[FFmpeg-devel] H.264 + PAFF: BBC HD recording shows extreme interlacing artefacts

Michael Niedermayer michaelni
Thu Nov 1 15:46:39 CET 2007

On Thu, Nov 01, 2007 at 02:51:03PM +0100, Reinhard Nissl wrote:
> Hi,
> Michael Niedermayer schrieb:
> >> Another question that arises after colorspace conversion is displaying
> >> or deinterlacing the fields in correct order. I was relying on
> >> top_field_first but it seems that it is always zero as I cannot find any
> >> reference of this frame member in h264.c. As mpeg12.c references this
> >> member in mpeg_decode_picture_coding_extension() I assume that filling
> >> this member is still missing in h264.c.
> >>
> >> The attached patch tries to address this issue. I hope it is correct.
> > 
> > i dont think this patch is sufficient to set top_field_first correctly
> > i think it will be still wrong (=0) for all MBAFF
> Well, I had a look into the spec and into h264.c and cannot find any
> other variable which explicitly tells me "bottom_field_first" than
> picture_structure.

maybe field_poc could be used,i dunno if this is how its supposed to be
detected though

> I think you address the case where MbaffFrameFlag == 1 i. e. when
> mb_adaptive_frame_field_flag == 1 && field_pic_flag == 0. In that case
> top_field_first will be 1 due to picture_structure != PICT_BOTTOM_FIELD.
> I don't know, how you came to the conclusion, that top_field_first will
> be 0 in such a case.

yes, i was wrong, it will always be 1 but this doesnt change anything its
wrong either way


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The worst form of inequality is to try to make unequal things equal.
-- Aristotle
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