This is wot broke it:

 commit 9d7538247ff1bf9841b53eeb71ddc47f2c662415
 Author: Sebastian Dröge <sebastian.droege@collabora.co.uk>
 Date:   Tue May 18 08:45:52 2010 +0200

    playbin2: Don't put "raw" subtitle types in the raw caps for decodebin2
    
    We handle them from the autoplug-continue signal, where the caps supported
    by the subtitle sink or overlay are known already.

When it's working (uridecodebin's caps default to include video/x-dvd-subpicture):

gsturidecodebin.c:1631:source_new_pad:<uridecodebin0> Found new pad source.subpicture in source element source
gsturidecodebin.c:1634:source_new_pad:<uridecodebin0> configured raw caps: video/x-raw-yuv; video/x-raw-rgb; video/x-raw-gray; audio/x-raw-int; audio/x-raw-float; text/
plain; text/x-pango-markup; video/x-dvd-subpicture; subpicture/x-pgs
gsturidecodebin.c:1046:has_all_raw_caps:<source:subpicture> have caps video/x-dvd-subpicture
gsturidecodebin.c:794:new_decoded_pad_cb:<source> new decoded pad, name: <subpicture>. Last: 0
    gstplaybin2.c:2466:pad_added_cb:<playbin20> pad uridecodebin0:src1 with caps video/x-dvd-subpicture added in group 0xa05480
    gstplaybin2.c:2492:pad_added_cb:<playbin20> creating new selector


Not working:


gsturidecodebin.c:1631:source_new_pad:<uridecodebin0> Found new pad source.subpicture in source element source
gsturidecodebin.c:1634:source_new_pad:<uridecodebin0> configured raw caps: audio/x-raw-int; audio/x-raw-float; video/x-raw-yuv; video/x-raw-rgb; video/x-raw-gray
gsturidecodebin.c:1046:has_all_raw_caps:<source:subpicture> have caps video/x-dvd-subpicture
gsturidecodebin.c:1651:source_new_pad:<source:subpicture> not all raw caps, plugging decoder
gsturidecodebin.c:1359:make_decoder:<uridecodebin0> making new decodebin2
  gstdecodebin2.c:1041:gst_decode_bin_set_caps:<decodebin20> Setting new caps: audio/x-raw-int; audio/x-raw-float; video/x-raw-yuv; video/x-raw-rgb; video/x-raw-gray
  gstdecodebin2.c:1095:gst_decode_bin_set_subs_encoding:<decodebin20> Setting new encoding: (NULL)
  gstdecodebin2.c:1097:gst_decode_bin_set_subs_encoding:<decodebin20> subtitle locking from thread 0x20f7520
  gstdecodebin2.c:1097:gst_decode_bin_set_subs_encoding:<decodebin20> subtitle lock from thread 0x20f7520
  gstdecodebin2.c:1106:gst_decode_bin_set_subs_encoding:<decodebin20> subtitle unlocking from thread 0x20f7520
gsturidecodebin.c:1422:make_decoder:<uridecodebin0> have 2 pending dynamic objects
gsturidecodebin.c:1662:source_new_pad:<uridecodebin0> linked decoder to new pad
  gstdecodebin2.c:3500:gst_decode_bin_change_state:<decodebin20> dynlocking from thread 0x20f7520
  gstdecodebin2.c:3500:gst_decode_bin_change_state:<decodebin20> dynlocked from thread 0x20f7520

commit 115e503bdf03b7da241965c41be8dc401aec6b52
Author: Sebastian Dröge <sebastian.droege@collabora.co.uk>
Date:   Tue Jul 6 09:47:45 2010 +0200

    Revert "playbin2: Don't put "raw" subtitle types in the raw caps for decodeb
    
    This reverts commit 9d7538247ff1bf9841b53eeb71ddc47f2c662415.
    
    If the DVD subpicture caps are not part of the raw caps, uridecodebin
    doesn't qualify resindvdbin as raw source and plugs decodebins, which
    causes broken DVD playback because of bugs elsewhere.
    
    This change was originally added to only expose supported, raw subtitles,
    e.g. if the subtitle sink did not support DVD subpictures but a converter
    to some supported format exists. It's not very important right now because
    we have nothing (that is autoplugged) to convert from plaintext/pango-markup
    or DVD subpictures to something else.
    
    Fixes bug #623583.