[Openchrome-users] opechrome tv-output shuffles fields

[nico berndt]

nico berndt schrieb:
> Hello everybody!
>
> I happily found the TV-Out of my VIA Epia EN12000EG to be one of the 
> rare cases to provide me with an unscaled and very good looking 
> PAL-picture. I was looking for such thing on a sbc for ages, since I 
> depend on proper TV-Outputs for my work.
> Sadly the TV-output is not all the way proper: It shuffles fields. Did 
> anybody notice this? Terry Barnaby wrote about the field order possibly 
> being changed, but it actually is worse.. I suppose you would not really 
> see this on a regular tv set, but when captured again you do.
>
> To explain a little deeper what I mean by shuffling fields:
> Proper video consists of frames consisting of even and odd fields: 
> [o1/e1] [o2/e2] [o3/e3] [o4/4] [o5/e5] [o6/e6]
> For progessive content, such as most DVD movies, both fields within a 
> frame sum up to a progressive frame again and the captured output should 
> again look line described above. But it looks like this [o1/e1] [o2/e3] 
> [o3/e3] [o4/e4] [o5/e6] [o6/e6]. I analyzed thousands of frames and 
> there is no pattern behind it, totally not! I don't quite understand 
> what is going on. I've seen video outputs mess up with the geometry and 
> badly shuffling fields, even starting the next field right in the middle 
> of another field, all torn, so this is not really a surprise. The 
> surprise is that the odd and even fields _always_ come in the right 
> order but from wrong frames! And that really bugs me, because I can not 
> image how this is happening. It looks like the encoder chips were surely 
> capable of doing everything right. One point that leads me to this 
> conclusion ist the stubburn order of the fields. Since it never mixes 
> up, I suppose the modelines to be very accurate. An often seen problem 
> is that the vga chip uses a refresh rate that is not exactly 50.00 Hz 
> (for PAL) and the encoder chip chokes up on trying to capture 50.10 Hz 
> into 50 fields.
>
> If tere is any interest I could privide my testvideo wich consists of 50 
> different frames displaying photos and large numbers from 01 to 25. The 
> position of the numbers changes all the time and there is also a stamp 
> "odd" or "even". "odd" is stamped into odd lines only, and "even" 
> accordingly. The whole thing comes as a dv type avi file, so the video 
> is I-frame only and the fields are encoded seperately. Having this and a 
> capture card one can spot errors immediately just by reading "number" 
> and o/e.
>
> So if there is any interest i'd provide this one and offer my help in 
> thinking and testing. I am no coder, sorry, no...
>
> Best regards and thanks to everyone involved building this driver!
>
> ../nico berndt
Nobody? Really? How comes? I can hardly imagine, I am the only one seing 
this...

Best regards,

../nico