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assiduous
Account closed
Registered: Jun 2007
Posts: 343 |
saving the screen
hi
I seek some way to save the screen on a real C64. I need to save everything from the screen (or asmuch as possible). Im equipped with Action Replay7 and i have already tried to tamper with the freezer options but it seems that with freezing certain elements from the screen are lost like raster bars or other effects. i also tried using the backup option in AR7 which saves the executable of the frozen C64 state but that doesnt seem to save the necessary elements of the screen either (they are generated in the next frame after executing the snapshot and thats not what Im after).
thx for any help. |
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JackAsser
Registered: Jun 2002
Posts: 1989 |
Quote: Most capture devices "deinterlace" even progressive signals down to 25 fps, either by blurring or by weaving. Some do proper 50 fps, but it tend to be undocumented, so it's a little hit and miss...
It's indeed hit and miss. However if the device de-interlaces using weaving and the SW don't compress the result too heavily there are some hopes left. It's quite simple to extract the odd / even raster lines from a weaved frame and simply stretch the two fields to double height. This will give you back the original 50 fps progressive stream.
A problem of course if a capture device without any intelligence simply assumes the progressive stream is interlaces is first field top or not. During removal of weaving you might get temporal problems. I.e. odd lines belonging to frame x and even lines belonging to frame x+1 but you mix them up. This you'll notice immediately of course and if the capture device behaves the same always, then simply reverse field order during the process. |
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assiduous
Account closed
Registered: Jun 2007
Posts: 343 |
one of the effects involves a peculiar sideborder colour logic so black & white output wouldnt be very useful as a fact :)
theres no need for a crystal clear output,just clear enough to allow to precisely count hires pixels and verify what colour they are. I will have to find out more about devices that enable true vid capturing 50FPS progressive. |
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assiduous
Account closed
Registered: Jun 2007
Posts: 343 |
i attempted several times with various search phrases on google but i was unable to find any tv card that allows to capture a 50 FPS progressive video stream. if anyone more experienced in this field knows of such device ( MagerValp? ) then please let me know. costs dont matter. |
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MagerValp
Registered: Dec 2001
Posts: 1055 |
"50 fps" video capture yields a few good hits, including:
http://www.epixinc.com/products/pixci_sv.htm
http://www.geovision.com.tw/english/product/GV-650.htm
They don't come cheap though...
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Radiant
Registered: Sep 2004
Posts: 639 |
This thread might be interesting. I don't think those expensive cards are necessary (they seem to be aimed at a different target audience altogether).
The question is then, which cards can capture an interlaced stream without deinterlacing it? |
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JackAsser
Registered: Jun 2002
Posts: 1989 |
Quote: This thread might be interesting. I don't think those expensive cards are necessary (they seem to be aimed at a different target audience altogether).
The question is then, which cards can capture an interlaced stream without deinterlacing it?
As I said before; cards that capture in 25fps, i.e. deinterlace usually do this using the weaving method. Saving as loss-less data and then simply re-interlace shouldn't be any problems what so ever. Might take some coding effort but that's all. ;D |
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MagerValp
Registered: Dec 2001
Posts: 1055 |
Indeed, it's a software & driver problem. Since the hardware obviously grabs 50 fields per second, the problem is just getting it to output it as a progressive stream.
What about those open source drivers for BT chips?
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assiduous
Account closed
Registered: Jun 2007
Posts: 343 |
what do you mean by saving as lossless data ? the cards are usually made for capturing 50 fps interlace (or 25 fps progressive) stream,in other words they capture half of the vertical resolution of each frame because they compose each frame of 2 adjacent ones. Thats how i believe it works:
1st captured frame:
1st line: 1st C64 frame
2nd line: 2nd C64 frame
3rd line: 1st C64 frame
4th line: 2nd C64 frame
(...)
2nd captured grame:
1st line: 3rd C64 frame
2nd line: 4th C64 frame
3rd line: 3rd C64 frame
4th line: 4th C64 frame
(...)
Theres no way you can get 50 fps progressive stream in the full resolution using such cards. From the link that MagerValp posted ( http://www.epixinc.com/products/pixci_sv.htm ):
"CAPTURE OPTIONS
Capture FIELDs to Double the Capture Rate: If fast capture rate is more important than vertical resolution, then selecting the Field at Field mode doubles a field capture rate while cutting vertical resolution in half. Capture 50 fields per second from a PAL or CCIR camera; capture 60 fields per second from an NTSC or RS-170 camera."
The other link doesnt even mention if the card grabs 50 FPS interlaced or progressive so its rather likely it captures every second line.
apparently you cant do that without a hardware that captures a 50 fps progressive stream natively. if it is possible to get it to grab more vertical resolution than it specified for by using specific software/modified drivers then please post some links as I havent found anything like that |
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MagerValp
Registered: Dec 2001
Posts: 1055 |
Like I wrote earlier in the thread you'll never find it by reading documentation. You have to get a card and play with the driver settings, and if you're lucky you'll get it to capture at 50 fps progressive.
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assiduous
Account closed
Registered: Jun 2007
Posts: 343 |
finally theres a light at the end of the tunnel:) it seems that my understanding of the subject was slightly wrong- i was seeing the C64 output as 403x284 which is abit misleading. ive gained some knowledge on how PAL works and now the point of reference is 768x576. it appears that using a recording device capable of capturing half a vertical resolution at a progressive rate i could grab upto 768x288. speaking of the vertical resolution it should be actually sufficient seeing as the VIC article of Christian Bauer defines the number of visible lines as 284.
heres the post that helped me alittle to grasp the idea:
Quote:All TV's I've seen support a non-interlaced mode - a kind of 288p with a full 50Hz refresh rate if you will.
It was used extensively by older computers and video game systems. On some, such as the Atari ST or the commodore amiga you could use interlace mode and use the other 288 lines, if you wanted, at the expense of flicker (but you gained higher resolution). |
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