[mythtv-users] Video is behind audio, dropping frames to catch up (VDPAU, HD content)

[Paul Gardiner]

On 28/02/2013 15:39, Mike Perkins wrote:
> On 28/02/13 12:15, Paul Gardiner wrote:
>> On 28/02/2013 12:01, Mike Perkins wrote:
>>> On 28/02/13 08:23, Paul Gardiner wrote:
>>>> On 27/02/2013 22:04, Thomas Börkel wrote:
>>>>> HI!
>>>>>
>>>>> I have now tried many things, but I am running out of ideas.
>>>>>
>>>>> * it happens usually every 2-10 minutes
>>>>> * it happens for HD h264 and SD MPEG2, just for HD a little more often
>>>>> * it happens with and without VDPAU
>>>>> * it happened on old and upgraded hardware (only sound card identical)
>>>>> * it happens on 0.26 and earlier versions
>>>>> * I have tried all VDPAU profiles
>>>>> * I have disabled logging over NFS (> /dev/null)
>>>>> * I have enabled realtime prio (but it is not mentioned in the log)
>>>>> * I have reniced mythfrontend to -2 and X to -12
>>>>> * I have set the GPU to max. frequency all the time, so no switching
>>>>> * I have disabled the often crashing mythlcdserver
>>>>> * I have tried different kernel and NVidia driver versions
>>>>>
>>>>> What else can I try? What more info should I provide?
>>>>>
>>>>> Probably, something needs a little CPU time every now and then and
>>>>> this
>>>>> probably causes that little "jump" in playback and the log entry from
>>>>> the subject, but I don't know what it is and why MythTV is so
>>>>> sensitive
>>>>> on such hardware specs (Core i3, 3.1 GHz)?
>>>>>
>>>>> Or does it probably have something to do with the fact that this is a
>>>>> diskless PXE frontend?
>>>>>
>>>>> Any hints would be greatly appreciated.
>>>>
>>>> None of the myth systems I've built have ever synchronized AV
>>>> correctly.
>>>> I've always had to pause and unpause every now and then to regain sync
>>>> and even then it's to get it to a consitentish 100ms which I then
>>>> correct within my AV receiver. It's odd, because every other player
>>>> I've
>>>> tried with my recordings or downloads show them correctly in sync.
>>>>
>>> My diskless PXE frontend has never had problems with AV sync. I use NFS
>>> to mount the root but not for media directories. On the other hand, my
>>> sound comes out the TV. Perhaps it is the "AV receiver" which is the
>>> common variable?
>>
>> I have wondered that. I will test, although several of the myth systems
>> I was referring to were connected direct to speakers, and the sync was
>> always variable and depended on the last user command. I think my
>> current frontend may be pretty much ok when I'm not using different
>> screen modes for different video resolutions, but I'm not sure of that.
>> Need to do more testing.
>>
>> What CPU are you running?
>>
> My current front end is one of these:
>
> http://www.newegg.com/Product/Product.aspx?Item=N82E16813131663
>
> That outputs via HDMI. A previous incarnation had a C7 VIA chip which
> output using VGA and 3.5 mm stereo into the TV. No problems either way.

Nice. Will that do HQ scaling and Advanced 2x deinterlacing? Maybe I
should upgrade. In any case, you are using an Atom too, so the A/V
sync problem isn't down to processing power.

Just realised that with my current set up, it will be difficult to
remove the AV receiver: it's my only AMP, and the TV has no speakers.
I can try moving to HDMI audio from spdif again, but last time I
tried that it made sync worse. I never have sync problems with
my blu-ray player, so I sort of doubt it is caused by the amp,
but I'd like to rule it out. I guess I just need to borrow a little
mobile speaker from someone.

BTW, do you know what the "playback details" display measures A/V
sync in?

P.