[opendtv] Re: Production Codecs

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Wed, 16 Jul 2008 12:44:12 -0400

At 8:20 AM -0700 7/16/08, dan.grimes@xxxxxxxx wrote:
When you say drop four frames, I assume you are talking about the time code and not actually dropping essence. Am I correct?

I wish we didn't have to deal with 29.97 and just use 30. Is there any reason to work in a non-integer format as of Feb. 19, 2009? I suppose I'll still need to work with other systems out there.

Yes. Everything will still be 59.94 in the U.S.

Not to worry though. As i mentioned earlier, virtually ALL acquisition gear supports 59.94 - some offer the ability to shoot at 60 as well.

Are there any insights you can provide to helping get MXF to work properly? Or is this something that must be worked out at the manufacturer's level? We are hiring a broadcast systems integrator so hopefully they will know and be able to work out the issues. But I would also like to know for servicing issues.

Discuss this situation with the vendors supplying your acquisition gear and the vendors supplying your production gear (i.e. Avid). They will tell you what features are supported, and what they expect to support in the future. And remember, TV happened for many decades before anyone knew what metadata was. Think of it as "potentially" useful information.; it really depends on what you are doing with it.

It seems like there would be problems treating a frame as a field. But I imagine the software deals with each differently so long as it knows which one it is working with. Mixing a progressive frame and an interlace field would need some special processing, although I am not sure what that process would be. Perhaps deinterlacing with predictive fields plus down scaling to match the 720 raster?

The field frame analogy is a bit misleading. Let's assume you are going to acquire video using 720@xxxxxxx That's all you need to worry about as long as this is your mastering format. IF you need to convert to 1080@xxxxxx, the conversion device (or software) will take a 1280 x 720 FRAME and create a 1920 x 540 field using simple scaling techniques. Going the other way is more problematic as you must de-interlace to create the progressive frame.

The 3:2 pulldown issue is also irrelevant if you are mastering in 720@xxxxxxx it only comes into play if you are shooting at 23.96p or transferring 24P film to video. OR if you are trying to emulate the film look in software by manipulating 720@xxxxx source to look like film (i.e. removing information and simulating film flicker).


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