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Artifacts when digitizing DV tapes
Hello,
I am doing some work for a client and they would like me to digitize their home movies that were filmed in mini-DV (720×480 60i).
They don’t have the camera any more but it was filmed in DV-NTSC.I am using a professional DEC to digitize the tapes and using FCP7.0 to do the digitizing. The DEC is an HDV/DV HVR-M154U
I see this strange artifact of jagged lines on the image and I wondered if anyone can tell me why this is so. I have attached the screen shots of the problems that I encounter.
In the first image, you can see the jagged lines on the window in the gymnasium.
In the second image, you can see the jagged edges on the lower railing.Any help or advice on this matter will be greatly appreciated. Thanks!
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3 Replies
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The stair-stepping is called “aliasing”, and was a common issue with standard def video. Are there any artifacts in the overall motion? You want to make sure of the Field Order when capturing.
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That’s actually normal for DV. DV is a 4:1:1 format, and really on the low end of the SD format spectrum. Digibeta, betaSP…those are higher end than DV.
Shane
Little Frog Post
Read my blog, Little Frog in High Def -
It looks like normal DV footage to me (as others have pointed out). You have to realize that NTSC DV only has 480 lines of vertical resolution. If you take a straight line and tilt it, you will see stair steps because there simply isn’t enough resolution to produce a smooth diagonal line. To put it another way, a single DV frame is only 314K pixels. That one third of a mega pixel or 0.3 megapixels. I’m pretty sure that the backup camera on a Prius has more resolution! 😉 (…and I just checked and the back-up camera on a Prius has 520 lines of vertical resolution compared to NTSC DV’s 480! Yikes! )
Are you really “digitizing” these tapes or are you just “capturing” them? I ask because DV tapes are already digital and should be captured via Firewire connection which simply copies the data bit-for-bit from the tape to a file on your hard drive with zero loss. This would give you exactly what the camera recorded. If you are truly digitizing them by playing them back through a digital-to-analog converter only to put the them back through an analog-to-digital converter, you would not be getting the best quality. So if you are using Firewire, you are capturing them, not digitizing them and if you are not using Firewire, you should be for your client’s sake.
~jr
http://www.johnrofrano.com
http://www.vasstsoftware.com
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