[Ffmpeg-devel] interlace field order
Dieter
freebsd
Mon Feb 20 18:53:22 CET 2006
After googling a bit, I find that:
Mpeg can be either top-field-first or bottom-field-first.
DV is always bottom-field first.
When converting mpeg to DV, ffmpeg sometimes outputs the wrong
field order.
So the question is: how can we detirmine when the field order needs
to be corrected?
In libavcodec/mpeg12.c mpeg_decode_picture_coding_extension()
I turned on the printf for top_field_first. Some files have
top_field_first all 0, some have it all 1, and some have
*interesting* changes, like being 1 for awhile, then changing
to an alternating pattern, with 1, 2 and 3 samples:
top field first=1
top field first=1
top field first=1
top field first=1
top field first=1
top field first=1
top field first=1
top field first=1
top field first=1
top field first=1
top field first=0
top field first=0
top field first=0
top field first=1
top field first=0
top field first=0
top field first=1
top field first=1
top field first=1
top field first=0
top field first=1
top field first=1
top field first=0
top field first=0
top field first=0
I have trouble believing that the field order is supposed to be
changing this frequently.
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