[mythtvnz] Recordings without audio

[Austin Green]

On Sun, 06 Nov 2016 01:32:17 +1300
Stephen Worthington <stephen_agent at jsw.gen.nz> wrote:

> On Sat, 5 Nov 2016 21:44:35 +1300, you wrote:
> >Occasionally shows are recorded without any sound. Others on the same channel are fine. E.g.: TV3, recording 'Graham Norton' and (immediately following) '7 Days' - the first is OK, the second silent. I have two tuner cards; perhaps MythTV switches from one to the other between shows? The 'silent' problem only happens infrequently, maybe one show per month, so if it was a faulty tuner, I would expect to see it a lot more often. Anyone have any ideas?
> 
> As of MythTV 0.28, the database stores which card was used to make a
> recording.  If you use the I key twice on a recording and scroll down
> a bit, you see a field called "Recording Input".  This does rely on
> your having set the displayname field for each tuner when you created
> them.  If you did not do that, run mythtv-setup and add a displayname
> that is different for each tuner.
> 
> Also, check when you play a 'silent' recording if it has alternate
> audio tracks.  It may be that by default you are playing the wrong
> audio track, and if a particular recording has more than one, the
> others are not actually valid and do not have the proper sound.  Or
> possibly there is 5.1 or 7.1 sound and your sound setup does not
> handle that properly and produces no sound, where it works for a
> normal stereo sound stream.  While playing, M > Audio > Select audio
> track shows the list of available audio tracks.  Recent TV3 programmes
> usually have both an AC-3 5.1 audio track and an AAC stereo track.
> Older programmes (ones recorded a few years ago, but broadcast
> recently) may only have AAC stereo.  TVNZ 1 programmes seem to have
> both AAC and AC-3 audio, plus a second AAC audio track marked as
> Italian language.  I have a feeling that if you play the Italian
> audio, it will not actually be valid, but I have never actually tried
> that.
> 
> If you have a 'silent' recording hanging around still, then you might
> like to install the mediainfo package then run the mediainfo command
> on the file for that recording, and post the results.  To find the
> recording file for a particular recording, use the I command twice on
> it and scroll down to the "Recorded File Name" field.  Then look for
> that file in each directory where you store recordings.

Many thanks for that clear explanation. Doing the 'select audio track' fixed it, so at least I now have a work-around.

I'm a little puzzled that most times the same show is OK. Is is broadcast with different audio tracks on different occasions, or do I (as I suspect) have the default set differently for the two tuners, and the 'good' one is usually randomly chosen for the recording? Where can I set the default track to record/play?

I'll try the mediainfo next time I get a silent recording.