Deinterlace video shots

Interlaced video shots are difficult to track, especially if the camera moves a lot or moves quickly. For best results, deinterlace your images before attempting to track the shot.

Since there are many ways to deinterlace images, the best two methods are described here.

Interpolate scanlines on both fields

The best way to deinterlace is to use a utility that separates the even and odd fields into an image per field, and then interpolates the empty scanlines using neighboring scanlines.

On Windows

Use any video editing or compositing tool that can separate the fields by interpolating the empty scanlines using neighboring scanlines.

On Linux

Maya on Linux includes a utility called delace for this type of deinterlacing. For example, to deinterlace a sequence of images called sand.*.rgb, type the following command in a shell:

delace sand.rgb.0001 sand_fields.rgb.#

Before tracking, be sure to set the Time unit in Maya to the rate for fields (for example, 50 fields per second). Use the Window > Settings/Preferences > Preferences, in the Settings category. As you work, remember that you are working with separate fields, not frames.

Delace options

The Linux delace utility also includes these option flags:

-s option: Specifies to use smoothing. With smoothing, the interpolation references neighboring frames as well as the scanlines. This option can improve results in sequences with slow camera movement, but it can cause undesirable artifacts in sequences with fast camera movement or fine detail.
-e option: Specifies that even scanlines in each image represent the first field in the frame. The result is an even scanline image followed by an odd scanline image. This flag is the default.
-o option: Specifies that the odd scanlines in the image represent the first field in the frame (the opposite of -e).

For example, to specify smoothing, type:

delace -s sand.rgb.0001 sand_fields.rgb.#

Interpolate scanlines on half of the fields

The next best way to deinterlace is to use the dmconvert utility (available on Linux only). The utility separates the even and odd fields, throws one of them away, and interpolates the empty scanlines using the neighboring scanlines.

For example, to deinterlace an NTSC video shot, type the following command as one line. Replace in.*.rgb with your source image name. If you are using PAL video, replace inil=odd with inil=even.

dmconvert -v -f rgb -p video,inil=odd,il=none -n out.####.rgb,start=1 in.*.rgb out.####.rgb

Because dmconvert throws out the even or odd fields, you must set the Time unit in Maya Live to the frame rate (for example, 25 frames per second) instead of the field rate (for example, 50). Use the Window > Settings/Preferences > Preferences, in the Settings category. However, when you render, you will probably use the field rate.

The problem caused by solving at the frame rate is that the movement is interpolated for the missing field. The match should be close, but you might have some slippage on the fields which were discarded.