Nowadays there's a lot of equipment that allows you to store and play HDTV (or simple HD, high-definition) video which has resolution like 1280x720, 1920x1080 etc. And at the same time there's a significant lack of HD content. Majority of TV channels and DVD movies are 720x576 or less (so called SD, standard-definition). So if someone wants to watch SD video on his or her HD screen, upsizing becomes inevitable. Upsizing video can be done with big variety of methods. They differ in quality, complexity and speed. Most screens and video players already have some built-in methods for upsizing content, usually bilinear or bicubic interpolation.

While there are a many methods for in-frame (spatial) upsizing, there is another approach which uses information from different frames to reconstruct more details. This approach is called super-resolution. This topic was discussed by mathematicians for 20 years and now finally our computers became powerful enough for practical super-resolution implementations.

In this article we'll compare different methods of video upsizing that anyone can try - accessible in downloadable software. This means that implementations existing in very complicated form of Matlab or Avisynth scripts or available only as technologies for big companies or in some commercial software not available to try and so on - these methods are not included in this comparison. Also, software which uses super-resolution approach to reconstruct single frames from video (like QE SuperResolution, Topaz Moment, Photo Acute, etc.) is not included.

Included methods:

• Zoom - simplest method of enlarging each pixel 4 times, also called "nearest neighbor".
• Bicubic resize - internal resize filter of VirtualDub, bicubic spline interpolation. Same resize method is used in vast number of players and apps.
• Lanczos3 - same VirtualDub filter, Lanczos3 method.
• Lanczos3+sharpen - sequential application of two internal VirtualDub filters: first Lanczos3 resize and then sharpen filter with its parameter set to 40.
• Video Enhancer - using super-resolution in high quality mode. This technology is also available as Adobe After Effects plugin (see SuperResolution plugin).
• Topaz Enhance - a plug-in for Adobe Premiere Pro 2.0 was used, Enlarge filter with default parameters.
• Instant HD - a plug-in for Adobe Premiere Pro 2.0 from Red Giant Software. Demo variant was used that leaves "watermark" on result, so it was impossible to correctly calculate objective metric (PSNR) for this method.
• DA Resizer sharp - Resizer v2.2 from Digital Anarchy, a plug-in for Adobe After Effects, best sharp mode.
• DA Resizer smooth - the same plug-in, best smooth mode.

Process of comparison

Results

Comments and conclusions

1. PSNR for InstantHD plugin not calculated due to "watermarks". But its visual level of detail is close to Lanczos method. That's interesting because its official site starts with someone's quote "the shots I up-rezzed myself with Instant HD were indistinguishable from those run through the very high end Quantel." That gives us some insight on "very high end" quality. ;)
2. Topaz Enhance shifts video up-left for pixel or half a pixel. This is one of the reasons why it got so low PSNR. Another reason may be making video too cartoon-like, with sharp edges and too smooth gradients that lose all detail.
3. Video Enhancer, absolute winner in PSNR, proves that super-resolution can really be much effective than Lanczos+sharpen, the scheme critics often supposed it used.

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