[FFmpeg-devel] [PATCH 3/4] Add setpts filter by Victor Paesa.

[Michael Niedermayer]

On Thu, Jun 17, 2010 at 12:48:37AM +0200, Stefano Sabatini wrote:
> On date Wednesday 2010-06-09 03:39:04 +0200, Michael Niedermayer encoded:
> > On Wed, Jun 09, 2010 at 12:17:35AM +0200, Stefano Sabatini wrote:
> > > ---
> > >  doc/libavfilter.texi     |   46 +++++++++++++++++
> > >  libavfilter/Makefile     |    1 +
> > >  libavfilter/allfilters.c |    1 +
> > >  libavfilter/vf_setpts.c  |  127 ++++++++++++++++++++++++++++++++++++++++++++++
> > >  4 files changed, 175 insertions(+), 0 deletions(-)
> > >  create mode 100644 libavfilter/vf_setpts.c
> > > 
> > > diff --git a/doc/libavfilter.texi b/doc/libavfilter.texi
> > > index 1de27d9..cf53a93 100644
> > > --- a/doc/libavfilter.texi
> > > +++ b/doc/libavfilter.texi
> > > @@ -237,6 +237,52 @@ ratio of the input image.
> > >  
> > >  The default value of @var{width} and @var{height} is 0.
> > >  
> > > + at section setpts
> > > +
> > > +Change the PTS (presentation timestamp) of the input video frames.
> > > +
> > > +Accepts in input an expression evaluated through the eval API, which
> > > +can contain the following constants:
> > > +
> > > + at table
> > > + at item PTS
> > > +the presentation timestamp in input
> > > +
> > > + at item PI
> > > +Greek PI
> > > +
> > > + at item E
> > > +Euler number
> > > +
> > > + at item AVTB
> > > +the FFmpeg Time Base
> > > +
> > > + at item N
> > > +the count of the input frame, starting from 0.
> > > +
> > > + at item STARTPTS
> > > +the PTS of the first video frame
> > > + at end table
> > 
> > missing:
> 
> > average fps
> 
> computed in which interval?

in the one available
a demuxer with index might even set it exactly


> 
> > interlace flag
> > file position
> 
> > timebase
> 
> which timebase? As far as I know the timebase in the filterchain is
> fixed, and is AV_TIME_BASE.
> 
> > guessed real minimal timebase
> 
> please suggest an algorithm for computing it if you have already an
> idea

Avfilterwhatever.* = AVStream.*


> 
> > previous input pts
> > previous output pts
> 
> I added them in a previous version, but then I didn't know how to deal
> with them for the first frame. I suppose they may be set to 0 or
> AV_NOPTS_VALUE, but then I need to understand how can I deal with
> them, for example in the expression: outpts=prev_outpts+XXX.

prev= curr - 1/avg_fps


>  
> > obviously some of these could be usefull
> 
> Also I suggest to add the more complex features in successive patches,
> this is a port afterall.

thats ok but timebase availablity in the filterchain and fixing timestamps
in ffplay is related

[...9
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

it is not once nor twice but times without number that the same ideas make
their appearance in the world. -- Aristotle
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