[Ffmpeg-devel] Interlaced decoding internals?

[Michael Niedermayer]

Hi

On Sun, Feb 11, 2007 at 01:58:12PM +0100, Baptiste Coudurier wrote:
> Baptiste Coudurier wrote:
> > Michael Niedermayer wrote:
> >> Hi
> >>
> >> On Tue, Feb 06, 2007 at 01:31:04PM +0100, Baptiste Coudurier wrote:
> >>> Michael Niedermayer wrote:
> >>>> On Tue, Feb 06, 2007 at 11:08:20AM +0100, Baptiste Coudurier wrote:
> >>>>> Hi
> >>>>>
> >>>>> Michael Niedermayer wrote:
> >>>>>> Hi
> >>>>>>
> >>>>>> On Mon, Feb 05, 2007 at 08:31:41PM +0200, Kostya wrote:
> >>>>>>> I'm working on adding interlaced frame support for VC-1 and
> >>>>>>> has some question regarding AVCodecContext internals:
> >>>>>>> What do avctx->interlaced_frame, avctx->top_field_first
> >>>>>>> and avctx->repeat_pict affect if set by decoder?
> >>>>>> they are not in AVCodecContext but AVFrame
> >>>>>> they affect display, top_field_first affects the order in which
> >>>>>> fields are shown, interlaced_frame affects if the frame is shown
> >>>>>> as frame or as 2 fields at 2 seperate times (assuming the player
> >>>>>> applictaion cares about the at all of course ...)
> >>>>> You'll laugh, what can I do if the interlaced info is in the container ?
> >>>>> I have some mjpeg a bottom field first, and info is in "fiel" atom.
> >>>>> I'll fix decoder, but I need a way to supply that info.
> >>>>> What do you prefer ? Adding a field to avctx ? 
> >>>> avctx is problematic as top-field-first can change between frames in
> >>>> MPEG so with decoder delay and multiple threads its the perfect recipe
> >>>> for troubble
> >>>> adding top-field-first to AVStream seems like the better solution,
> >>>> that way the demuxer can export it without interfering with the codec
> >>>> the same may (or may not ...) be a good idea for width/height, so
> >>>> the width and height for mpeg4/h263 in mov could be dealt with nicer
> >>>> maybe ...
> >>> So, then I need to set picture->top_field_first before passing it to the
> >>> decoder.
> >>>
> >>> Attached patch is working, but IMHO is ugly.
> >> yes this doesnt look good, i thought the container top field first was
> >> just for display if its needed for decoding then it must be passed through
> >> extradata that of course assumes that there is not enough information in
> >> the jpeg stream itself to decode it correctly (which i have some doubt about
> >> also we could choose simply not to support these jpegs)
> > 
> > I need to reread specs, AFAIK jpeg does not support interlacing,
> > mjpeg in mov/avi, specify total width/height in container, and field
> > height in bitstream.
> > 
> > I would like to support them, bottom field is almost everytime used in NTSC.
> > 
> >> also the changes to mjpeg.c contain cosmetics and ive a bad feeling about
> >> them (they arent breaking all interlaced non mov mjpeg or?)
> > 
> > Currently interlacing is detected by checking bitstream height against
> > height set before decoding (from container) and then assume interlaced
> > content and always use top field first (which is wrong IMHO)
> > 
> > I'll use mov "fiel" atom then, buf if someone store bottom field first
> > in avi... who knows.
> > 
> 
> Ping ?

upload sample videos with top and botom field first 

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

I have often repented speaking, but never of holding my tongue.
-- Xenocrates
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: not available
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20070211/5422e37f/attachment.pgp>