[FFmpeg-devel] [PATCH] Change default behaviour of scale filter from 'progressive' to 'auto'

Michael Niedermayer michaelni at gmx.at
Tue May 1 10:26:39 CEST 2012

On Tue, May 01, 2012 at 08:29:47AM +0100, Tim Nicholson wrote:
> On 30/04/12 14:44, Michael Niedermayer wrote:
> > On Tue, Apr 17, 2012 at 10:15:15AM +0100, Tim Nicholson wrote:
> > I think the patch is correct but until the input interlace flag is
> > ALOT more reliable i dont think we should apply this as it likely
> > would worsen the overall results for the end user, who after this
> > patch would need to manually override it for all files while now
> > only interlaced files need a override to be sure they are scaled
> > correctly
> > 
> Fair comment. One of the problems with the current system is that in
> order to perform the override, one has to construct a command string,
> run a test on the material. Observe where scale filters ma be auto
> inserted. Then reconstruct the command line with a full -vf string and
> manually inserting the scaler with interlace turned on, or preceded by a
> setfield filter. This can be tedious and simple command strings end up
> being turned into more complex lines with filterchains. Using just -vf
> setfield=prog|tff|bff on its own doesn't seem to work.
> I therefore wonder if a better solution at this stage would be to add an
> additional SWScaler AVOption to enable selecting the default mode.
> Current users would see no change, and those who need it could simply
> add the option to their command line and get the results they need in a
> more elegant and simple manner than described previously.
> I will try and bone up on the SWScaler API and see what it would take to
> achieve that if you think that approach might work.

I think adding more possibly values to the interlace field used in
libavfilter is better. Its not certain the interlace state is the
same in the whole filter graph, also other filters may similarly
need to accurately know the interlacing/progressive state

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Avoid a single point of failure, be that a person or equipment.
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