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

[Michael Niedermayer]

Hi

On Tue, Sep 25, 2007 at 03:51:11PM -0400, Jeff Downs wrote:
> On Mon, 24 Sep 2007, Jeff Downs wrote:
> 
> > On Mon, 24 Sep 2007, Michael Niedermayer wrote:
> > > 
> > > IMHO the AVFrame.reference code should be fixed first unless this turns
> > > out to be very complex to fix
> > >
> > 
> > OK.  I took a second look at how Picture.reference is used in mpegvideo.c 
> > and h264.c.  For current SVN (no PAFF), its not too difficult to fix 
> > (replace use of reference = 1 with 4 as suggested).
> > 
> > 
> > When PAFF is considered, two problems present:
> > 
> > First, a place to store a second field's "is a reference" flag is needed, 
> > separate from the reference marking of the first field in a pair.
> > 
> > Would using s->dropable for this be an acceptable solution? Or should 
> > I continue with current_picture.reference?
> > 
> > This way:
> > 
> > s->dropable == current field or frame needs reference marking when 
> > complete.
> > 
> > current_picture.(_ptr->)reference == PICT_XXX, or 4, as dictated by 
> > and set in reference picture marking process and delayed picture holding.
> > 
> > 
> > Second, MPV_frame_start forces a value of 3 onto reference for ref frames. 
> > This could be solved by replacing "3" with s->picture_structure. But that 
> > doesn't really make complete sense for mpeg2.
> > 
> > Another option is to let MPV_frame_start still set 3, but override in 
> > h264 with picture_structure.
> > 
> > Another option still is to override with zero, and then let the frame end 
> > processing (ref marking and pic output) take total control of the 
> > reference variable handling. This is good because it isolates reference 
> > handling to one area.
> > 
> 
> Attached is a patch that cleans up handling of Picture.reference in h264 
> using some of the above-described approach.
> 
> I decided to change MPV_frame_start to use s->picture_structure for 
> reference in h264 case because it was already testing for h264 there 
> anyway. This prepares for PAFF implementation.
> 
> This also makes current_picture.reference necessarily == 
> current_picture_ptr->reference and updates any tests of either to have 
> field references in mind.
> 
> If ok, I will update PAFF implementation based on this.

ok

[...]

> +/*
> + * Value of Picture.reference when Picture is not a reference picture, but
> + * is held for delayed output.
> + */
> +#define DELAYED_PIC_REF 4

not doxygen compatible

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

I have often repented speaking, but never of holding my tongue.
-- Xenocrates
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