[Ardour-Dev] Ardour Timecode

John Emmas johne53 at tiscali.co.uk
Thu Nov 1 15:19:00 PDT 2012

I'm not sure if this comment from Reuben is stipulated in a specification somewhere but it makes some sense....

On 31 Oct 2012, at 05:04, Reuben Martin wrote:

> Most editors lock to the DF timing. But then 
> after the content is rendered and played out for broadcast, it's played out at 
> the 30/1.001 rate.

Consider that an error of 3.6mS per hour would accumulate to an error of 1 whole frame every 9.25 hours or so.  Therefore you'd expect that to be correctable in the dropframe specification.  But it isn't AFAIK.

Which suggests that for the purposes of production, editing and number calculation, 29.97 is assumed to be the actual frame rate (precisely, not approximately).  Only when the picture actually gets transmitted does the rate become slightly faster, at (30 *1000 / 1001).

That makes considerable sense - as well as implying that Avid's 2997/100 frame rate is correct - at least as far as the _calculated_ timecode values are concerned.  Interesting....


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