[mythtv-commits] Ticket #9904: All black/incorrect previews

[MythTV]

#9904: All black/incorrect previews
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 Reporter:  beirdo                |          Owner:
     Type:  Bug Report - General  |         Status:  closed
 Priority:  minor                 |      Milestone:  0.25
Component:  MythTV - General      |        Version:  Trunk Head
 Severity:  medium                |     Resolution:  fixed
 Keywords:                        |  Ticket locked:  0
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Changes (by Github):

 * status:  new => closed
 * resolution:   => fixed
 * milestone:  unknown => 0.25


Comment:

 Fixed preview generation (at least for my case)

 Fixes #9904

 This was a death by many papercuts
 1) seeking to the end of file seems to miss the last entry in the
 recordedseek
    table.  I left this as is.
 2) seeking to the end of file does a linear search to find the frame.  The
 one
    thing I changed here was to make it actually fast-forward to the last
 known
    frame position before starting the search.  In the preview case, it was
    doing a linear search from frame 0 to the last frame in the file, which
 took
    longer than the timeout period.  This fixed the timeouts by jumping as
 far
    as we can first.
 3) we were seeking to the end of the file due to a uint64 overflow caused
 by
    doing an unqualified "frame - 1" even if frame was 0.  The MAX_UINT64
 value
    was then capped to the last frame number pre-seek.  I changed this to
 only
    subtract 1 if the value wasn't 0, and to use 0 if it was 0.
 4) we were asking for position 0 as the logic in the previewgenerator told
 it
    to.  if the value was 0 (which it always is on remote previews!), the
 code
    fell through to ask for frame 0 (which then got buggered by the above
    problems).  I changed the logic such that it would instead seek to 1/3
 into
    the program as we originally desired.

 Caveat:  I do not yet know how this will act with a recording in progress,
 however we do rebuild a preview (AFAIK) when the show finishes recording.

 I also don't know how the code changed such that this started happening,
 but
 whatever.  It seems to be fixed again.
  Branch:    master
  Changeset: 57b2cddc4d52a4231e1d441b510131e4090e68d9

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Ticket URL: <http://code.mythtv.org/trac/ticket/9904#comment:3>
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