[FFmpeg-devel] [PATCH] [3/??] [1/1] Libavfilter - Sws_scale filter

[Michael Niedermayer]

On Sat, Feb 16, 2008 at 12:47:43PM +0100, Vitor Sessak wrote:
> Hi
>
> This filter is needed for the filter graph infrastructure to compile.
>
> -Vitor

[...]
> static int config_props(AVFilterLink *link)
> {
>     ScaleContext *scale = link->src->priv;
>     int w, h;
> 
>     if(scale->sws)
>         sws_freeContext(scale->sws);
> 
>     w = scale->w;
>     h = scale->h;
>     if(!w)      w = link->src->inputs[0]->w;
>     if(!h)      h = link->src->inputs[0]->h;

>     if(w == -1) w = scale->h*link->src->inputs[0]->w/link->src->inputs[0]->h;
>     if(h == -1) h = scale->w*link->src->inputs[0]->h/link->src->inputs[0]->w;

w/h should be set depending in the chroma plane resolution so for example
YUV420 should end with even width&height
Id also check that the final w/h are not negative, as above can
overflow.


[...]
> static void start_frame(AVFilterLink *link, AVFilterPicRef *picref)
> {
>     AVFilterLink *out = link->dst->outputs[0];
> 
>     out->outpic      = avfilter_get_video_buffer(out, AV_PERM_WRITE);
>     out->outpic->pts = picref->pts;
> 

>     out->outpic->pixel_aspect.num = picref->pixel_aspect.num * out->h * link->w;
>     out->outpic->pixel_aspect.den = picref->pixel_aspect.den * out->w * link->h;

>     av_reduce(&out->outpic->pixel_aspect.num, &out->outpic->pixel_aspect.den,
>                out->outpic->pixel_aspect.num,  out->outpic->pixel_aspect.den,
>          FFMAX(out->outpic->pixel_aspect.num,  out->outpic->pixel_aspect.den));

This doesnt make any sense, the FFMAX will cause this to do exactly nothing.


> 
>     avfilter_start_frame(out, avfilter_ref_pic(out->outpic, ~0));
> }
> 
> 
> /* TODO: figure out the swscale API well enough to scale slice at a time */

Where is the problem with slices? I think they should be implemented soon
as they would help detecting slice related bugs in the filter system early.
Though that can be after this is applied ...


> static void end_frame(AVFilterLink *link)
> {
>     ScaleContext *scale = link->dst->priv;
> 
>     sws_scale(scale->sws, link->cur_pic->data, link->cur_pic->linesize, 0,
>               link->cur_pic->h, link->dst->outputs[0]->outpic->data,
>               link->dst->outputs[0]->outpic->linesize);
>     avfilter_draw_slice(link->dst->outputs[0], 0, link->dst->outputs[0]->h);
>     avfilter_end_frame(link->dst->outputs[0]);
> 
>     avfilter_unref_pic(link->cur_pic);
>     avfilter_unref_pic(link->dst->outputs[0]->outpic);
> }

This misses handling of interlaced frames. That is
running sws_scale twice once on even and once on odd lines. Also i think a
top field first / bottom field first / progressive variable is missing in
the filter system.
Note, yes this needs 2 sws contexts.

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

If you really think that XML is the answer, then you definitly missunderstood
the question -- Attila Kinali
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20080217/cd2d7e6a/attachment.pgp>