Revision as of 21:08, 23 September 2008

It is possible that the seektable can become corrupted for one or more recordings, which can result in:

• Being unable to skip forward and backward correctly, and
• Recordings reporting the incorrect length.

mythcommflag and mythtranscode are two tools that can be used to rebuild the seektable.

Note: After rebuilding the seektable, any cutlist which has created for a recording will no longer be properly synced and should be recreated.

Repairing the Seektable

Preparation

First, run the optimize_mythdb.pl script to ensure that the MySQL database is in good order. This script should be run by a user with a valid ~/.mythtv/config.xml, which provides the required the database connection information. Since ~/.mythtv/config.xml is also used by mythfrontend and will be created by mythfrontend if it doesn't already exist, running optimize_mythdb.pl as a user who has previously run mythfrontend is recommended.

On an Ubuntu machine, for example, running optimize_mythdb.pl is as simple as running the following command:

/usr/share/doc/mythtv-backend/contrib/optimize_mythdb.pl

This will iterate through each of the tables in the mythconverg database, 'optimizing' each one. Once the optimize_mythdb.pl script has returned successfully, it is time to move on.

Using mythcommflag

mythcommflag is generally very successful and very efficient at rebuilding the seektable.

For each recording with corrupted seektable in need of repair, run the following command:

mythcommflag --file <filepath> --rebuild

where <filepath> is the path to a recording that exists in the Myth TV database. There are other options that can be used to specify the input filename(s), refer to the mythcommflag page for further details.

Note: mythcommflag should always be used for files that are recording in or transcoded to NUV.

Using mythtranscode

If problems are encountered rebuilding a seektable with mythcommflag, try using mythtranscode as follows:

mythtranscode --mpeg2 --buildindex --allkeys --showprogress --infile <filepath> 

where <filepath> is the path to a recording that exists in the Myth TV database. There are other options that can be used to specify the input filename, refer to the mythtranscode page for further details.

It should be noted that mythtranscode generally does a better job at repairing MPEG-TS (and/or MPEG-PS) streams.

Possible Causes of a Corrupt Seektable

• Editing a recording outside of the MythTV Frontend.
• Excessive disk IO during recording could prevent invalid SQL updates to the recordedseek table (I think).
• Crashed MySQL tables.
• Losing the network between slave backends and the MySQL database server during recordings.
• Alternatively, files imported into the MythTV recordings library may need to have their seektables built, especially if they are to be edited.