[opendtv] Re: Production Codecs

  • From: dan.grimes@xxxxxxxx
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Wed, 16 Jul 2008 08:20:26 -0700

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.

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.

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?


"Richard C. Ramsden" <ramsden@xxxxxxxxxxx> 
Sent by: opendtv-bounce@xxxxxxxxxxxxx
07/15/2008 11:29 PM
Please respond to


[opendtv] Re: Production Codecs

There is a hidden standard for dealing with 720p@xxxxx
It's exactly the same as 29.97.  29.97 is 59.94 fields/sec.  Treat each 
progressive frame as an interlaced field.  Drop 4 frames where in 29.97 
you'd drop 4 fields.  This method is used in all Harris (my employer) 
equipment.  It's obvious, it works, and it doesn't break when you down 

For 23.98, I expect that some application of 3:2 pull down can resolve 
how drop frame can be applied.

SMPTE specs aren't very good these days.  There's more that's not there, 
or vaguely spec'd than that is well defined.  MXF is a nightmare.  What 
actually works is an agreement by the major players on what the spec 
means to them.


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