id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc	mlocked
12106	EIT: slow tuning on a channel restarts activescan (mplex eit starvation)	angela.schmid@…	Karl Egly	"I have a single tuner configured to active scan 35+ mplex. One mplex produces problems, that it takes 5+ seconds to tune a channel in 98% of the cases.
After (maybe just before) the EITTransportTimeout (3 minutes) on this mplex (channel 331) StartActiveScan is restarted.
As the starting channel is taken randomly and it stops frequently after scanning channel 331, the next mplex's (from activeScanChannels list) have a very small chance to be scanned (mplex eit starvation), causing them not to be scanned for a couple of days.

I added some debugging and reduced the channels to be actively scanned in eitscanner.cpp:
{{{
--- a/mythtv/libs/libmythtv/eitscanner.cpp
+++ b/mythtv/libs/libmythtv/eitscanner.cpp
@@ -119,7 +119,7 @@ void EITScanner::run(void)
         if (activeScan && (MythDate::current() > activeScanNextTrig))
         {
             // if there have been any new events, tell scheduler to run.
-            if (eitCount)
+            if (eitCount || true)
             {
                 LOG(VB_EIT, LOG_INFO,
                     LOC_ID + QString(""Added %1 EIT Events"").arg(eitCount));
@@ -130,7 +130,12 @@ void EITScanner::run(void)
             if (activeScanNextChan == activeScanChannels.end())
                 activeScanNextChan = activeScanChannels.begin();

-            if (!(*activeScanNextChan).isEmpty())
+                    LOG(VB_EIT, LOG_INFO,
+                        LOC_ID + QString(""Before looking for EIT data on ""
+                                         ""multiplex of channel %1"")
+                        .arg(*activeScanNextChan));
+
+                               if (!(*activeScanNextChan).isEmpty())
             {
                 eitHelper->WriteEITCache();
                 if (rec->QueueEITChannelChange(*activeScanNextChan))
@@ -222,6 +227,8 @@ void EITScanner::StopPassiveScan(void)
     eitHelper->WriteEITCache();
     eitHelper->SetChannelID(0);
     eitHelper->SetSourceID(0);
+
+    LOG(VB_EIT, LOG_INFO, LOC_ID + ""Stopped passive scan."");
 }

 void EITScanner::StartActiveScan(TVRec *_rec, uint max_seconds_per_source)
@@ -242,6 +249,7 @@ void EITScanner::StartActiveScan(TVRec *_rec, uint max_seconds_per_source)
             ""      useonairguide        = 1                AND ""
             ""      useeit               = 1                AND ""
             ""      channum             != ''               AND ""
+            ""      channum             in('331', '91', '146') AND ""
             ""      cardinput.cardid     = :CARDID ""
             ""GROUP BY mplexid ""
             ""ORDER BY cardinput.sourceid, mplexid, ""
@@ -298,4 +306,6 @@ void EITScanner::StopActiveScan(void)
         activeScanCond.wait(&lock, 100);

     rec = NULL;
+
+       LOG(VB_EIT, LOG_INFO, LOC_ID + ""Stopped active scan."");
 }
}}}

During the test no recordings were programmed. Two logs attached.
{{{
egrep ""Now looking for EIT data on multiplex of channel|EIT Events|StartActiveScan called with|Started"" \
    mythbackend.20140331000721.22379.log \
   >mythbackend.20140331000721.22379_1.log

egrep ""Now looking for EIT data on multiplex of channel|EIT Events|StartActiveScan called with|Started|Stopped|Locked"" \
    mythbackend.20140331000721.22379.log \
   >mythbackend.20140331000721.22379_2.log

}}}

The difference between ""Now looking for EIT data on multiplex of channel"" and ""Started passive scan"" shows the time to tune. 
Look at the end of the logs, where channel 331 took 4.5 seconds and scanning continued with the next mplex. All other scans on channel 331 caused StartActiveScan to restart.

Why does StartActiveScan stop run and restart? How can it be fixed?
"	Bug Report - General	closed	minor	29.2	MythTV - EIT	Unspecified	medium	fixed	eit mplex starvation		0