[Ffmpeg-devel] Interlaced decoding internals?

[Michael Niedermayer]

Hi

On Tue, Feb 27, 2007 at 11:45:08AM +0100, Baptiste Coudurier wrote:
> Hi
> 
> Baptiste Coudurier wrote:
> > Hi
> > 
> > Michael Niedermayer wrote:
> >> 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 
> >>
> > 
> > here it is:
> > mjpeg_top.mov, mjpeg_bottom.mov on mplayerhq.
> 
> Michael, did you have some time to check this issue ?

no sorry, far too much to do, this one is rather low priority, and i 
didnt see a clean solution for it :(

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

The worst form of inequality is to try to make unequal things equal.
-- Aristotle
-------------- 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/20070228/17b00c8e/attachment.pgp>