[Ffmpeg-devel] Interlaced decoding internals?

Michael Niedermayer michaelni
Tue Feb 6 11:28:03 CET 2007


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 ...

> (and we could get rid of
> the -top option in ffmpeg)

no, -top is needed if the info in the container+codec is wrong

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If you really think that XML is the answer, then you definitly missunderstood
the question -- Attila Kinali
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