[pxc] Re: Unsynced Images.

[Alessandro Rubini]

[Marius' post, that I quote, has not been approved by mailman
 because it's too big. If someone is interested, I placed
 the attached image in ftp://arcana.linux.it/private/unsynched.png ]


> I just though I'd show you a picture and get your opinions. I've
> just completed the support for full/interlaced frames in my
> applications, and something has become more aparent. It seems that
> the Generic Bt878 card that I am using does not seem to sync to the
> propper field. This picture is acquired using mmap, and I have used
> both the 0.80 and 0.81 drivers, with the same result.

> It seems to swap the fields about 50% of the time.

Very strange. I never got the same problem. I'll look better and will
send you some code/patch to try and help diagnosing the problem.

> Acording to your documentation, it will always start capture on the
> first field (for capturing single fields to avoid jitter), and I
> asume it the same with frames.  (PS My single fields do not seem to
> do this, resulting in constant jitter)

I remember this. It's in my queue. Hope to have time next week, I'm sorry
I can't looks at it earlier.
 
> What can I do to minimise this? Is there a way I can check what
> field I'm grabbing?

It's written in the interrupt status flag. You might try to print
it when the buffer is committed, to check whether the hardware is
mistaking one field for the other or if there's a bug.

Since it doesn't happen always (in high res), I think it's a problem
with the specific camera you are using.

BTW: I'll try with both PXC200 and plain-878 device.

/alessandro

> ------=_NextPart_000_0000_01C1BDD4.FC367BB0
> Content-Type: image/png;
> 	name="unsynched.png"

[skipped]

Please note that being it compressed, it's not so apparent whether the
fields are swapped or not (I assume yes, but it's not clearly visible
in the picture)

/alessandro