[mythtv-users] HDPVR audio out of sync in 5.1 AC-3 mode

[Bob Sully]

> Date: Sun, 27 Sep 2009 12:53:28 -0700
> From: Greg Zornetzer <gzornetzer.lists at gmail.com>
> Subject: Re: [mythtv-users] HDPVR audio out of sync in 5.1 AC-3 mode
>
> Hi Oz,
>
> On Sun, Sep 27, 2009 at 12:29 PM, Oz <ozdror at adelphia.net> wrote:
>
>>
>> When I change my Sat Box from PCM to Dolby digital and the HDPVR Audio
>> encoding to 4 (AC-3). The audio is significantly lagging behind the
>> video (possibly 2 seconds)
>>
> You cannot send 5.1 PCM over SPDIF (either toslink or digital coax) - only
> stereo PCM is available.  5.1 can only be sent over TOSLINK compressed as
> AC3 or DTS.  This is why you get only stereo when setting the box at PCM.
>
> Potentially dumb question - If you hook up the Sat box directly to the TV
> and the audio to a surround receiver, do you still observe the 2 second
> offset?  If so, it's the source's fault and not the HDPVR.
>
> -Greg

I have noticed this same problem when recording from the HD-PVR.  It seems
to be variably bad (sometimes almost no delay, other times bad enough
(say, 2 seconds or more, as noted above)) to make it annoying enough to
just delete the recording.

I am recording at 720p with the 5.1 optical input to the HD-PVR from the
STB.  I am recording (using a bash script I wrote) from the command line,
as I am not running trunk.  I am using JYA's version of 0.21-fixes, with
the VDPAU updates.  Before switching to the 5.1 optical output, I did NOT
have this problem when recording in stereo from the RCA inputs.   However,
I want to find a way to fix this rather than going back to 2ch audio, as
transcoding files with the 2ch audio track was problematic.

Unfortunately, I can't test this with my 5.1 stereo receiver, as its
optical audio inputs recently went to hell (I'm looking into a new
receiver).  The input from the Myth box into the receiver is via digital
coaxial, which does still work fine.  I do NOT get these delays with 5.1
recordings from the HD HomeRun or the pcHD-5500, so my guess is that it IS
the HD-PVR.  However, the recordings aren't consistently bad.

Anyone else have a clue as to what's causing this?

Thanks!
Bob

-- 
________________________________________
Bob Sully - Simi Valley, California, USA
http://www.malibyte.net
http://www.malibyte.com