[FFmpeg-trac] #3147(avcodec:new): H264 - Wrong field order

FFmpeg trac at avcodec.org
Wed May 7 11:36:53 CEST 2014

#3147: H264 - Wrong field order
             Reporter:  Underground78  |                    Owner:
                 Type:  defect         |                   Status:  new
             Priority:  normal         |                Component:  avcodec
              Version:  git-master     |               Resolution:
             Keywords:  h264           |               Blocked By:
             Blocking:                 |  Reproduced by developer:  0
Analyzed by developer:  0              |

Comment (by t.rapp):

 I also stumbled over this problem a few weeks ago. From looking at the
 source and some small debugging it seems that MediaInfo derives the field
 order from the picture "bottom_field_flag":

  Recommendation H.264
 page 80:

  bottom_field_flag equal to 1 specifies that the slice is part of a coded
  bottom field. bottom_field_flag equal to 0 specifies that the picture is
  coded top field. When this syntax element is not present for the current
  slice, it shall be inferred to be equal to 0.

 FFmpeg relies only on the information in `h->sei_pic_struct`. When trying
 to use `h->picture_structure` I stumble over the issue that FFmpeg
 defaults to `h->picture_structure = PICT_FRAME` when the bottom_field_flag
 is absent instead of `h->picture_structure = PICT_BOTTOM_FIELD` as
 mentioned in the specs. But then I am unsure how to differ between
 interlaced and non-interlaced data.

Ticket URL: <https://trac.ffmpeg.org/ticket/3147#comment:3>
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