UM:Dvo Effects Dvo Grain

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DVO Grain

Digital Vision DVO Grain algorithm is specifically designed to manage the look of film grain and to reduce unwanted electronic noise in film or video originated material. Uses include restoration, compression pre-processing, and image processing of new feature film, television and commercial material.

 

The Grain algorithm incorporates the Digital Vision Emmy award-winning PHAME advanced motion estimation technology along with edge-preserving 3-D spatio-temporal filters and temporal (recursive) filters to allow artists to produce clean, sharp pictures and to match the look of film grain from shot-to-shot (including grain matching for underexposed film). The process of adaptively selecting the best mix of spatial and recursive filtering for each pixel is unique to the DVO Grain algorithm.

 

This effect has four groups of parameters:

 

ch-dvo_Grain_buttons-Basic_mode

The Enable toggle button allows the complete effect to be turned on or off.

 

Basic mode - basic settings for a quick de-grain
Processing - specific processing options
Key - keyed settings for chroma adaptation
Setup - settings for various processing selections

Basic Settings and Presets

ch-dvo_Grain_buttons-Basic_mode

 

The DVO Grain Basic mode provides simple control of the grain/noise reduction without sacrificing  performance. Basic mode is a good starting point before using the more advanced settings in the Processing and Setup tabs (if necessary).

 

ch-dvo_Grain_basicmode_settings

Enable Basic

The Enable Basic toggle button allows you to enable/disable DVO Grain basic mode.

 

dv_note

When you edit any of the settings in the Processing or Setup tabs basic mode becomes disabled automatically. Similarly, when you select a Mode from the basic modes, all settings in the Processing or Setup tabs will be adjusted automatically to fit the selected mode and basic mode will be automatically enabled.

Presets

The Mode sets a basic preset level of grain reduction :

 

Values :

Default, Film fine (or video), Film medium, Film coarse

Default :

Default

 

dv_note

Default is roughly equivalent to Film medium

Strength

The amount of grain/noise reduction is automatically set up in the basic mode. This slider control allows you to tune this, and increase or decrease the amount of grain reduction done.

 

Range :

-2 to 2

Default :

0

Out Mix

The Out Mix control determines the mix between the processed image (with grain removed) and the input image to give the final output image.

 

dv_note

This makes it possible to mix in some of the original grain into the processed picture for a better film look.

 

 

Range :

0 to 100

Default :

100%

 

The default value of 100% results in an output with full grain removal, whilst a setting of 0% results in an output equal to the input image.

 

This control is also available in the Processing section and changes here are mirrored there.

Processing Filters

ch-dvo_Grain_buttons-Processing

 

Temporal and spatial filters are available on the Processing screen.

 

DVO Grain utilizes a process that adaptively selects the best mix of spatial and temporal (recursive) filtering for each pixel.

 

dv_note

Start with the basic mode enabled, selecting the most appropriate setting. If necessary,  adjust the processing by disabling basic mode and continuing to the more advanced settings. In many cases, advanced mode will not be necessary.

Temporal Filtering

ch-dvo_Grain_processing_tstrength

 

The temporal or recursive filtering is the most effective filter in terms of reducing grain/noise.

Temporal Strength

Use the numeric sliders to set the amount/level of temporal recursive filtering in each channel.

 

Range :

0 to 15

Default :

7

 

dv_note

Do not use higher settings than 11-12 except in extreme situations. Also note that both Chroma trim and Pos/Neg trim (see below) will add their values to these set strengths.

Temporal Global

Use this toggle button to turn Temporal Global on/off.

 

Default :

Off

 

The DVO Grain is an adaptive grain and noise reducer. This means it disables the temporal/recursive processing of all moving edges within the image to assist in the reduction of motion artifacts.

 

Temporal Global enables filtering of the whole picture regardless of motion for maximum temporal filtering.

 

dv_note

Temporal global should normally be set to Off and only used in extreme situations, or to create a motion smearing effect.

 

dv_alert

Enabling Temporal Global might cause excessive smearing in the picture.

 

In addition to the above controls, the motion sensitivity control on the Setup section adapts the temporal filtering in respect to grain size and intensity

Spatial Filtering

 

ch-dvo_Grain_processing_spatial

 

Edge-preserving spatial filtering complements the adaptive temporal filters by processing grain and noise in portions of the image that are detected as being in motion, while leaving non-moving areas unaffected. The spatial filtering is done before application of the temporal filters and works in unison with DVO Grain’s motion processing.

Spatial Strength

This is the overall level of spatial filtering applied in each channel. Normally, they should match the temporal strength.

 

Range :

0 to 15

Default :

7

Spatial Size

The Spatial Size drop-down lists adjust the spatial size of the grain/noise, in pixels, for each channel.

 

Values :

1,3,5,7,9

Default :

7

 

dv_note

Setting R, G, B spatial size equally will give best performance

Spatial Threshold

The spatial threshold determines when to filter, depending on the intensity of the surrounding pixels.

 

Range :

0 to 100

Default :

7

 

Use the spatial threshold sliders to adjust the setting for each channel.

