From 720x480 to 1280x720 Question

Good Day,

I am about to take a 720x480 finished film and move it to a 1280x720 format. I have read this article by Larry Jordan
[www.larryjordan.biz], and I am in the process of converting using his ideas. The process is being done in compressor.

An editor friend has suggested a different method, and it is this: "I find if you reimport off tape through an analog capture card, I have Blackmagics decklink pro, it allows you to adjust the import quality and looks much better than doing a digital transcode using compressor."

Does anyone have thoughts on this subject. I would be very appreciative for any and all input.

Thanks so much

Stephen

If the original tape is really analog then there is an advantage to an uprez straight from the tape, since the original 720x480 digitization sacrificed some information in the horizontal direction (only). Many tape systems were not analog: Digibeta, DVCAM, HDCAM, etc.

Other than with analog sources, software up-rez can, in theory, be every bit as good, although not as fast, as hardware up-rez.

Up-rez algorithms for video fall into two classes: those that work on each frame singly and those that work on more than one frame to uprez each frame.

Each frame singly.
Photoshop does this when it resamples photos. Photoshop thinks its "bicubic-smoother" algorithm does the best up-rez. It is subtley different from its "bicubic-sharper" algorithm for down-rez.
Shake recommends a Mitchell or Catmull-Rom filter (which are in the family of "cubic" filters) for up-rez (and a rather different filter for down-rez). Remember, shake was Apple software from 2002-2009.
Compressor offers three algorithms: "Nearest pixel"; "Linear filter"; "Statistical prediction". Nearest pixel produces sharp edged blocks of pixels, which is hardly an up-rez. Linear filter is a filter (convolution) as described in an article by Jason Summers. It matches his first illustration with triangle shape. Statistical prediction, despite its fancy name, seems to be another filter (convolution) very like Summers' third illustration. This is the Catmull-Rom filter*. That's about as good as up-rezzing filters get. There are additional problems concerning gamma in the application of such filters.

Multi-frame algorithms.
It is said that some wondrous up-rez solutions use multi-frame algorithms. Wherever there is slight image motion additional detail can be gleaned for each frame from neighbor frames. Also temporal noise can be separated from image.

Larry Jordan's article makes a false distinction between up-scaling and up-rezzing. Up-scaling is up-rezzing. FCP's up-rezzing happens to be particularly ugly and blurry. The filter (convolution), if this is what it is, is monstrous, resembling a triangle in the middle and Summers' fourth illustration beyond.

Dennis Couzin
Berlin, Germany

[*Note added 23 August 2003: I've verified, for complex 1-dimensional image and 2x up-rez, that it is exactly the Catmull-Rom filter.]

Thanks for the reply Dennis, much appreciated. I am a bit lost in the details here, is there a solution as simple as:

"Take your final 720x480 quicktime and run it through ______________(name of software) in order to turn the film
into a 1280x720 quicktime."

Thanks in advance,

Stephen

Stephen:
I should add that my comments were only about progressive video images. Interlaced material must be deinterlaced before uprez, and this introduces so much image quality loss (particular to the type of deinterlacing) that the question which uprez algorithm is best becomes even more difficult.

Like Larry Jordan I find Compressor can do a pretty nice uprez, but I disagree with his suggestion about which algorithm to choose. I just did a ~2x uprez test and even my old eyes could see the superiority of Compressor's "Statistical prediction" over its "Linear filter".

Dennis Couzin
Berlin, Germany