The Submission Process

But direct conversion from 23-, 24- or 25-frame formats to 29 or 30 frames produces artifacts that aren’t acceptable to viewers from any area, and motion-predictive frame-rate conversion is time-consuming and may still produce visible artifacts on some material. Conversion to 59 or 60 frames per second would be desirable to accommodate all formats best, but 1080P/60 output isn’t currently an available live production option. All of these considerations led to a decision to use 1080i/29.97 (59.94 field images per second) with stereo 48 KHz audio as the production standard.

All 29.97-frame clips translated directly, with only scaling of each field or frame to get to the output format.
Thirty-frame clips were conformed down to 29.97 in Apple Cinema Tools, with audio rate conversion to 48 KHz using Apple Compressor.

Twenty-four-frame clips were conformed to 23.98, again using Cinema Tools and Compressor, and the 23.98-frame video clips were pulled up to 29.97 with a standard U.S. 2:3 pull-up, as is done in telecine transfers.

Twenty-five-frame clips were also conformed to 23.98 using Cinema Tools and Compressor, but the 4% change in pitch resulting from the speed change from 25 to approximately 24 frames per second is significant and may be a problem. Because of the short nature of the 20-second clips, our evaluation indicated that the changes didn’t warrant the use of pitch-shift processing on each clip to maintain the original pitch. For longer clips or full programs, pitch can be important, and there’s good-quality software now that can provide pitch shifting when speed changes are required. Care must be taken not to introduce channel-phasing errors that might be decoded by stereo synthesizers or surround-sound decoders into sound position errors in surround-equipped viewing environments.

The results were laid onto a continuous, 1080i/29.97 Final Cut Pro timeline using the Apple ProRes codec. Program title and producer credits were added to each clip, and sponsor and category graphics were inserted between the groups of finalist clips in each category. The entire timeline then was rendered for real-time playback. The use of a timeline for playback instead of a tape or disk solution allowed continual manual update of program timing to accommodate the show Master of Ceremonies and award presenters.

Based on the comments from the attendees, the visual effects of the conversions were certainly acceptable. Program playbacks might require different techniques to maintain sufficient quality across formats, but based on the quality of some of the conversions that I received from the producers, my approach would give better results for many of the programs, at least for North American audiences, where 2:3 pull-up is an acceptable form of film-to-video conversion.

As in all video-processing applications, careful evaluation of the results, with consideration of the final display conditions, is a big part of deciding how to proceed. The conversion and display tools are continually changing, and in two years, my report most certainly will be different.

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