[mythtv] bobdeint observation
John Patrick Poet
john at BlueSkyTours.com
Wed Sep 1 21:57:44 EDT 2004
Doug Larrick wrote:
> Isaac Richards wrote:
>
>> On Saturday 28 August 2004 01:17 am, Andy McMullan wrote:
>>
>>> Basically all this does is draw the second field one pixel lower than
>>> the first field. The effect is pretty subtle, but I'm pretty sure it
>>> gives a better result.
>>
>>
>> I've had this (well, same idea) in my tree for a couple weeks now.
>> It does actually make video playback look very good on my (ntsc,
>> fx5200) tv-out, but the OSD still looks bad. Haven't had time to
>> mess with it much, though.
>
>
> The attached patch seems to get it right for both top-first and
> bottom-first videos for me. For HDTV, it doesn't seem to make much
> difference since the fields are so big to begin with. But for
> standard-def stuff it does make a difference.
>
> The reason the OSD looks bad is that it's being drawn onto a surface
> with only half the normal vertical resolution (one field). In order
> to make it look nice, you'd have to do one of:
> * double the scanlines in software into a full-height Xv buffer before
> rendering the OSD onto it
> * arrange for the filter to output two full-height frames rather than
> the current way of using the top half for the top field and the bottom
> half for the bottom field. I avoided this approach to keep from
> complicating the filter interface; doing so, though, would allow
> adoption of some of the more advanced deinterlace filters from e.g.
> TvTime
> * figure out how to render the OSD in an interlaced manner, sending
> the appropriate OSD scanlines to the appropriate fields in the video.
>
> -Doug
I briefly had a PVR-350 in my system. Video quality was poor compared
to my old ReplayTVs. Tried this patch and it made a very nice
improvement. I can recommend this patch to those using PVR-x50 cards.
John
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