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    Canon XL1 "frame mode" vs DVX100 30p
    #1
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    Can someone point me to an article or discussion about the difference between the XL-1 "frame mode" and the DVX-100 30p mode? I understand there are technical differences between the two, but also what are the practical differences obvious to average viewer? Thanks!

    Kip



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    Re: Canon XL1 "frame mode" vs DVX100 30p
    #2
    Zoomforce
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    xl1 frame mode isnt progressive, it is bloody horrible but for at the time it was revolutionary. The xl1 basically takes 1 interlaced field, and interpolates the other field from a combination of the previous and next frame.. you end up loosing a ton of resolution, and it strobed and pans look horrible... the DVX takes a full progressive frame, much like you would with a digital still camera.

    As for the viewer, the strobing and the panning are very noticable, but they also look like what happens when you take film and tele convert it to NTSC.. so people either love it or hate it.


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    Re: Canon XL1 "frame mode" vs DVX100 30p
    #3
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    "Frame Mode" is a pseudo-progressive scan system. It takes the red & blue data from the even field and the green data from the odd field. The result is about a 25% loss in vertical resolution. So whereas a regular frame from an interlaced video camera has a maximum of about 360 lines of resolution, the XL1 in frame mode delivers about 270 lines. Contrast that with the DVX's pure progressive scan system, which delivers all the data the chip can see on each and every frame. A DVX shows 480 lines of vertical resolution (in NTSC), vs. 270 for the Canon. In other words, the image on the DVX can be nearly twice as sharp as the best the Canon can do in its "frame mode".

    As for panning/strobing, it's basically identical in motion rendering to the 30P mode on the DVX. The red, blue, and green data is all captured in the same moment in time, so motion rendering is the same as 30P, it's just quite a bit softer.

    For the technical description of differences between interlaced, frame mode, and progressive, you can check out this article:
    ftp://ftp.panasonic.com/pub/Panasoni...ressive-WP.pdf


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    Re: Canon XL1 "frame mode" vs DVX100 30p
    #4
    Zoomforce
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    funny you say that Barry..The progressive frames in the XL1 are derived by interpolation from just under 2/3 of the actual field, and most people still believe that the other 1/3 was only a color space. I talked to a Canon Engineer at Nab a few years ago and he told me it wasn't so, they tried it with the GL1 but it caused a horrible color shift. *If there was no interpolation there would not be a resolution loss, as you are creating an entire image from two fields... just samples from two different times. This was what canon was going for but I guess it didn't work out, which is why they had to interpolate, and which is why there is a resolution loss.

    The strobing, is from when it samples a previous frame's field that has moved (panning) so it created a false frame.

    Who knows, I could be wrong as I am basing this on someone else's knowledge..


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    Re: Canon XL1 "frame mode" vs DVX100 30p
    #5
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    I'm basing what I say off of Steve Mullen's article. I've played with the frame mode enough to be able to say that the motion is right, it's clean motion, not "polluted" by extracting data from the alternate field. It's my understanding that the "pixel shift" technique they use is where the green pixel's data is coming from, it's a half-field shifted down on the CCD.

    But everything that goes into a "frame mode" frame is captured in the same 1/30th of a second. It's just really low resolution.


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    Re: Canon XL1 "frame mode" vs DVX100 30p
    #6
    Zoomforce
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    I kinda thought you where refering to pixel shift.. and the pixel shift it the exact reason why they cant do a progressive frame.. because all the CCD's are not sampled the same. The frame mode however, has nothing to do with sampling from different colors, it is an interpolation, I am almost positive about this. I assume canon should say something about this somewhere on thier site.. I will try and go find something.

    The part I am unsure of is the strobing part.. as its not really an interlace problem that you would expect like on stills from an interlaced frame grab.


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    Re: Canon XL1 "frame mode" vs DVX100 30p
    #7
    Shrunk_Monk
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    This is the Videosystems article Steve Mullen wrote, and the one Barry is referring to:


    http://videosystems.com/ar/video_pro...know/index.htm


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    Re: Canon XL1 "frame mode" vs DVX100 30p
    #8
    Zoomforce
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    I gotcha... thanks monk.


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    Re: Canon XL1 "frame mode" vs DVX100 30p
    #9
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    Jarred's right here. The frame mode is created using field info, not color info.

    You can get a good explanation here http://www.dvinfo.net/canon/articles/article57.php

    Not to say Steve Mullen is wrong, but there is alot of misconception to the frame mode as Canon does not give alot of detail about the process.


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    Re: Canon XL1 "frame mode" vs DVX100 30p
    #10
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    Canon doesn't give a lot of info about it because they probably don't understand a lot about it. It's a panasonic invention, not Canon.

    The XL1 Watchdog article is basically claiming that frame mode is nothing more than de-interlacing ("it takes field 2 and interpolates it to make a full frame"). Not only is that contradicted by the Steve Mullen article, but it's also contradicted by the results -- frame mode, lousy as it is, is sharper than de-interlaced footage. According to Mullen's estimate, frame mode can deliver about 320 lines of resolution, vs. the 480 possible in progressive-scan.

    Anyway, the article is there for all to read. The red & blue data is processed separately from the green data, due to the pixel-shift technology. Fields are combined, but because the green data is coming from odd lines and the red & blue data is coming from the even lines, overall resolution is increased (as compared to a simple 1-field de-interlace technique).

    But this has nothing to do with bogus temporal information. I think that's where the confusion is coming in. CCD's don't scan a field at a time -- they scan a full 480 lines at a time (but the recording system can only record out 240 lines). So a CCD samples motion 60 times a second, and then records it out as a half-frame, 60 times a second. In Frame Mode, it samples the motion 30 times a second -- for the second field, it just dumps the same contents out of its buffer, instead of re-sampling.

    So you're not getting combined data from odd & even fields that have been sampled at different times (which would cause horrible strobing artifacting if you were!) You're getting data combined from odd & even fields THAT WERE RECORDED IN THE SAME 1/60th INSTANT IN TIME. Which is why it's temporally correct motion sampling, equivalent to 30P on the DVX. But because the frame is being captured on an interlaced CCD, row-pair summation reduces the potential resolution to 360 lines, and then the frame-mode interpolation further reduces it to 320 lines, whereas on the DVX you'll get the same temporal motion but have a full 480 lines.


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