How does PMS determine if a video is interlaced or progressive?

Plex Media Server
1

I am noticing interlacing artefacts playing back UK TV DVR files, these files are typically 1080i but Plex thinks they are progressive, so I get no deinterlacing…

Mediainfo correctly identifies them, eg:


Video
ID                                       : 256 (0x100)
Menu ID                                  : 1 (0x1)
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L4
Format settings                          : CABAC / 4 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 4 frames
Codec ID                                 : 27
Duration                                 : 1 h 29 min
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 25.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : MBAFF
Scan type, store method                  : Interleaved fields
Scan order                               : Top Field First
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709

Yet after doing an alayze on the file Plex reports:
image

So, what method does PMS use to determine progressive or interlaced please (ffprobe) ?

2

Never mind, looking at the logs it appears to use ffmpeg and looks at around the first 100 frames