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

[John P Poet]

On Tue Nov 11 2014 at 11:43:29 AM Will Dormann <wdormann at gmail.com> wrote:

> 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?
>


Guaranteed is a strong word, but yes, having the HD-PVR do its own encoding
of the audio will result with it being in sync with the video the HD-PVR is
encoding.



> > 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?
>


Or pick a different provider.   One of the big factors that went into my
decision to go with Directv over Dish, was this issue.



> 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.
>

Yeah, good luck with that.

John
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