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Disguise User Guide

Video De-Interlacing Methods

Designer is able to de-interlace incoming interlaced video.

While Disguise does not recommend interlaced formats, there are a number of options to attempt to reduce the visual artifacts which are visible with these legacy formats. For the majority of cases, using a 720p signal results is better quality imagery.

Interlaced formats consist of time and space separated fields which are half the height of the full progressive frame. These fields contain even or odd lines from different points in time. They are offset from each other by one pixel vertically and by the field rate in time.

De-interlacing methods attempt to reconstruct as close to a true progressive frame as possible from this reduced data. As with all systems which create new data, this may not be what was truly captured in the first instance.

The following de-interlacing methods are available:

  • Discard even

  • Discard odd

  • Bob - Interpolate

  • Bob - Duplicate

  • Weave

  • Weave & Interpolate

  • Weave on odd

  • Weave on odd & Interpolate

  • Weave on even

  • Weave on even & Interpolate

Each of these methods has a tradeoff with different types of content, depending on vertical detail frequency, and horizontal movement.

Accessing the de-interlacing methods

  1. Right-click on the Devices tab in the dashboard.

  2. Left-click on the Video Input Patch Editor.

  3. Select the desired Video Input and expand its properties menu.

  4. Expand the Deinterlace method tab. Deinterlace method

Discard methods

The discard methods discard either the even or the odd field, thus removing 50% of the received data. If this option looks best with the captured data, then consider switching to a lower frame rate progressive signal, as the effective frame resolution is half height and half field rate. Slowly scrolling thin horizontal features can ‘disappear’ into the other field using these techniques, leaving a low frame rate flickering result in the worst case.

Bob methods

The bob methods render every field one by one, enabling full field rate display of the data, but can result in a vertical bobbing motion, especially visible at high contrast edges. The interpolate method is generally less noticeable, due to the fuzzing of these edges. The vertical bobbing motion comes from the contrast between the two fields - if there are a series of red lines, followed by a series of white lines, the area which transitions from red to white will flicker due to the last red line only being visible 50% of the time.

Weave Methods

The weave methods use 2 fields to reconstruct the progressive frame. These methods resolve issues with high frequency vertical features disappearing between fields, but introduce issues with horizontal motion. When horizontal motion is active, and the weaved fields are separate in time (i.e. not PSF) then the change in position during that time creates a comb-like effect, showing the horizontal movement. Against a high contrast background, this is not pleasant.

The interpolating variants of the weave methods attempt to reduce this combing by combining 50% of the most recent field with the older field. When working with moving images, this blurs out the combing effect, and it’s possible to believe the effect is similar to motion blur. However, this method shares similar issues with the bob methods, in that if the most recent field does not have the same information as the line it is being blended with, a darkening effect can occur.

Weave takes the 2 most recent fields, even across different frames, and presents them immediately. This can result in some flickering artifacts with the interpolating method, as the most recent field which was received takes precedence. This is mitigated with Weave on even, which always takes the most recent full frame, and weaves pairs of fields in the same way every frame. The cost here is frame rate, which is halved by waiting for both pairs to become available before showing them.

Weave on even is useful for interpreting PSF formats. Interpolation should not be necessary with PSF, as PSF is effectively an interlaced transport for a progressive frame - there is no temporal offset between the fields.

Weave on odd can be useful if at some point in the upstream signal chain, the interlaced fields have been switched to the wrong order.

Weston 3 Field also known as W3FDIF, is a 3-field vertical-temporal de-interlacing method developed by the BBC and included in ffmpeg.