[mythtv-users] HD-PVR Audio Sync Issues After Channel Change

[John P Poet]

On Mon, Apr 12, 2010 at 4:56 PM, Alan Young <ayoung at teleport.com> wrote:
> On 04/12/2010 03:47 PM, Kevin Ross wrote:
>>>
>>> My HD-PVR pretty much works wonderfully until I change the channel, at
>>> which point the audio goes way out of sync. I'm running latest svn and
>>> have tried various versions of the firmware to no avail.
>>>
>>> I'm changing channel via firewire on an SA3250 using sa4250_ch - I
>>> couldn't get the 3250 to work properly. There's no significant errors
>>> on front or backend, so I'm not entirely sure where to look.
>>>
>>> Could it be an issue with the channel change script (I don't see how)
>>> or is there something else that could be the culprit.
>>>
>>> Thanks!
>>
>> In my experience, Live TV isn't usable with an HD-PVR until you apply the
>> patches listed in the wiki.  Adding a few seconds to the channel change
>> script helps, but it isn't perfect.  Adding a delay isn't necessary with
>> the
>> patches (in my experience).
>
> The patches in the wiki are a band-aid.  They stop and restart the recorder
> after the channel change.  It flushes the HDPVR buffers of data and any
> pending data on the PC.  That's why back to back recordings end up missing
> several seconds.

What those signal monitor patches do:

1) Tell the HD-PVR to start recording
2) Test the output of the HD-PVR to see if a valid resolution is being reported
3) If a valid resolution is not reported, or if data is not
forthcoming in a timely manner then reset the HD-PVR driver and goto
step 1
4) Tell the HD-PVR to stop recording, and continue on to the actual
recording process.

As part of the process, the "state" is reported to the frontend, so
the user can see what is going on and abort if there is a serious
problem.  This also prevents the frontend from timing out, if the
channel change process takes more than 15 seconds.  The user can abort
LiveTV or try another channel at any time during the process.

Because the signal monitor patches effectively try to briefly record
something, someone watching the status light on the HD-PVR would see
it record, stop, and then record again.  The idea is, that when the
actual recording process starts up, there is a very high chance that
the STB and HD-PVR are in a happy state.

Even without those patches, Myth's HD-PVR recording process will issue
"stop recording"/"start recording" commands to the HD-PVR driver, if
it does not see a steady stream of data from the HD-PVR>

John
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