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Old Feb 8, 2008, 5:44 PM   #21
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NTSC video is 525 vertical by 330 horizontal lines. Only about 480 of those 525 lines are useable, the rest is in the "overscan" portion of the picture on a TV set.

So you have 480 x 330 (60 fps interlaced) to begin with. Who cares if the camera "upconverts" it to 720x480 or higher? It will not matter since it will not look any better than the original source.

More important issue with line input on the 5120a / vupoint dv-da1-vp is the frame rate of only 20 fps. You throw away 1/3 of the frames, bottom line it is not good.

Video input recording needs to be 30 fps to show smooth motion.


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Old Feb 9, 2008, 12:32 AM   #22
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Fox, I appreciate your response. I've taken the 5120A out of my list. Just give me your opinion on the following:

I'm looking to purchase a mobile DVR, like the Archos, that records at either D1 resolution or at least 640 x 480 at 30 fps. I'm going to pair that with a helmet cam that provides either 470 lines of horizontal resolution or 550 lines (bothcams made by the same manufacturer and specs except for the resolution difference).

Would it be worth it to spend the money on the 550 resolution camera or should I just settle for the 470 lines of resolution since most DVR's record using MPEG-4 compression. Would there be that big of a difference in picture quality?

Thanks in advance.
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Old Feb 9, 2008, 8:34 AM   #23
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foxdirtrider wrote:
Quote:
NTSC video is 525 vertical by 330 horizontal lines. Only about 480 of those 525 lines are useable, the rest is in the "overscan" portion of the picture on a TV set.

So you have 480 x 330 (60 fps interlaced) to begin with. Who cares if the camera "upconverts" it to 720x480 or higher? It will not matter since it will not look any better than the original source.
I disagree with some of this. I'll start by agreeing with you on the vertical resolution, everything you said about that is correct. There is no actuall number of pixels defined for NTSC on the horizontal. Because it is an analog signal it can change state at any time from on to off or anywhere in between. Becuase we are so used to computers, we tend to think in terms of pixels. That resolution is pretty much determined by the device(s) using it. a low-end security camera or a VHS VCR can only produce around 300 or less pixels on the horizontal. However, better made devices can definately get over 600 pixels. Most video capture boards can handle up to 720 pixels (although whether there is some scaling going on there is questionable) because of the nature of the signal and the wires it travels on, there is definately an upper-limit to the number of individual pixels that can be generated.

I've said all that to comment on your "who cares" comment. The problem I have with Aiptek's and Digilife's cameras is that they totally discard one of the interlaced fields. That not only cuts your vertical resolution in half, but it also technically halves the frame-rate. (or field rate, whatever you want to call it). And I am 99% convinced the only reason they scale it up is so that nobody can compare their input with other devices that really do record interlaced video and say "Hey look! Aiptek only records at 320x240, where this other camera does 720x480!" In the same way they like to magically increase the number of megapixels the camera can capture. Or how they upscale theframe-rate to 30 fps on their older products. In both cases they expect 99% of the consumers to be too ignorant to be able to tell the difference (and unfortunatly, they are right) so it helps sell their products without worrying about too many people like me knowing the truth.

To I would say "I care" because if I capture video on my computer's internal video capture card, it will look much better and literally have twice or four times the resolution of what the digital camera's input would give me on the same video source.

If anyone thinks I'm out of my mind.. we can do some comparisons. I downloaded that testing DVD yesterday that we discussed in another thread. I can pump that into my video capture card and take some still shots from it. Then someone else can use their camera to record the same shots and we'll compare.
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Old Feb 9, 2008, 11:36 AM   #24
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The worst case of interpolation I ever saw was from an early AGFA camera. Unfortunately I can't seem to find the original review about it on the net, but I am pretty certain it had a 256x256 CCD which was interpolated to 640x480!! It produced terrible photos as you can imagine! Anyone remember the model? That would be considered unacceptable now even in a cheap keychain camera but this was back when even a poor camera wasn't cheap.
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Old Feb 9, 2008, 1:17 PM   #25
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NTSC broadcast TV spec is 525 lines of vertical and 330 lines (max) horizontal. Newer devices like Hi-8, DVD, etc can exceed 330 lines if connected directly to a composite or s-video input.

Don't confuse fields and frames, one NTSC frame (at 30 fps) is made up of two combined fields (60 fields per second). The net effective frame rate is 30 frames per second.

I do not doubt most hybrids toss one field when recording through the A/V input jack. That would reduce the vertical resolution by half. you would end up with a picture resolution of approx 250 (vert) by 330 (horiz).

I have seen stills taken from the MPVR (on this site) and it looks like it does toss one field when recording. You can clearly see jagged "stair step" lines in any diagonal object in the image. The A-HD seems to have a much more "smooth" image, it may correcly handle both frames and give you twice as much vertical resolution from the video input. I only have the A-HD and the Vupoint, so I cannot compare it to the MPVR. I can test the two models I have if anyone is interested.
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Old Feb 9, 2008, 9:22 PM   #26
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I have recorded the "blink" test dvd with both the A-HD and Vupoint dv-da1-vp. Both files are around 110 to 135 mb. Any suggestions to a free web share that accepts files larger than 100mb??
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Old Feb 9, 2008, 9:54 PM   #27
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Post them to Vimeo.com ( its like Youtube but way better ) .. and when you do that the original raw file will be available for download. I will post mine too
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Old Feb 10, 2008, 12:47 AM   #28
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One thing I've noticed is that almost all of the portable DVR units available are being re-badged by different companies selling them and they slap their own model number on them making it difficult to compare specs.



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Old Feb 10, 2008, 4:40 PM   #29
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This is a big headache trying to maintain the Hybrid List. Most of the clones look just like the cameras they're clones of, but I'm not keen to sift through dozens of pictures of the originals to determine which clone is a clone of what. Sometimes it's easy to do, but often not.

Then there's the clones that are restyled enough to look unique. They're impossible to tell from truly original designs. And I'm in no position to determine which camera was built first, so which is the clone of which? And even "unique" ones are just using different sets of components from the same suppliers.

Cameras from the first tier manufacturers rarely have this issue.
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Old Feb 12, 2008, 1:48 PM   #30
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I modified one of these to operate in the closed position and made up a bracket to mount it directly to my helmet. See pic:



I have uploaded some video clips from a dual sport ride last Sunday. It shows the Vupoint dv-da1-vp (same as ddv-5120) recording at 640x480. These are the raw clips, they have not been resized or converted. Original files can be downloaded.

You can see six clips here: http://www.vimeo.com/680288


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