Error playing interlaced VC-1 content (SNB)

[9p6]

Hi. I'm getting the following error when playing an interlaced VC-1 content (from Blu-ray)

$ mpv vc1-interlaced.mkv 
 (+) Video --vid=1 (vc1 1920x1080 29.970fps)
 (+) Audio --aid=1 --alang=eng (*) 'Stereo' (ac3 2ch 48000Hz)
File tags:
 Title: O Lucky Malcolm!
mpv: gen6_mfd.c:1462: gen6_mfd_vc1_pic_state: Assertion `0' failed.

gen6_mfd.c

    if (pic_param->sequence_fields.bits.interlace == 1 &&
        pic_param->picture_fields.bits.frame_coding_mode != 0) { /* frame-interlace or field-interlace */
        /* FIXME: calculate reference field picture polarity */
        assert(0);
        ref_field_pic_polarity = 0;
    }

Ok so obviously the code for that hasn't been written but what is frame_coding_mode exactly? Is there particular type of interlaced content that is supported?

File information

General
Complete name                            : vc1-interlaced.mp4
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom (isom/iso2/mp41)
File size                                : 60.0 KiB
Duration                                 : 1 s 1 ms
Overall bit rate                         : 491 kb/s
Movie name                               : O Lucky Malcolm!
Writing application                      : Lavf58.29.100

Video
ID                                       : 1
Format                                   : VC-1
Format profile                           : Advanced@L3
Codec ID                                 : vc-1
Codec ID/Info                            : SMPTE VC-1
Duration                                 : 1 s 1 ms
Bit rate                                 : 477 kb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Variable
Frame rate                               : 29.970 (30000/1001) FPS
Minimum frame rate                       : 29.412 FPS
Maximum frame rate                       : 30.303 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Interlaced
Scan type, store method                  : Separated fields (2 fields per block)
Scan order                               : Top Field First
Compression mode                         : Lossy
Bits/(Pixel*Frame)                       : 0.008
Stream size                              : 58.2 KiB (97%)
Language                                 : English
Menus                                    : 2

vc1-interlaced.mp4