[FFmpeg-user] Missing "fiel" Video Sample Description extension in .mov's

[Tim Nicholson]

If I have an uncompressed uyvy422 mov that I stream copy to some other
file, say with:-

ffmpeg -i -c copy out.mov

Then the "fiel" extension containing the interlace information is copied
through to the output file.

However if I perform:-

ffmpeg -i in.mov -c:v rawvideo -pix_fmt uyvy422 -vtag 2vuy  out.mov

The "fiel" extension is not carried through to the output file, causing
some applications to believe the material is progressive by default.

This is a bug as the "fiel" data is mandatory for uncompressed formats.
(qtff.pdf 2012-08-14 table 4-2 p 158)

>From a perusal of the code in mov.c this is extracted to
st->codec->field_order with an AV_LOG_ERROR for unknown values
(AV_FIELD_UNKNOWN).

Since I am not seeing that error I presume it is being successfully
retrieved.

However in movenc.c the "fiel" extension is written provided that:-

track->enc->field_order != AV_FIELD_UNKNOWN

and since it is not being written I must assume that the above test is true.

It would therefore seem that track->enc->field_order is not being set
from st->codec->field_order except in the case of a stream copy.

So far I have been unable to pin down where this is/isn't happening, can
anyone with a better understanding of the mov muxer/ibavcodec help point
me in the right direction?
-- 
Tim