Before this patch, the FFmpeg MXF parser correctly detects content with 
2 fields in 1 AVPacket as e.g. interlaced 720x486 but the FFmpeg JPEG 
2000 decoder reads the JPEG 2000 SIZ header without understanding that 
the indicated height is the height of 1 field only so overwrites the 
frame size info with e.g. 720x243, and also completely discards the 
second frame, which lead to the decoding of only half of the stored 
content as "progressive" 720x243 flagged interlaced.

Example file:
https://www.digitizationguidelines.gov/guidelines/MXF_sampleFiles/RDD48-sample12-gf-jpeg2000-ntsc-4.2.zip

Before this patch:
Stream #0:0: Video: jpeg2000, yuv422p10le(bottom coded first (swapped)), 
720x243, lossless, SAR 9:20 DAR 4:3, 29.97 tbr, 29.97 tbn, 29.97 tbc

After this patch:
Stream #0:0: Video: jpeg2000, yuv422p10le(bottom coded first (swapped)), 
720x486, lossless, SAR 9:10 DAR 4:3, 29.97 fps, 29.97 tbr, 29.97 tbn