pal interlaced crawl

[smok3]

iam having a problem encoding a progressive material (film telecine) with interlaced subtitle (fast, small crawl).
idea is to achive a decent readability of the crawl on the lcd screens as well.

a. any suggestions on selecting the proper encoder? (i have tested hc017 and some hardware coder, where hc does look a lot better, but still not there yet.)
b. or maybe better, what computer player with what settings will give decent results on computer lcd screens?

[Mug Funky]

you'll have to set your LCD's refresh rate to be in sync with the field rate of your scrolling captions. that means 60Hz for NTSC, and god knows what for PAL because AFAIK there's no multiples of 50 on any LCD i've tried. if you make it progressive PAL you can set to 75Hz as that's 3 refreshes per PAL frame. but on 50Hz stuff you'll get stutter no matter what.

as far as what encoder to use with what settings, that depends far too strongly on the type of material you're encoding. try it with defaults and replace any parts that go bad with more conservative settings (less b-frames and increasing bitrate for just that segment usually helps. in extreme cases i've had to disable b-frames altogether and perform heavy filtering on target areas. that was fun:))

[edit]

quite obviously your player software will need some kind of adaptive deinterlace. also, auto-3:2 is out of the question because it'll either be completely ineffective or bugger up the scrolling text. you'll have to settle for motion-adaptive bobbing, or just a dumb bob even. LCD screens tend to have enough lag time to allow dumb bob without being overtly flickery.

[foxyshadis]

I think many LCDs actually have 100 Hz and 120 Hz, especially higher-end ones, but you need a custom driver for nvidia and ati cards to be able to use more than 60 you're usually limited to. (I set mine to 90 or 100 depending.) For integrated chipsets I don't think you'd have that option at all. The Omega drivers are well-respected modded versions.

[scharfis_brain]

IMO there are no TFT-Screens that are able to understand more than 85 Hertz. Everything above this will yield into the well known "Out of frequency range" Message on your screen.

But soe displays do understand 50 Hertz. You need powerstrip or some other tweaker to set it up.

[colinb]

Sorry if I'm being stupid, but does this mean that there are currently no LCDs which can display interlaced PAL properly?

What do LCD screen do with interlaced PAL if they can not be set to 50 Hz or 100 Hz?

[Doom9]

does this mean that there are currently no LCDs which can display interlaced PAL properly?Simply put, yes. That's because LCDs are inheritently progressive (anything good is.. interlaced is an evil piece of decade year old technology that should be abolished).. so anything that is being displayed there has to be turned into something progressive, irrespective of any refresh rates.

[Kika]

Most of the newer LCD-Displays are able to work at 50Hz.

[colinb]

That's because LCDs are inheritently progressive ... so anything that is being displayed there has to be turned into something progressive, irrespective of any refresh rates.

Does that mean that LCDs will perform deinterlacing on interlaced source and then try to display the resulting progressive frames as best they can depending on what refresh rate they are set to?

So if you could set your LCD to 50Hz and fed it with PAL interlaced source would you get:

- 50 *unique* progressive frames per sec, or
- 50 progressive frames per sec with identical pairs (which would look like 25 progressive frames per sec)

[Doom9]

Does that mean that LCDs will perform deinterlacing on interlaced source and then try to display the resulting progressive frames as best they can depending on what refresh rate they are set to?For PC displays, not at all.. PC displays, for many generations, have only supported progressive input. Whatever you see on a pc display is progressive. when a software plays interlaced content, it can either do nothing about it (and you'll be able to see how interlaced means half pictures.. every second line will be black), or the software can deinterlace (the results depend in the software and algorithms).

- 50 *unique* progressive frames per sec, or
- 50 progressive frames per sec with identical pairs (which would look like 25 progressive frames per sec)neither.. assuming the software doesn't do any deinterlacing, you'll end up with 50 unique frames.. each having half the lines blank. don't forget.. there's no such thing as interlacing on any pc display.

[smok3]

tnx for all the aswers,

how come there is still such a big difference between 85Hz CRT vs 85Hz LCD?

[foxyshadis]

LCD displays fairly instantaneously and doesn't have short falloff times like crt. However, the long falloff means it also means a lot more motion-blurring, so that even if the pixels can be updated that fast, they don't actually change that fast. (They sorta half-change.) Most LCDs are designed for 60 fps or lower, and only the highest-end can produce 80-120 with anything near the clarity of a good trinitron.

Response time is the usual way of measuring it, 20 ms response time means 50 hz, 14 ms is 72 Hz. It does seem that they ghost below that anyway, so maybe it means something other than "time from one clean image to another". Or maybe it's my slow eyes and brain causing the ghosting. :p

[colinb]

assuming the software doesn't do any deinterlacing, you'll end up with 50 unique frames.. each having half the lines blank. don't forget.. there's no such thing as interlacing on any pc display.

I see what you mean about software players running on a PC, but what about LCD TVs?

Presumably they are optimised to handle interlaced PAL. So I'd like to ask the same questions with respect to LCD TVs:


Does that mean that LCD TV's will perform deinterlacing on interlaced source and then try to display the resulting progressive frames as best they can depending on what refresh rate they are set to?

So if you could set your LCD to 50Hz and fed it with PAL interlaced source would you get:

- 50 *unique* progressive frames per sec, or
- 50 progressive frames per sec with identical pairs (which would look like 25 progressive frames per sec)

[foxyshadis]

If something is labeled "progressive scan" it usually has some form of deinterlacing and/or ivtc, anything from dumb bob to kernel to adaptive interpolation. There's some brand out there that gives high-quality interpolation including mild motion compensation, but I don't recall it. ($$$$.)

[smok3]

yeah response time, however i noticed on my dell LCD that black areas seem to have longer 'stayon time' (or how is that called) than brighter, especially noticable when watching movies for some reason - on cuts (never noticed that on games thought...)

[Doom9]

but what about LCD TVs?There, you have a built-in deinterlacer.. any interlaced input will be put through that. So instead of having 50 frames that have every second line black, you get whatever result the deinterlacer manages to produce. It is still progressive in every single case though.
In the Matrix "there is no spoon", on LCD displays "there is no interlacing".
But if your LCD has progressive scan inputs, even if analog, the signal should bypass the deinterlacer and be displayed directly. This obviously also holds for any digital input (so via DVI you can reproduce the whole 50 frames with every second line black scenario).

[foxyshadis]

Is that how it works, Doom9? I always thought it was the opposite. Thanks for clarifying!