[Libav-user] Reading field by field of an interlaced video

[Sampath Subasinghe]

Hi All,
     I want to estimate the motion between two fields of an interlaced 
video. Currently I run a loop of av_read_frame() and 
avcodec_decode_video2() to read the video. But I guess that when 
avcodec_decode_video2() finishes reading a frame, it must have been 
de-interlaced the two fields of a frame to the complete frame.

I have no idea how I can read field by field of the video. Please give 
me some pointers to start with.

thanks in advance.
-Sampath