Program title and/or description sometimes wrong

[klaas@…]

MythTV guide data, as received from DVB-C, has incidentally a wrong program title and/or a wrong program description. Attached is a picture of my TV recordings, showing the program title "Live motorsport" (which is OK) with a description of a football match in South Korea (which is NOT OK). Attached is also a picture from the guide of the TV itself which shows the correct program description. This is caused by a few lines in libs/libmythtv/programdata.cpp that only accepts updates for title, subtitle and description fields of EPG data when the new EPG data for these field is LONGER than the previously received data for that field. This means that, for example, the broadcaster does change its programming and does change "Live Motorsport" to "Football" the title of the program will never change to "Football" in MythTV because the title is shorter. As a result, recording rules based on string pattern matching of title and/or description can fail to record the correct program. This bug has been in MythTV since about the year zero.

Details: This happens in UpdateDB, starting at line 616. This function is called when existing program data is to be replaced by new data. In this function the old program data is updated on a field by field basis. Attached is a fixed version in which the new data completely replaces the old data.

This has been tested with my DVB-C signal (Ziggo in The Netherlands) but it has not been tested with DVB-T or DVB-S.

[klaas@…]

wrong program description on mythtv

[klaas@…]

correct program description on TV guide

[klaas@…]

libs/libmythtv/programdata.cpp with fix

[klaas@…]

libs/libmythtv/programdata.cpp with fix and with lots of debug code

[Stuart Auchterlonie]

Klaas,

Can you do a git diff to capture the changes to programdata.cpp please?

Regards Stuart

[klaas@…]

Created pull request for my commit 0c66e7f298eac4ebf60d047e3efb4fb7c5844b32

[klaas@…]

git diff of final version, identical to pull request

[Klaas de Waal]

Updated the patch for today's master.
The changes are now limited to title/subtitle/description and airdate.

The existing code for title/subtitle/description compares the string as stored in the database with the newly received string and uses the longest. This is wrong as already documented in the original bug report.
This patch copies the old value of title/subtitle/description only if there is no new value but there is an old value.
Example: the modification for the title:

-    if (match.title.length() >= ltitle.length())
+    if (ltitle.isEmpty() && !match.title.isEmpty())
         ltitle = match.title;

N.B. The code for title/subtitle/description update is copied from branch fixes/0.27 of the mythtv fork of dcjm/David Matthews. He apparently found this bug also but he has not submitted a ticket for this AFAIK.

The attached patch does also have a correction for the update of the airdate:

-    if (!lairdate && !match.airdate)
+    if (!lairdate && match.airdate)
         lairdate = match.airdate;

The old code uses the old airdate only if the newly received airdate and the old airdate are both zero. This is obviously a mistake. The new code uses the old airdate only if the new airdate is zero and the old airdate is not.

[Klaas de Waal]

Fix for update of title/subtitle/description and airdate.

[Klaas de Waal <kdewaal@…>]

In 62ae08961/mythtv:

Update guide title/subtitle/description with new DVB EIT data

The title/subtitle/description in the guide is now updated
with the latest information received from DVB EIT. The title
is now updated with the newly received data unless the new
title is an empty string.
Previously, the title was only updated if the new title was
longer than the old title. This caused missed recordings when
recording rules are used that refer to the program title.
The same for the subtitle and the description.

Fixes #13057