[mythtv-users] HD-PVR dropped frames / MythTV AV glitches

[Will Dormann]

Hi John,

On 11/11/14 10:53 AM, John P Poet wrote:
> Are you using the S/PDIF input on the HD-PVR, or the analog input?  If
> it is the S/PDIF input, try the analog and see if the problem goes away. 

Ahh, you might be on to something here!   Since I obtained a digital
amp, I switched to S/PDIF (optical) to retain 5.1 audio from start to
1d2finish.   And now that I think about it, I suspect that around this
time was that I started noticing audio glitching.   But given the number
of changes that happened around that time, I never really drew a 1-to-1
mapping about cause / effect.    My suspicion was that the audio was
perhaps always glitching, but I was only just noticing it because of the
new amp and hookups.


> When using the S/PDIF, the HD-PVR muxes the digital audio into the video
> without modification.  If you use the analog inputs, then the HD-PVR
> converts it to digital before muxing it in -- encoding the audio.

Good to know.   So basically, with analog audio you're more guaranteed
to have a valid video stream with proper A/V sync?


> Myth uses the audio for timing and synchronization.  If the audio has
> any glitches in it, it can cause the kind of problem you are
> describing.  If you are using S/PDIF and switching to analog fixes it,
> then your cable company is sending you bad digital audio.

I'll try switching back to analog audio input to the HD-PVR to see how
it works.   If it works, then I guess I'll have to decide between
glitchy digital 5.1 and smooth analog pro logic audio, right?

If it is Comcast's fault that the audio isn't perfect, I am skeptical
that I could ever talk to anybody who would be able to know and/or do
anything about.


Thanks
-WD