[Ffmpeg-devel] Re: [PATCH] mov fix fps detection

Uoti Urpala uoti.urpala
Tue Aug 8 03:30:38 CEST 2006

On Tue, 2006-08-08 at 03:01 +0200, Baptiste Coudurier wrote:
> Uoti Urpala wrote:
> > On Tue, 2006-08-08 at 00:26 +0200, Baptiste Coudurier wrote:
> >> Quoting from ISO 14496-12:
> > 
> >> stream may be the same. Great care must
> >> be taken when adding samples to a stream, that the sample that was
> >> previously last may need to have a non-
> >> zero duration established, in order to observe this rule. If the
> >> duration of the last sample is indeterminate, use
> >> an arbitrary small value and a `dwell' edit."
> > 
> > 
> >> +        /* ISO 14496-12 8.15, workaround since last entry may have an 'abritraty small value' */
> > The quote isn't talking about setting the last entry in a stream. It's
> > about handling samples which will NOT be last any more because new
> > samples are added.
> Well you are only interpreting the last sentence in the "adding new
> samples" context.

And what other context would it have?

> Last sentence may explains in general that last sample duration may have
> an 'abritraty value' or be 0 if duration is indeteminate.

No it doesn't. The last sentence is strictly about adding samples: if
the duration of the sample which _was_ last (and _is not_ last in the
resulting file) was 0, you need give it an "arbitrary small value" which
is _not_ 0. Thus your quote in the patch is wrong and misrepresents the
spec. The spec only uses the words "arbitrary small value" when talking
about samples that will _not_ be the last sample in the resulting
modified file.

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