[mythtv-users] Losing audio after commercials

[mikerice1969 at comcast.net]

This is not a bug in MythTV but it is a problem that makes my MythTV enjoyment lower than it could be.  I know it is not a Myth problem since I have it with Tivo as well and had it before I even built my Mythbox...  It has been happening for a few months.  I am hoping someone else has seen this before or has ideas on how to fix it.

The Problem:
Recording going along fine for awhile then at the point where the commercial ends and it returns to the program the audio is lost.  Sometimes the audio is gone for the entire remainder of the program but at times returns at a future commercial/program transition.

Needless to say this means we cannot rely on the PVR to record programs and are forced to do evil things like recording it multiple times and (gasp) watching it on live TV.

Observations:
This seems to happen always (or almost always) after a commercial sequence where the cable company (Comcast) has inserted local ads, many times their own ads into the feed.  It therefore happens only on certain cable channels where they do this.  Normal network channels are not affected.   We've seen it quite frequently on the SCIFI channel and Family channel as we record those often.

I've actually watched LiveTV and observed this occurring.  I actually hear a brief flicker at these transition points and sometimes the sound is lost and sometimes it isn't.  

To get the sound back (if I happen to be watching) you can just change the channel on the cable box and return to the original channel and all is well.

Once we watched the show on two TVs, one with it recording on Tivo and one with no PVR attached.  It lost sound only on the Tivo'd TV.

Now I have a Mythbox downstairs and the Tivo upstairs and it occurs on both.

Possibilities:
1) Bad cabling?  Using basic coax cable into the cable box.  The same into the Mythbox/Tivo.   Since it happens to both Mythbox and Tivo I'd have at least two bad cables in this mix so that seems unlikely to me.  If you think it is the cables which cable?  line => cable box or cable box => PVR.  Any way to test a cable since this is not easily reproducible?

2) Signal strength problem?  The house has three cable in drops.  The downstairs TV is split once (one into cable box, one into TV).  There is a single unsplit line in the upstairs bedroom.  There is a line into the den what is used for cable internet and voip phone.  I don't know offhand how the signal is split outside the house to provide the three inputs inside.  A few months back we had a problem with some of the higher digital channels not coming in and the cable company came out and apparently put some type of amplifier in the garage to boost the signal.  In any case we are likely using more bandwidth than the average joe.  Does this sound like signal strength problem?  Any ideas how I can correct it?

Any other ideas?

Assuming I cannot track this down would a software solution be possible?  I haven't looked into this at all but would MythTV or the IVTV drivers (I am using a PVR-350) be able to detect the loss of audio and then tune the channel (or call the external channel changer) to restore audio?

I have a PVR-150 on the way (to add in addition to the 350) so it will be interesting to see if this problem occurs only through the cable box or also directly through a PVR tuner.

Any help would be appreciated.  I'd love to be able to correct this problem.  Thanks.