 

If there is a high enough intensity/contrast (e.g. an edge) between the grain/noise and surrounding pixels, filtering will not occur.

 

dv_note

A low setting will only affect low intensity pixels (flat areas). A high setting will start to affect high intensity pixels (edges)

Spatial Global

This enables filtering of the whole picture by switching off the motion adaptation.

 

Use this toggle button to enable/disable global spatial filtering.

 

Default :

Off

 

A moderate level of global spatial filtering can be used as a basic level of grain and noise reduction before using the temporal filtering (also see Global Balance).

 

dv_alert

This may cause excessive softening of the picture if the spatial filter is not set up correctly.

 

dv_note

Temporal filtering works in areas with no or little motion.

Spatial filtering works in areas of motion.

Global enable the filters to work on the entire picture.</br></br>

 

dv_note

The R, G, B Strength controls should normally be ganged and adjusted together. They typically need to be adjusted by the same amount.

Optimising the Spatial Filter

1.Set Spatial Strength, Size and Threshold to their maximum
2.Turn Spatial Global on
3.Adapt the spatial filter to the grain/noise size by decreasing the spatial size settings to as low as possible whilst still resulting in grain/noise being removed
4.Decrease spatial threshold until edges are not affected (a typical setting is  between 8-20%)
5.Decrease spatial strength until the desired level of spatial filtering is achieved
6.Decide whether Spatial Global should be left on (filtering of the whole picture), or turned off (filtering only in areas with motion).

 

dv_note

Starting with enabling Basic mode and selecting one of the available preset modes will automatically set up spatial threshold/size

Chroma Trim

ch-dvo_Grain_processing_ctrim

 

The Chroma Trim controls are used to adjust the grain/noise reduction on each selected colour. This allows for the boosting or cutting of both the spatial and temporal filter settings within the selected colour.

 

Range :

-8 to 7

Default :

0

 

The colours 1, 2, 3, are selected via the key tab, as described in the Chroma Adaptation section below.

 

dv_note

Having a temporal strength of 7, setting up chroma adaptation for a red colour and corresponding trim to +2, will set the temporal strength to 7+2=9 for areas in the picture that contain the selected red colour.

Other

ch-dvo_Grain_processing_other

Pos/Neg Trim

The Pos/Neg Trim control works in conjunction with the Pos/Neg mode controls in the Setup section. Having selected the mode and luma thresholds in the Setup section, use the Pos/Neg Trim control to adjust the noise reduction levels equally for all RGB channels in highlights (Neg) or lowlights (Pos).

 

Range :

0 to 7

Default :

0

 

dv_note

Having a temporal strength of 7, setting up neg mode to neg and the pos/neg trim to +2, will set the temporal strength to 7+2=9 for highlights.

 

dv_alert

Processing is slower using trims. Even if Temporal/Spatial strengths are at 0, Pos/Neg Trim will still add to this and result in processing within highlights or lowlights.

Out Mix

This control is the same as the Out Mix control available in the basic mode tab, and changes here are mirrored there.

 

Range :

0 to 7

Default :

0

Global Balance

Global Balance allows a combination of the basic level of spatial filtering and motion adaptive spatial filtering.

 

Maximum filtering according to spatial strength is achieved in areas with motion.

 

The Global Balance slider allows you to to set a minimum level of spatial filtering, rather than having the level set entirely based on motion detection. If the slider is set to 0, then parts of the image with no motion will receive no spatial filtering.  Increasing the slider increases the spatial filtering of areas with little or no motion.

 

Range :

0 to 100

Default :

50

Motion Estimation

DVO Grain is a fully motion compensated noise/grain reducer. This means that much more aggressive settings can be used without introducing smearing.

 

The motion estimation drop-down button allows you to set the motion estimation to :

 

Range :

Off, Normal, Best

Default :

Normal

 

dv_note

The Best setting is good for fast motion but is slower than Normal. In almost all cases, Normal or Best should be used.

Key (Chroma Trim)

ch-dvo_Grain_buttons-Key

 

The Key (chroma adaptation) function can be used to adjust the levels of grain/noise reduction in user selectable colour regions.

 

dv_note

For example, this feature can be used for greater grain/noise reduction in sensitive areas such as a blue sky, or less noise reduction in skin tones.

 

Three independent channels of chroma adaptation allows adjustment of noise reduction levels (both spatial and temporal) in the regions of the selected colour.

 

These selectable colours are labelled 1, 2 and 3.

 

dv_note

Only colours with a saturation higher than approximately 5% will be detected.

 

Use the Key screen to adjust the hues and widths to isolate the colours in each channel:

 

ch-dvo_Grain_key_all

 

Click a colour picker toggle button to enable/disable colour picking from the displayed monitor image :

 

Enable picker

ch-dvo_Grain_key_picker_on

Pick area of colour from image using the mouse

ch-dvo_Grain_key_picker_select_area

 

You can also select the selected hue by clicking on the hue bar with the left mouse button and dragging the hue bar left and right :

 

ch-dvo_Grain_key_hue_bar

Drag on hue bar and/or orange box indicators to alter hue selection.

