible Solutions |
| Patch not visible. | No keyframe present. | Add a keyframe and adjust parameters. |
| Bypass is on for current keyframe. | Turn Bypass off. | |
| Cached Source is not available at head of effect. | First field of an effect cannot have Field Cache or Frame Cache as a
Source, only Current. Second field cannot have Frame Cache as a Source, only Field Cache or Current. |
|
| Field not rendered. | Render on the Fly is set to off. Turn it on in the Avid Clip menu. | |
| Effect just applied, so AVX has not yet rendered. | Adjust any control. AVX will render the image. | |
| Wrong video track being monitored. | Switch monitoring to the effect track. | |
| Patch is shifted beyond edges of Source image. | Reset H and V Shift sliders to near zero. Then move them in smaller amounts. When Source is set to Current, keep the green source box in frame. | |
| Patch shows inverted color highlight. | Cache is empty. | Step back 1 field to load Field Cache, or 2 fields to load Frame Cache, then forward again to the target field. |
| Patch is too bright/too dark/slightly different color. | Flicker: level fluctuations in footage between Source and Target fields. | Use a 3Prong FlickerFiX effect nested inside the DirtFiX effect, and render before rendering DirtFiX. |
| Patch is slightly “soft”, not as sharp as target image. Softens gets worse with consecutive keyframes. |
Field Compensation in use. | Turn off Field Compensation, or if scene motion allows, set Source to Frame Cache. |
| Match controls in use. | Slightly adjust Shift controls to see if sharpness improves while Match is still acceptable. | |
| Erratic operation of keyframes and source patch. | Using a single field AVR | Avid's AVX 1.0 does not work properly with Single Field AVRs. |
| Using Avid Xpress DV or Xpress Pro | Turn off Avid's Real-Time Effects to set up and render DirtFiX. |