[FFmpeg-devel] [RFC] interlace flagging and detecting.

Michael Niedermayer michaelni at gmx.at
Tue Oct 9 23:26:07 CEST 2012

On Tue, Oct 09, 2012 at 03:52:50PM +0100, Tim Nicholson wrote:
> I am trying to tie up some loose ends in the interlace flagging within
> ffmpeg brought to light by attempting to sort out the missing, but
> mandatory 'fiel' atom in uncompressed quicktimes.
> I could do with some confirmation from those more familiar that I am on
> the right track.
> From what I have gleaned by poring over the code, ffmpeg and libraries
> principally use the AVFrame struct 'interlaced_frame' and
> 'top_field_first' flags, although there is also AVCodecContext's
> field_order enum which seems to exist in order to cover the flag
> permutations required by the qt fiel atom. AFAIK currently these two are
> completely independent. I can find no code to link them or use one if
> the other is blank.

> For example, a sample uncompressed 2vuy .mov when inspected by 'ffprobe
> -show_frames' has interlaced_frame and top_field_first = 0 whilst the
> 'fiel' atom indicates interlaced/bottom field first.

thats a bug, the decoder should read the field_order from the context
and fill it in the AVFrames it returns

> I notice also that although many codecs seems to access the AVFrame
> 'interlaced_frame' for making decisions about interlace handling the


> Avid Meridien coder (avuienc.c) specifically uses AVCodecContext's
> field_order, so there does seem to be some inconsistency.

are there other raw encoders that need interlaced info at init time ?
if not then its not really inconsistent.
non raw encoders take the interlaced info from user specified
parameters normally ...

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If you think the mosad wants you dead since a long time then you are either
wrong or dead since a long time.
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