[Ffmpeg-devel] [PATCH] remove drop timecode flag

Trent Piepho xyzzy
Sun Apr 15 20:30:13 CEST 2007

On Sun, 15 Apr 2007, Rich Felker wrote:
> On Sun, Apr 15, 2007 at 10:49:17AM -0700, Trent Piepho wrote:
> > 107892 == 0x1a574 == 00:59:56:12, it's all the same, just an integer
> > written in different formats.
> These are not equal. 107892 is either 00:59:56:29 or 01:00:00:00,
> assuming 30000/1001 fps. A non-broken program should be using the
> correct pts not this SMPTE bullshit.

I think there is a misunderstanding about what timecode is for.  It has
nothing to due with playback speed or dropping frames or synchronizing
audio and video during playback.  It is not a replacement for PTS.

It is just a frame ID for each frame.  Back in the days of analog tape,
people wanted an ID for each frame, since how else could you edit your
tapes?  If I find the frame I want to edit on with my VTR, how will I never
find that frame again if it has no ID?  Measure the tape with a ruler?

So they embedded an ID, called a timecode, into the VBI.  And equipment
today still wants this same data, just now we embed the BCD values as a few
digital bytes in our digital files instead of pulses in the VBI.

107892 converted to base 30/base 60 is '00:59:56:12'.

107892 % 30 = 12
(107892/30) % 60 = 56
(107892/30/60) % 60 = 59

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