Tips: De-interlace video

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Always De-interlace Video!

We have repeated many times, always de-interlace video first! Deinterlaced video will facilitate both enhancement and other post-production tasks.

Here are some tips:

• Always use filter Deinterlace* to de-interlace an interlaced video. Don’t use “Separate Field” option in After Effects, which will produce lower resolution result. Don’t use a 3nd party de-interlacer since it might not work well together with other filters in Topaz Enhance.
• Don’t apply any other filter, of Topaz Enhance or others, before filter Deinterlace*, with only one exception. If you need remove compression artifacts, you should use filter Remove Compression Artifacts before applying Deinterlace*. However, make sure to use frame mode processing.
• Even if the frame is noisy, still de-interlace first and de-noise it later. In fact, filters such as Denoise & Enhance* and Clean (YC)* can only be used on de-interlaced video.

Double Frame Rate or Not?

During De-interlacing video using Deinterlace* filter, you have the option of doubling the frame rate. For example, an NTSC DV clip at 29.97 FPS. can be de-interlaced as a progressive video at 59.94 FPS with perfect smooth motion. Basically the filter will produce a progressive frame from each field.

Now the obvious downsides of doubling the output frame rate is that Deinterlace* filter takes twice as long to process comparing to not doubling the frame rate.

We recommend that you double the frame rate in situations like these:

• You are going to use one or more of the inter-frame filters, i.e., Denoise & Enhance*, Clean (RGB/YC)*, or Double Resolution*.
• Somewhere you will need to change the frame rate for the footage according to none-integer ratio, for example, 29.97fps to 25fps or 29.97 fps to 24 fps.
• You need to use time-warping effect to speed up or slow down motion and you want the result has smooth motion.

Examples

Suppose you have an NTSC DV clip at 29.97 FPS. You want to remove noise from it and produce a 720p HD footage. Here are the steps to do it (The follow steps only apply to After Effects!)

1. Create a composition “comp_DI” at exactly 59.94 (2x29.97) FPS and put the clip into it. Apply filter Deinterlace* to de-interlace it and double its frame rate.
2. Create another composition “comp_Denoise” at 27.97 FPS, and put “comp_DI” into it. Now you can apply filter Denoise & Enhance* to it. Now you have a clean video.
3. Create another composition “comp_2X” at 27.97 FPS and 1280x720 in size. Put “comp_Denoise” into it and apply filter Double Resolution*. Now you can create a HD video from DV if you render composition “comp_2X”.

Notice here that we first double the FPS at step 1 during de-interlacing, but go back to the original frame rate at step 2 and 3. In this way, the filters Denoise & Enhance* and Double Resolution* operate at 29.97FPS instead of 59.94FPS. This will reduce processing time while still maintain high quality.

Now, suppose you want to convert this NTSC clip to HD at 720p and 24 FPS, you can simply change the frame rate of composition “comp_2X” at step 3 to 24 FPS. Everything will work perfectly. In fact the processing will be a little faster since there are fewer frames to produce at step 3.

You may notice a little drawback by the above approach, however. You may notice not –so-smooth movement in some scene. This is because the frame rate change at step 3 from 29.97 FPS to 24 FPS is done by selecting the closest frames.

If you want to have the best possible quality, you should use double frame rate in enhancement and only convert to 24 FPS at the last step:

1. Create a composition “comp_DI” at 59.94 (2x29.97) FPS and put the clip into it. Apply filter Deinterlace* to de-interlace it and double its frame rate.
2. Create another compostion “comp_Denoise” at 59.94 (2x29.97) FPS, and put “comp_DI” into it, and apply filter Denoise & Enhance* to it.
3. Create another composition “comp_2X” at 24 FPS and 1280x720 in size. Put “comp_Denoise” into it and apply filter Double Resolution*. Now you have HD 720p video at 24 FPS.

In summary,

• You should use either the same FPS or double the FPS of the input footage in all the enhancement steps, except the last one. The last filter, as in step 3 of the two examples, can change the frame rate to any rate.
• Use the double frame rate to get the smoothest motion.

You generally don’t need to double the frame rate in the situation like: