[mythtv] Idea for interlaced playback.

[Bjørn Konestabo]

Daniel Kristjansson wrote:

>In anycase bob-deint is the worst filter to use with an interlaced
>monitor, because it doubles the framerate. If some hardware deals
>with this less well than others, then so it is.
>  
>
Not if what I'm playing is 25Hz frames with interlaced fields. :)
Bob gives me separate fields played at 50Hz, which works well on my tv, 
but not
without some loss in spatial fidelity.

>Ah, you are using an analog frame grabber ?
>  
>
I'm using a Hauppauge PVR-150. I also have a PVR-500 which isn't talking 
to me yet.

>>>This is known as an interlaced framebuffer, not "bob and weave".
>>>      
>>>
>>Sorry for being sloppy with the terminology. If what I have described is
>>indeed an interlaced framebuffer, then this is what I want. Simply 
>>pumping the frames out interlaced as they are does not work for me.
>>    
>>
>So basically you need to flip the fields, so that the odd lines are
>are on the odd lines, and even lines are on the even lines?
>  
>
No, this would also only work half the time just the other half. :) . 
It all depends on when I press the play button (or skip). Let's say my
encoder has an odd field affinity. The first (temporally) field is the 
odd one.
(I say temporally, because in the framebuffer, the even and odd fields are
shown together). If I press play at a time the even field is being 
displayed by the tv,
the wrong field is displayed first. 1/50th of a second later the 
odd-field is refreshed
( at the wrong time ) the framebuffer updates, and the same thing 
happens over and over.

Just swapping the fields accomplishes nothing, because  it'd still be 
wrong, only the other 50% of the time.
http://vaggen.net/~bjornko/interlace.php tries to elaborate.

>You should be able to use the same code we use for bob-deint to detect
>if you need to swap the lines odd and even lines. This should be fairly
>easy to do, just look at frame->top_field_first. See calc_bob() in
>VideoOutputXv for an example.
>  
>
Can't seem to find it. I'm guessing it's not in the 0.18.1 source which 
I'm using.

>When you have a patch ready, assign the ticket to me.
>I'd like to improve the video output a bit in 0.20...
>
Sure, I'd love to if I ever get it working. But first I need to get the 
darn thing to build. :)