[mythtv-commits] Ticket #9437: dvd iso playback with storage groups (long loading time)

[MythTV]

#9437: dvd iso playback with storage groups (long loading time)
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 Reporter:  kloana@…                 |          Owner:  stuartm
     Type:  Bug Report               |         Status:  assigned
 Priority:  minor                    |      Milestone:  unknown
Component:  MythTV - Video Playback  |        Version:  0.24-fixes
 Severity:  medium                   |     Resolution:
 Keywords:  iso playback loading     |  Ticket locked:  0
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Comment (by cpinkham):

 I've attached a patch 9437_remote_dvd_speedup_v1.diff that has
 significantly improved my remote DVD playback startup speed.

 The first part of the patch tries to fix an issue where an immediate read
 after an optimized backwards seek is locked waiting for more data to be
 read from the backend even though the required data is actually already
 inside the ringbuffer.  Adding this fix cut my remote DVD startup times by
 30% or more.

 The second part of the patch is only applicable to VIDEO_TS and BDMV
 directories.  This patch tightens the restrictions for using a remote file
 optimization.  In the current code, we use a RemoteFile object for remote
 files less than 50KiB in size.  In testing, I noticed that the DVD nav
 code often seeked backwards in the same file and reread the same data.
 When using a RemoteFile, we do not have the benefit of a local data cache,
 so these backwards seeks require re-reading the data from the backend.
 The patch changes this filesize threshold to 512 bytes so that we use a
 RingBuffer (and it's built in cache) for files >= 512 bytes in size.  This
 part of the patch also improved playback startup speed for me for VIDEO_TS
 and BDMV directories.

 The second part of the patch is a trivial change and should not have any
 negative effects.  The first part of the patch regarding optimized
 backwards seeks has been tested, but is not installed on my production
 systems currently.  Daniel wants to look at this part of the patch further
 before this could be rolled into master, but I wanted to provide a copy in
 this ticket so that others could test it if they want to do so.

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Ticket URL: <http://code.mythtv.org/trac/ticket/9437#comment:11>
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