Re: [FFmpeg-devel] [PATCH] avcodec/jpeg2000dec: support of 2 fields in 1 AVPacket

["Tomas Härdin" <git@haerdin.se>]

mån 2024-02-19 klockan 12:05 +0100 skrev Tomas Härdin:
> mån 2024-02-19 klockan 00:43 +0100 skrev Marton Balint:
> > 
> > 
> > On Fri, 16 Feb 2024, Anton Khirnov wrote:
> > 
> > > Quoting Tomas Härdin (2024-02-03 20:58:20)
> > > > I think people with knowledge how interlacing is handled in
> > > > other
> > > > formats and codecs might want to chime in.
> > > 
> > > For MPEG codecs our decoders always output (properly signalled)
> > > interlaced content as two interleaved fields in a single AVFrame
> > > flagged
> > > with AV_FRAME_FLAG_INTERLACED. Its height is the height of the
> > > whole
> > > frame, so double the number of lines in each field.
> > > 
> > > So IIUC this patch is taking the correct approach.
> > 
> > I believe interlaced HEVC has the same issue, the decoder generates
> > field 
> > pictures and not frames. Would changing the HEVC decoder be
> > acceptable to 
> > generate frames with interleaved fields?
> 
> This isn't a J2K thing, but an MXF thing. The same issue will arise
> for
> MJPEG and raw video in MXF using SEPARATE_FIELDS.

To make things worse, encoding SEPARATE_FIELDS using progressive
H.263/4/5/6 in MXF is almost certainly legal. Lawful evil.

/Tomas
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