[linux-dvb] Re: kernel-dvb and tvtime

[Michael Hunold <hunold@convergence.de>]

Hello Billy,

>   It sounds like the driver is giving bottom-field-first frames instead
> of top-field-first.
To be honest: it's undefined, if you specify V4L2_FIELD_INTERLACED or 
V4L2_FIELD_ANY. But it's possible that I screwed up somewhere within my 
capture engine.

>   In the V4L2 spec it says something about "PAL interlaced is bff" but I
> didn't believe it (it doesn't make logical sense to me to change it for
> PAL).
Sounds bogus to me, too.

>   So, um, what's the deal?  If you do give bff frames, do you indicate
> that somewhere?
No, not currently. My driver supports currently

V4L2_FIELD_TOP
V4L2_FIELD_BOTTOM
V4L2_FIELD_INTERLACED
V4L2_FIELD_ALTERNATE

TOP and BOTTOM are useless for you, because the other field is lost.
When using interlaced, the field order is undefined.

Please have a look at http://bytesex.org/v4l/spec/x3565.html.

I think that capturing fields into separate buffers with 
V4L2_FIELD_ALTERNATE is the best for you, is it?

>   -Billy
CU
Michael.




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