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Originally Posted by Dodgexander
Thanks Madshi. Can someone explain what the problem is to me? I have tried to scan through the thread to understand, but have had no success.
So far I notice that the problem relates to "film mode" rather than "video mode".
So film mode presumes theres no deinterlacing?
Video mode presumes there is?
How does this work with pal compared to ntsc?
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In "PAL" video streams (1080i/25 or 576i/25), there's basically only two types of video you can get: true interlaced content (1080i/25 or 576i/25), or progressive content (1080p/25 or 576p/25). With interlaced content you want to deinterlace using the best algorithm available (e.g. vector/motion adaptive) to get a progressive video suitable for display (1080p/50 or 576p/50). For progressive content, you want to simply merge pairs of fields together because they belong to a single frame with no motion (i.e. weave deinterlacing).
However, when you tell a GPU to perform deinterlacing, it
should detect whether the video is actually progressive and thus weave needs to be used rather than vector/motion adaptive. Therefore, you can basically leave deinterlacing on all the time ("video mode") and it'd play back everything perfectly (25p content would be frame-doubled to 50p but this should have no impact on image quality).
Unfortunately, there are apparently some combinations of GPUs and progressive video content where this doesn't happen as intended. Therefore you need to force "film mode" for these to get proper weave deinterlacing so that quality isn't sacrificed by unnecessary vector/motion adaptive deinterlacing.
I don't believe I have any such content (or my GPUs aren't affected) so I can't test this.
Quote:
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Originally Posted by 6233638
Film mode assumes the content is supposed to be deinterlaced as a progressive frame (576p25 using 2:2 rather than 288p50 for example)...
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Again, deinterlacing shouldn't halve vertical resolution. Obviously 576p/50 that has come from a 576i/25 source won't look as good as the 576p/50 original, but it'll look a hell of a lot better than 288p/50. This half-resolution thing is something going wrong and is not the norm for deinterlacing. For what it's worth, I have read that one or two TV models get this wrong too and fail to apply weave properly to progressive material so it's not exclusive to GPUs.