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

[Karl Newman]

On Thu, Feb 28, 2013 at 8:05 AM, Paul Gardiner <lists at glidos.net> wrote:

> 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<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.
>

Some TVs can do video processing which can induce delay. Usually there's a
setting or a mode which disables this (something like Game Mode should do
it). This may not be the cause of your problem, but it might be worth
looking into.

Karl
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