[mythtv] Ticket #9854: ISO playback problems

[Jim Stichnoth]

On Sun, Jun 19, 2011 at 5:31 AM,  <noreply at mythtv.org> wrote:
> #9854: ISO playback problems
> ------------------------------------------------+--------------------------
>  Reporter:  Jim Stichnoth <stichnot@…>          |          Owner:  markk
>     Type:  Bug Report - General                |         Status:  accepted
>  Priority:  minor                               |      Milestone:  0.25
> Component:  MythTV - Video Playback             |        Version:  Trunk
>  Severity:  medium                              |  Head
>  Keywords:                                      |     Resolution:
>                                                |  Ticket locked:  0
> ------------------------------------------------+--------------------------
>
> Comment (by markk):
>
>  > 2. ISOs with several titles take a long time to start up, and also to
>  jump to the main menu.  See attached mythfrontend2.log output, where the
>  time between 06:55:32 and 06:56:08 (36 seconds) is spent on the "Please
>  Wait...." screen.
>
>  This is a known issue that I've spent far too long trying to resolve. When
>  playing back over a storage group, the libmythdvdnav object gets a
>  RemoteFile object from mythtv to load the iso over the network. This uses
>  a readahead thread to buffer playback but it is painfully inefficient at
>  dealing with the various seeks and file checks that libmythdvdnav needs to
>  do when examining the file structure etc. Blu-ray playback has a similar
>  problem.
>
>  The quick and dirty fix is to not use the readahead thread. This will
>  generally reduce startup times to less than a second but you will almost
>  certainly get playback issues due to the lack of buffering - especially at
>  cell boundaries.
>
>  If anyone has any other suggestions, I'm all ears.

Just to be clear, I should point out that this long delay issue is a
new one, certainly less than a month old.  I assume it's a result of
the recent RingBuffer improvements, but I don't know if ISO
performance degraded because the readahead thread is new or because
its heuristics have changed.  Unlike #9437, I'm seeing the big delays
when there are only a handful of titles in the ISO, like 9 titles, and
I'm using a gigabit network in contrast to that ticket's 100 Mb
network.  If you still think this is the same issue, please close the
ticket (and I'll open a new ticket regarding issue #3 (and sorry about
the 3-in-1 bug report)).

BTW, another quick and dirty "fix" is to use NFS instead of storage groups...

Jim