Difference between revisions of "Duplicate matching"

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MythTV will, unless you tell it otherwise, try and not record programs that have already been recorded.  There are four different methods it can use to determine if a program is a duplicate.
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MythTV will, unless you tell it otherwise, try to record each episode of a show only once.  To do so, MythTV compares showings in the listings that match recording rules to information about previously-recorded episodes (watched, unwatched, or deleted) of the program, checking for duplicatesThe primary mechanism for duplicate matching is comparing program IDs, and there are four "fallback" methods.
  
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== Program ID ==
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The program ID is the definitive identifier of an episode.  If the current episode described in the listings and a previously-recorded episode both have non-generic program ID's, then only the program ID will be compared to determine if the program is a duplicate.  In this case the duplicate-matching method specified by the recording rule will be ignored.  If the program ID's are identical, MythTV will not record the new showing; if they are not identical then the episode will not be considered a match and MythTV will record it provided there are no other matching previously-recorded programs.
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If the episode is a generic episode (for example, a Schedules Direct program ID of the format SH*0000), MythTV will record the episode, without regard to the program ID or duplicate-matching method specified by the recording rule.  A generic episode, by definition, means that an unknown episode is airing, so it is impossible for anyone--including MythTV--to know if it has been recorded before.  Therefore, MythTV will always record generic episodes, just in case.  If you want to exclude generic episodes, you must specify a filter (such as "Exclude unidentified episodes") for the duplicate matching scope in the recording rule.
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If either the current episode described in the listings or the previously-recorded episode (or both) are missing a program ID, duplicate matching will be performed according to the duplicate-matching method specified by the recording rule.
  
 
== Subtitle ==
 
== Subtitle ==
The scheduler will compare the subtitles of the new epsiode with any recorded (watched, unwatched or deleted) episode and if they match then it will not record the new showing.
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If the subtitle of the new episode and any previously-recorded episode match exactly, MythTV will not record the new showing.
  
 
== Description ==
 
== Description ==
The scheduler will compare the description of the new epsiode with any recorded (watched, unwatched or deleted) episode and if they match exactly then it will not record the new showing.
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If the description of the new episode and any previously-recorded episode match exactly, MythTV will not record the new showing.
  
 
== Subtitle and Description ==
 
== Subtitle and Description ==
The scheduler will compare the subtitles and description of the new epsiode with any recorded (watched, unwatched or deleted) episode and if they both match exactly then it will not record the new showing.
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If both the subtitle and description of the new episode and any previously-recorded episode match exactly, MythTV will not record the new showing.
  
 
== Subtitle then Description ==
 
== Subtitle then Description ==
The scheduler will compare the subtitles of the new epsiode with any recorded(watched,unwatched or deleted) episode and if they match exactly then it will check the description and only if the descriptions are also identical then it will not record the new showing.
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If the new episode has a subtitle and the subtitle of the new episode and any previously-recorded episode match exactly, MythTV will not record the new showing.
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Otherwise, if the new episode does not have a subtitle and the description of the new episode and any previously-recorded episode match exactly, MythTV will not record the new showing.
  
 
== FAQs ==
 
== FAQs ==
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Q. But all of the episodes have the same programid.
 
Q. But all of the episodes have the same programid.
  
A. True, but all three episodes have a SH*0000 programid -- the Schedules Direct programid used for generic episodes -- meaning which episode is airing is unknown.  Rather than ignore this episode -- just because the
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A. True, but all three episodes have a SH*0000 programid -- the Schedules Direct programid used for generic episodes -- meaning which episode's airing is unknown.  Rather than ignore this episode -- just because the
 
listings provider wasn't given information on which episode was airing -- MythTV will record it.
 
listings provider wasn't given information on which episode was airing -- MythTV will record it.
  
 
The scheduler gives special treatment to any generic episodes (always recording them in case they're new).  Schedules Direct/TMS data uses programid's of the form SH (for show) followed by some digits identifying the program (title) and ending with 4 zeros (meaning unknown episode).  If you want MythTV to skip recording generic episodes, you need to explicitly set the recording rule to "Exclude Generic Episodes."
 
The scheduler gives special treatment to any generic episodes (always recording them in case they're new).  Schedules Direct/TMS data uses programid's of the form SH (for show) followed by some digits identifying the program (title) and ending with 4 zeros (meaning unknown episode).  If you want MythTV to skip recording generic episodes, you need to explicitly set the recording rule to "Exclude Generic Episodes."

Latest revision as of 16:38, 20 March 2013

MythTV will, unless you tell it otherwise, try to record each episode of a show only once. To do so, MythTV compares showings in the listings that match recording rules to information about previously-recorded episodes (watched, unwatched, or deleted) of the program, checking for duplicates. The primary mechanism for duplicate matching is comparing program IDs, and there are four "fallback" methods.

Program ID

The program ID is the definitive identifier of an episode. If the current episode described in the listings and a previously-recorded episode both have non-generic program ID's, then only the program ID will be compared to determine if the program is a duplicate. In this case the duplicate-matching method specified by the recording rule will be ignored. If the program ID's are identical, MythTV will not record the new showing; if they are not identical then the episode will not be considered a match and MythTV will record it provided there are no other matching previously-recorded programs.

If the episode is a generic episode (for example, a Schedules Direct program ID of the format SH*0000), MythTV will record the episode, without regard to the program ID or duplicate-matching method specified by the recording rule. A generic episode, by definition, means that an unknown episode is airing, so it is impossible for anyone--including MythTV--to know if it has been recorded before. Therefore, MythTV will always record generic episodes, just in case. If you want to exclude generic episodes, you must specify a filter (such as "Exclude unidentified episodes") for the duplicate matching scope in the recording rule.

If either the current episode described in the listings or the previously-recorded episode (or both) are missing a program ID, duplicate matching will be performed according to the duplicate-matching method specified by the recording rule.

Subtitle

If the subtitle of the new episode and any previously-recorded episode match exactly, MythTV will not record the new showing.

Description

If the description of the new episode and any previously-recorded episode match exactly, MythTV will not record the new showing.

Subtitle and Description

If both the subtitle and description of the new episode and any previously-recorded episode match exactly, MythTV will not record the new showing.

Subtitle then Description

If the new episode has a subtitle and the subtitle of the new episode and any previously-recorded episode match exactly, MythTV will not record the new showing.

Otherwise, if the new episode does not have a subtitle and the description of the new episode and any previously-recorded episode match exactly, MythTV will not record the new showing.

FAQs

Q. I chose the duplicate check method 'Subtitle and Description,' and a set of episodes have the same subtitle and description, yet I still get duplicates.

A. All of those episodes also have a programid, and when episodes have a programid, the duplicate check method is irrelevant. Only the programid is used for comparison because the programid is the definitive identifier of an episode.

Q. But all of the episodes have the same programid.

A. True, but all three episodes have a SH*0000 programid -- the Schedules Direct programid used for generic episodes -- meaning which episode's airing is unknown. Rather than ignore this episode -- just because the listings provider wasn't given information on which episode was airing -- MythTV will record it.

The scheduler gives special treatment to any generic episodes (always recording them in case they're new). Schedules Direct/TMS data uses programid's of the form SH (for show) followed by some digits identifying the program (title) and ending with 4 zeros (meaning unknown episode). If you want MythTV to skip recording generic episodes, you need to explicitly set the recording rule to "Exclude Generic Episodes."