[MPlayer-users] composite input a/v sync issue

[Miroslav Rovis]

> On Thu, Nov 05, 2009 at 05:50:08PM +0100, Miroslav Rovis wrote:
>   
>>>> mencoder -fps 25 -ofps 25 -noskip -mc 0 -vf harddup,softskip tv:// -tv
>>>> input=1:driver=v4l2:device=/dev/video0:normid=3:input=1:alsa:adevice=hw.0:audiorate=48000:amode=1:width=768:height=576
>>>> -ovc lavc -lavcopts vcodec=mpeg4:autoaspect:vbitrate=8000 -oac mp3lame
>>>> -srate 48000 -lameopts cbr:preset=standard -endpos 100  -o VHS155_`date
>>>> +%H%M%S`.avi
>>>>     
>>>>         
>>> While I do not know if it can even work without, -fps 25 tells
>>> MPlayer/mencoder to assume that there are always exactly 25 frames per
>>> second. If the capture card loses sync during the bad sections and does
>>> not produce any frames that is of course not going to work out at all.
>>>
>>>   
>>>       
>> Thanks for trying to help. 25 frames per second is the PAL standard,
>> it's by the book and by the google that anyone, as far as I had searched
>> earlier, capturing PAL VHS on composite input do (some even recommend
>> -fps 50)...
>>     
>
> No, you misunderstand: -fps 25 tells MPlayer to assume the input to be
> _exactly_ 25 fps no matter what, ignoring completely when the data arrives
> from the capture card.
> If you have a broken part in the video, it will not be able to capture _any_
> frames, so during that time it is actually 0 fps, and with -fps 25 you explicitly
> _forbid_ MPlayer to correct this.
> There is also a fps option for -tv which is something else and which is supposed
> to work in a saner way.
> Still, to handle it properly you'd need support for variable frame-rate in-/output
> which MPlayer does not have.
>
>   
I see now. Thanks for bearing up with me so nicely. Sincerelly I say!
Thanks in the first place.
I'll be back after I've looked into the matter with more clarity now,
thanks to your patient explanation. Trials follow... Aaarrghhh!