[Ffmpeg-devel] [PATCH] remove drop timecode flag
Mon Apr 16 03:00:32 CEST 2007
On Sun, Apr 15, 2007 at 03:58:30PM -0700, Trent Piepho wrote:
> > also what exactly is the problem with just setting the true sec/min/hour
> > and frame within that second as mandated by mpeg4 in the mpeg2 case too
> > if its really just an abstract ID?
> I'm not sure what you mean by "frame within that second".
> In your method, what is the formula for the timecode values for frame i at
> Do you mean:
> double t = i * 1001 / 30000;
> int hours = (int)(t/3600) % 60;
> int mins = (int)(t/60) % 60;
> int secs = (int)(t) % 60;
> int frame = (t - (int)t)*30000.0/1001.0 + 0.5;
yes minus the floats and rounding
> This has two problems. One, it doesn't follow the SMPTE spec. Frame
> 510 should have frame id '00:00:17;00', but this method gives it
> frame id '00:00:17;01'
> This makes a difference! How many frames are there between '00:00:16;00'
> and '00:00:17;10'?
you dont know that due to frame/field repetition
> In SMPTE timecode, there are exactly 40 frames. In
> this alternate timecode, there are a 39 frames. The interval is different
> because it's not following the SMPTE spec. It's not following the MPEG-2
> spec either.
NOTE - The information carried by time_code plays no part in the
so IMHO no matter what you set it to the file is still valid mpeg2
> This alternate timecode also will use frame fields that go to :30, instead
> of always wrapping at :29.
this is caused by the rounding, i think without it 29 is max
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Those who are too smart to engage in politics are punished by being
governed by those who are dumber. -- Plato
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