[FFmpeg-devel] [PATCH] ffmpeg: fix setting field_order during muxing

[Jerome Martinez]

Le 10/08/2017 à 04:43, James Almer a écrit :
> AVFrame.top_field_first doxy states
>
> "If the content is interlaced, is top field displayed first."
>
> And AVFieldOrder doxy defines:
>      AV_FIELD_TB,          //< Top coded first, bottom displayed first
>      AV_FIELD_BT,          //< Bottom coded first, top displayed first
>
> Fixes ticket #6577

IMHO the subject is complex, and everyone should be in sync with the 
purpose of each mux_par->field_order value and understand impact on 
other players (sometimes the MOV metadata is the only one available as 
the codec has no info e.g. uncompressed or jp2k) before changing current 
behavior in a so general manner.
What I understood is that it is based on QuickTime specs (the mapping is 
1 to 1 from fiel atom) and TN2162 and that they are not easy to 
understand and maybe misleading : the feedback I got in the last years 
about the meaning of this atom are not really in sync with specs having 
stored vs displayed, and such change may have an impact on how other 
players handle fiel atom or other metadata in the way it is currently 
implemented by FFmpeg.