[FFmpeg-devel] [PATCH] add top video filter

[Michael Niedermayer]

On Mon, Mar 28, 2011 at 08:35:19PM +0100, Mark Himsley wrote:
> On 28/03/2011 19:39, Michael Niedermayer wrote:
> > On Mon, Mar 28, 2011 at 02:47:20PM +0100, Mark Himsley wrote:
> >> Dear developers,
> >>
> >> Converting to and from interlaced PAL DV files, with their  
> >> bottom-field-first interlace field order, can be a pain. Converting tff  
> >> files to DV results in tff DV files, which are hard to work with in  
> >> editing software.
> >>
> >> The attached filter can:
> >>
> >> Convert field order by either moving all of the lines in the picture up  
> >> by 1 line (bff to tff conversion) or down by 1 line (tff to bff  
> >> conversion). The remaining line, the bottom line in bff to tff  
> >> transforms or the top line in tff to bff transforms, is filled by  
> >> copying the closest line in that field.
> >>
> >> Previous to this filter I have used a filter chain like this to do bff  
> >> to tff conversion.
> >>
> >> format=yuv422p,crop=720:575:0:1,pad=720:576:0:0:black
> >>
> >> but that chain does not fill the remaining line.
> >>
> >> -- 
> >> Mark
> > 
> >>  doc/filters.texi         |   29 +++++++
> >>  libavfilter/Makefile     |    1 
> >>  libavfilter/allfilters.c |    1 
> >>  libavfilter/vf_top.c     |  184 +++++++++++++++++++++++++++++++++++++++++++++++
> > 
> > i think vshift or vmove or something like that is a better name
> 
> I chose the filter name 'top' to match the -top command. I'm not keen on
> vshift or vmove because, in my mind, they don't describe the purpose of
> the filter - to change between top and bottom field first.
> 
> But it's only a name, so it's not something I'm going to stress about :-)

same here i dont mind the name, but ill send the users to you if they
are confused :)


> 
> > off topic a bit:
> > also theres another way to convert between top & bottom field first
> > and that is to combine 2 fields from 2 seperate frames
> 
> Yes indeed. Removing the very first field and the very last field from a
> clip will also swap the fields of the whole clip. But the down sides are
> that you've lost a whole frame off the clip's duration and, more
> importantly, video cuts which were on frame boundaries are now in the
> middle of frames - making re-editing much more difficult.
> 
> Back on topic...
> 
> > [...]
> >> +static int query_formats(AVFilterContext *ctx)
> >> +{
> >> +    enum PixelFormat pix_fmts[] = {
> >> +        PIX_FMT_YUV444P,  PIX_FMT_YUV422P,
> >> +        PIX_FMT_YUVJ444P, PIX_FMT_YUVJ422P,
> >> +        PIX_FMT_RGB24,    PIX_FMT_BGR24,
> >> +        PIX_FMT_ARGB,     PIX_FMT_ABGR,
> >> +        PIX_FMT_RGBA,     PIX_FMT_BGRA,
> >> +        PIX_FMT_NONE
> >> +    };
> > 
> > i think the filter could easily be made to support more formats
> 
> It won't currently support formats with half-vertical resolution chroma.
> I think it's beyond my mathematical capabilities to move that chroma up
> of down by half a line.
> 
> Or perhaps this filter should leave the half-vertical resolution chroma
> where it is... I think some experiments need to be done with chroma-key
> recorded on DV and converted to IMX-30, for instance.
>

> But, yes, you're right that this might not be a complete list of formats
> that can be supported by this filter.

yes, thats what ive meant, there is 15/16/48 bit rgb at least missing

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

Everything should be made as simple as possible, but not simpler.
-- Albert Einstein
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