[mythtv] DVD playback issues, patch

Davin McCall davmac at davmac.org
Sun Nov 15 06:34:10 UTC 2009


That's odd, it sounds almost like the exact problem that the patch is 
meant to (and does, for me) fix. Basically, I was seeing video run at 
about 2x at the start (occasionally it would flatten out to normal speed 
after a few seconds, but the audio would then always lag the video).

Essentially the patch *should* make what you're seeing impossible. That 
is, if video gets ahead of audio then it gets slowed down, pretty much 
straight away, until they are in sync. So, I have no idea what's going 
wrong, it may be a decoder issue (wrong timestamps in the audio or 
video) or a media issue. What version of Myth did you apply the patch to 
(trunk, hopefully?)
Do you see the problem behaviour that you described on all DVDs?
And, if I sent you an updated version (with some debugs thrown in) would 
you be able to get the frontend log to me?

Davin


On 15/11/09 16:52, Johnny Stenback wrote:
> Davin McCall wrote:
>> Hi,
>>
>> What do you mean by "off by 2x" ... 2x what? Do you mean video is
>> playing twice as fast as audio (or the other way around)?
>> Or, does video lag audio by a consistent amount (2 frames, 2 seconds?)
>> or the other way around?
>
> Sorry for not clarifying that, what I see is that the video playback 
> speed is ~2x of the audio speed. Audio plays at normal speed as far as 
> I can tell, but video is ~2x too fast.
>
>> Thanks,
>>
>> Davin
>>
>>
>> On 15/11/09 04:36, Johnny Stenback wrote:
>>> Hello David,
>>>
>>> Thanks for digging in here. I haven't been able to test your patch on
>>> my primary system where I use VDPAU for playback yet, but I did test
>>> using software decoding and software rendering and it does not seem
>>> like your patch fixes the problem I'm seeing, and in a way it seems to
>>> make it worse :(
>>>
>>> Without your patch, if I fast forward for just a second after starting
>>> DVD playback, the audio/video speeds sync up and remains in sync from
>>> then on, but with your patch I can't seem to get audio and video to
>>> ever be in sync, it's always off by what looks like ~2x.
>>>
>>> I wish I could help more here, but I don't know this code at all and
>>> I'm unable to spend any serious time on this in the foreseeable future.
>>>
>>> Davin McCall wrote:
>>>> Here's an updated patch. The main change is that it avoids 
>>>> advancing the
>>>> vsync trigger if a frame is dropped. Otherwise, WaitForFrame will
>>>> effectively wait for the frame anyway, so dropping it has no effect.
>>>> This caused problems on some media files I have.
>>>>
>>>> Davin.
>>>>
>>>>
>>>> On 13/11/09 23:35, Davin McCall wrote:
>>>>> Hi all,
>>>>>
>>>>> Regarding the DVD playback issues I mentioned earlier. This is
>>>>> (possibly) related to the following tickets:
>>>>> http://svn.mythtv.org/trac/ticket/7067
>>>>> http://svn.mythtv.org/trac/ticket/7349
>>>>>
>>>>
>>>>
>>>> ------------------------------------------------------------------------ 
>>>>
>>>>
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