 

After selecting the colours using the key tab, the corresponding Chroma Trim control in the Processing tab may be used to adjust the grain/noise reduction for each selected colour. Chroma Trim allows for the boosting or cutting of both the spatial and temporal filter settings within the selected colour.

 

dv_note

Even if Temporal/Spatial strengths are at 0, Chroma Trim will still add to that number and resulting in processing within selected colour.

Setup

ch-dvo_Grain_buttons-Setup

 

The Setup screen allows various other effect parameters to be configured.

Colour

ch-dvo_Grain_setup_input_format

 

The drop-down list will default to the project setting for the input format. You need to set this control according to the material that you are working with. If the footage was shot with a video camera, select a linear format. If this control is not set correctly the material may not be processed properly.

 

Default :

From Project

History Required

ch-dvo_grain-setup-history

 

The DVO Grain effect is recursive.

 

dv_note

Recursive means the result for any given frame depends on the result of the previous frame(s).

 

For best results a certain amount of frame history needs to be built up, and this numeric slider is used to specify how many frames of history to use.

 

Range :

0 to 15

Default :

5 frames

Use Handles

ch-dvo_grain-setup-handles

 

The Use Handles button controls whether the history includes available handles of a scene/shot. Normally, the history frames accumulated will terminate on a shot edit/event (start/end edit). There may be extra frames available (handles) before or after the start and end edit points of a shot however and these will be included as history if Use Handles is set.

 

dv_note

If handles exist, full and precise processing will be available from the first frame of a clip.

 

Default :

On

 

The remaining controls on the Setup page are used to optimise the processing further. These controls should only be used by experienced operators with a good understanding of the dirt and scratch concealment process

Motion Sensitivity

ch-dvo_Grain_setup_motion_sensitivity

 

This drop-down allows you to set the level of sensitivity.

 

Values :

Low, Medium, High

Default :

Medium

 

Motion sensitivity adapts the temporal filtering with respect to grain size and intensity.

 

dv_note

Motion sensitivity has great impact on processing and the type of filter (spatial/temporal) being used.

 

dv_note

It may be better to set Motion Sensitivity to Low rather than just increasing filter strengths.

Spatial Filter

ch-dvo_Grain_setup_spatial_filter

Spatio - Temporal

Enabling this extends the spatial filter to become a 3D spatio-temporal filter, by including the use of temporal taps. This can enhance the noise reduction achieved.

 

Default :

On

Temporal Mix

The temporal mix controls the balance between the spatial and temporal taps of the spatio-temporal filter.

 

Values :

Low, Medium, High,Full

Default :

High

 

This setting affects the noise reduction achieved by the spatio-temporal filter, with more noise reduction for the higher settings.

 

For fast motion material and a higher than default spatial filter threshold setting, a high temporal mix setting may increase the probability of artifacts. In such cases, this setting may be lowered. For a lower than default spatial filter threshold setting, the Full setting may be used.

 

dv_note

The default setting High should be safe in most circumstances.

Spike

This setting enhances the spatial filter performance by incorporating a spike adaptation.

 

Values :

Off,Narrow,Medium,Wide

Default :

Medium

 

The setting relates to the grain/noise characteristics. A low setting (e.g. Narrow) is suitable for smaller grain and noise sizes and/or less pronounced variations in  amplitudes.

 

A high setting (e.g. Wide) is suitable for larger grain/noise and/or more pronounced variations in amplitudes.

 

dv_note

Setting spike to Narrow in conjunction with setting Motion Sensitivity to High and Motion Estimation (in the Processing screen) to Best can help avoid motion estimation errors caused by noisy / grainy material.

Pos/Neg Profile

ch-dvo_Grain_setup_pos_neg

 

The Pos/Neg profile allows the user to select the amount of noise reduction (both spatial and temporal) applied to the highlights or lowlights within the image.

 

dv_note

This function is important when dealing with grainy images in positive or negative film stock.Positive film will generally show more grain in the lowlights whilst Negative film will generally show more noise in the highlights.

Neg

Values :

Positive,Negative

Default :

Positive

 

Parameters :

 

Positive - more grain reduction in lowlights
Negative - more grain reduction in highlights (Film mode)

 

Having selected the mode, you need to set the Pos/Neg Trim level on the Processing screen. This will adjust the noise reduction levels equally for all RGB channels in highlights (Neg) or lowlights (Pos).

Luma Thresholds

The range of luminance values affected by the Pos/Neg Trim can be set by two luma thresholds.

 

Luma Threshold Low

Range :

0 to 50

Default :

0% Luma

Luma Threshold High

Range :

50 to 100

Default :

100% Luma

 

These two thresholds determine the point in highlights and lowlights where the Pos or Neg trim is at its maximum.

 

The effect of the Trim will gradually decrease between these two points.

 

ch-dvo_DVO Grain Pos trim

Trimming the Grain/Noise Reduction level for Positive film

 

ch-dvo_DVO Grain Pos low threshold

Trimming the Grain/Noise Reduction level for Positive film

 

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