I have been using the MP2/H264 decoders in the UMC library to perform decoded image analysis. I recently discovered that the UMC::VideoData.m_picStructure element always seems to be set to PS_FRAME even when the video is interlaced. I was under the impression that PS_FRAME should only happen for progressive video, and that interlaced frames would be either PS_TOP_FIELD_FIRST or PS_BOTTOM_FIELD_FIRST. Is this correct? Is there some other way I can determine if the video is interlaced/progressive, and if it is interlaced, which field is first?