[FFmpeg-devel] [PATCH] Implement PAFF in H.264

[Jeff Downs]

On Mon, 8 Oct 2007, Michael Niedermayer wrote:

> On Thu, Oct 04, 2007 at 03:07:09PM -0400, Jeff Downs wrote:

[...]

> > 8. paff-picmgmt.patch
> > Manage Picture buffers for fields as well as frames. Pair complementary 
> > fields into one MPV Picture.  Part of PAFF implementation.
> > 

[...]

> > @@ -3991,8 +3998,50 @@
> >      }
> >  
> >      if(h0->current_slice == 0){
> > -        if(frame_start(h) < 0)
> > +        /* See if we have a decoded first field looking for a pair... */
> > +        if (s0->first_field) {
> > +            assert(s0->current_picture_ptr);
> > +            assert(s0->current_picture_ptr->data[0]);
> > +            assert(s0->current_picture_ptr->reference != DELAYED_PIC_REF);
> > +
> > +            /* figure out if we have a complementary field pair */
> > +            if (!FIELD_PICTURE || s->picture_structure == last_pic_structure) {
> > +                /*
> > +                 * Previous field is unmatched. Don't display it, but let it
> > +                 * remain for reference if marked as such.
> > +                 */
> > +                s0->current_picture_ptr = NULL;
> > +                s0->first_field = FIELD_PICTURE;
> 
> first field is set to 0, 1, FIELD_PICTURE and tested against 0/not 0
> this is inconsistent
> also it should be here !=0 already

Hmm not sure I follow your comment.  This block is dealing with any sort 
of unmatched field pair. That is,

Had an initial (unmatched as of yet) field.
Now decoding either a frame picture (!FIELD_PICTURE) or a field of same 
parity.

FIELD_PICTURE is 0/1. If desired for clarity, it can easily be changed to: 

first_field = FIELD_PICTURE ? 1 : 0

or

if (!FIELD_PICTURE) 
first_field = 0


	-Jeff