[Openchrome-users] opechrome tv-output shuffles fields

[nico berndt]

Christiaan van Dijk schrieb:
> Hi Nico,
>
> I'm familiar with the swapped field problem on the via boards and yes, 
> this is very annoying.
> The problem seems to come from the TV encoder which has no (known) 
> method of indicating which field it is displaying. The video driver 
> therefore has to guess if it's displaying an odd or even frame.
> When playing MPEG2 with XvMC this can be solved by using the BOB 
> deinterlace method. This method doubles the frame rate and somehow the 
> TV encoder can pick the right field, I don't have any details on how 
> this works but the result looks good. So use deinterlacing to display 
> interlaced material on an interlaced screen :-\ 
> When using standard video playback also deinterlace, BOB is giving me 
> troubles with MythTV so I use kernel for playback of non MPEG2 material 
> (myth always uses BOB in case of XvMC).
> Frame rates have to match so use the right modeline, can be tricky, mine 
> is still shifted a bit too much to the left.
>
> I wanted to see if there are tricks with the TV encoder to get the field 
> information but via is not very willing to share datasheets :-(
>
> Well that's my experience with this stuff. I think there have to be ways 
> to really solve the issue but I don't have the information to figure it 
> out. Would for example be very nice to add a component out to the board 
> which the TV encoder seems to have.
>
> Regds,
> Christiaan.
>   
Hi Christian,

good someone has the same interest.

The problem goes beyond only swapped fields, some are missing! I 
described that in my initial post, the field order looks something like 
this:

[o1/e1] [o2/e3] [o3/e3] [o4/e4] [o5/e6] [o6/e6]

You can see that for instance field even 5 is simply miissing. Aonther 
thing you can see is that the actual order of the fields is always kept 
correct. Odd, even, odd, even, odd.... Even if a field is missing, this 
order os strictly kept! That causes a visible swap of order, I guess 
that is what you see. This would mean that the actual information about 
odd/even fields /is/ known to the driver.

Do you have a capture card? I could send you my test video which makes 
it absolutely clear. You see the frame numbers as well as the odd/even 
information.

If you are interested I could also send you some captured fields for 
analysis.

What shall we do? - I'd really like to understand what is happening 
inside the tv-output chain in order to help improving the driver to work 
correctly.

Regards,
../nico