RE: MTC and Time Code Types

• Subject: RE: MTC and Time Code Types
• From: "Cianflone, Chris" <email@hidden>
• Date: Sun, 6 Feb 2005 00:07:13 -0600
• Delivered-to: email@hidden
• Delivered-to: email@hidden
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• Thread-topic: MTC and Time Code Types

<<
30 versus 29.97 is the actual rate (fps, naturally).

Drop versus not is the counting method (i.e. how an actual frame number
is converted to hh:mm:ss:ff).
>>

That's what I was hoping and that is a nice explanation.  I think I am getting more tripped up on what various sources are calling the various "frame rates" and "counting methods".  For example, in my original e-mail I mentioned the MIDI Spec referring to the following:

>      0 = 24 fps
>      1 = 25 fps
>      2 = 30 fps (Drop Frame)
>      3 = 30 fps (Non-Drop Frame)

So if I am understanding this all correctly, shouldn't this simply be listed as

0 = 24 fps
1 = 25 fps
2 = 29.97 fps
3 = 30 fps

without any regard to drop/non-drop?

And then I tried a quick experiment in Digital Performer which lists the following SMPTE formats:

24 fps
25 fps
29.97 fps Drop
29.97 fps Non-Drop
30 fps

However, if I snoop on what MIDI data is getting sent in the above cases, it looks like this when shuttling to time 0:

24 fps :                           F0 7F 7F 01 01 00 00 00  00 F7, so 00 = "0 = 24 fps"
25 fps :                           F0 7F 7F 01 01 20 00 00  00 F7, so 20 = "1 = 25 fps"
29.97 fps Drop :           F0 7F 7F 01 01 40 00 00  00 F7, so 40 = "2 = 30 fps (Drop Frame)"
29.97 fps Non-Drop :  F0 7F 7F 01 01 60 00 00  00 F7, so 60 = "3 = 30 fps (Non-Drop Frame)"
30 fps :                           F0 7F 7F 01 01 60 00 00  00 F7, so 60 = "3 = 30 fps (Non-Drop Frame)"

So in the above, is the 4th line (29.97 fps Non-Drop) really supposed to be 30 fps Non-Drop?  What am I missing here?

And sorry for the late reply.  I got "dropped" by the flu late last week and am playing catch up on everything.

Thanks,
Chris


-----Original Message-----
From:   kelly jacklin [mailto:email@hidden]
Sent:   Thu 1/27/2005 9:25 AM
To:     Cianflone, Chris
Cc:     email@hidden
Subject:        Re: MTC and Time Code Types

On Jan 26, 2005, at 7:10 PM, Cianflone, Chris wrote:

>  So, what is kSMPTETimeType2997 and kSMPTETimeType2997Drop?  I have
> been searching the web all day and not really finding a sufficient
> answer to this (although a few things I found made reference to these
> extra formats).  Is there a more up-to-date MTC spec I should be
> reading?

30 versus 29.97 is the actual rate (fps, naturally).

Drop versus not is the counting method (i.e. how an actual frame number
is converted to hh:mm:ss:ff).

kelly

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